diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/__pycache__/threshold.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/__pycache__/threshold.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..bd7774258d5ba0b2e2e778f8f5c23f59a68db07f Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/__pycache__/threshold.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__init__.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__init__.py new file mode 100644 index 0000000000000000000000000000000000000000..c5d19abed99501086359c87670edc31a680fe36c --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__init__.py @@ -0,0 +1,11 @@ +from .maxflow import * +from .mincost import * +from .boykovkolmogorov import * +from .dinitz_alg import * +from .edmondskarp import * +from .gomory_hu import * +from .preflowpush import * +from .shortestaugmentingpath import * +from .capacityscaling import * +from .networksimplex import * +from .utils import build_flow_dict, build_residual_network diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__pycache__/boykovkolmogorov.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__pycache__/boykovkolmogorov.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..ec5762eea2183ef671343a24d170ebfb13b5f732 Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__pycache__/boykovkolmogorov.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__pycache__/capacityscaling.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/__pycache__/capacityscaling.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..0691c8e93e77391fa917dbe51f774e422deb5279 Binary files 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Boykov-Kolmogorov algorithm. + + This function returns the residual network resulting after computing + the maximum flow. See below for details about the conventions + NetworkX uses for defining residual networks. + + This algorithm has worse case complexity $O(n^2 m |C|)$ for $n$ nodes, $m$ + edges, and $|C|$ the cost of the minimum cut [1]_. This implementation + uses the marking heuristic defined in [2]_ which improves its running + time in many practical problems. + + Parameters + ---------- + G : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + s : node + Source node for the flow. + + t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + residual : NetworkX graph + Residual network on which the algorithm is to be executed. If None, a + new residual network is created. Default value: None. + + value_only : bool + If True compute only the value of the maximum flow. This parameter + will be ignored by this algorithm because it is not applicable. + + cutoff : integer, float + If specified, the algorithm will terminate when the flow value reaches + or exceeds the cutoff. In this case, it may be unable to immediately + determine a minimum cut. Default value: None. + + Returns + ------- + R : NetworkX DiGraph + Residual network after computing the maximum flow. + + Raises + ------ + NetworkXError + The algorithm does not support MultiGraph and MultiDiGraph. If + the input graph is an instance of one of these two classes, a + NetworkXError is raised. + + NetworkXUnbounded + If the graph has a path of infinite capacity, the value of a + feasible flow on the graph is unbounded above and the function + raises a NetworkXUnbounded. + + See also + -------- + :meth:`maximum_flow` + :meth:`minimum_cut` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. If :samp:`cutoff` is not + specified, reachability to :samp:`t` using only edges :samp:`(u, v)` such + that :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Examples + -------- + >>> from networkx.algorithms.flow import boykov_kolmogorov + + The functions that implement flow algorithms and output a residual + network, such as this one, are not imported to the base NetworkX + namespace, so you have to explicitly import them from the flow package. + + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + >>> R = boykov_kolmogorov(G, "x", "y") + >>> flow_value = nx.maximum_flow_value(G, "x", "y") + >>> flow_value + 3.0 + >>> flow_value == R.graph["flow_value"] + True + + A nice feature of the Boykov-Kolmogorov algorithm is that a partition + of the nodes that defines a minimum cut can be easily computed based + on the search trees used during the algorithm. These trees are stored + in the graph attribute `trees` of the residual network. + + >>> source_tree, target_tree = R.graph["trees"] + >>> partition = (set(source_tree), set(G) - set(source_tree)) + + Or equivalently: + + >>> partition = (set(G) - set(target_tree), set(target_tree)) + + References + ---------- + .. [1] Boykov, Y., & Kolmogorov, V. (2004). An experimental comparison + of min-cut/max-flow algorithms for energy minimization in vision. + Pattern Analysis and Machine Intelligence, IEEE Transactions on, + 26(9), 1124-1137. + https://doi.org/10.1109/TPAMI.2004.60 + + .. [2] Vladimir Kolmogorov. Graph-based Algorithms for Multi-camera + Reconstruction Problem. PhD thesis, Cornell University, CS Department, + 2003. pp. 109-114. + https://web.archive.org/web/20170809091249/https://pub.ist.ac.at/~vnk/papers/thesis.pdf + + """ + R = boykov_kolmogorov_impl(G, s, t, capacity, residual, cutoff) + R.graph["algorithm"] = "boykov_kolmogorov" + nx._clear_cache(R) + return R + + +def boykov_kolmogorov_impl(G, s, t, capacity, residual, cutoff): + if s not in G: + raise nx.NetworkXError(f"node {str(s)} not in graph") + if t not in G: + raise nx.NetworkXError(f"node {str(t)} not in graph") + if s == t: + raise nx.NetworkXError("source and sink are the same node") + + if residual is None: + R = build_residual_network(G, capacity) + else: + R = residual + + # Initialize/reset the residual network. + # This is way too slow + # nx.set_edge_attributes(R, 0, 'flow') + for u in R: + for e in R[u].values(): + e["flow"] = 0 + + # Use an arbitrary high value as infinite. It is computed + # when building the residual network. + INF = R.graph["inf"] + + if cutoff is None: + cutoff = INF + + R_succ = R.succ + R_pred = R.pred + + def grow(): + """Bidirectional breadth-first search for the growth stage. + + Returns a connecting edge, that is and edge that connects + a node from the source search tree with a node from the + target search tree. + The first node in the connecting edge is always from the + source tree and the last node from the target tree. + """ + while active: + u = active[0] + if u in source_tree: + this_tree = source_tree + other_tree = target_tree + neighbors = R_succ + else: + this_tree = target_tree + other_tree = source_tree + neighbors = R_pred + for v, attr in neighbors[u].items(): + if attr["capacity"] - attr["flow"] > 0: + if v not in this_tree: + if v in other_tree: + return (u, v) if this_tree is source_tree else (v, u) + this_tree[v] = u + dist[v] = dist[u] + 1 + timestamp[v] = timestamp[u] + active.append(v) + elif v in this_tree and _is_closer(u, v): + this_tree[v] = u + dist[v] = dist[u] + 1 + timestamp[v] = timestamp[u] + _ = active.popleft() + return None, None + + def augment(u, v): + """Augmentation stage. + + Reconstruct path and determine its residual capacity. + We start from a connecting edge, which links a node + from the source tree to a node from the target tree. + The connecting edge is the output of the grow function + and the input of this function. + """ + attr = R_succ[u][v] + flow = min(INF, attr["capacity"] - attr["flow"]) + path = [u] + # Trace a path from u to s in source_tree. + w = u + while w != s: + n = w + w = source_tree[n] + attr = R_pred[n][w] + flow = min(flow, attr["capacity"] - attr["flow"]) + path.append(w) + path.reverse() + # Trace a path from v to t in target_tree. + path.append(v) + w = v + while w != t: + n = w + w = target_tree[n] + attr = R_succ[n][w] + flow = min(flow, attr["capacity"] - attr["flow"]) + path.append(w) + # Augment flow along the path and check for saturated edges. + it = iter(path) + u = next(it) + these_orphans = [] + for v in it: + R_succ[u][v]["flow"] += flow + R_succ[v][u]["flow"] -= flow + if R_succ[u][v]["flow"] == R_succ[u][v]["capacity"]: + if v in source_tree: + source_tree[v] = None + these_orphans.append(v) + if u in target_tree: + target_tree[u] = None + these_orphans.append(u) + u = v + orphans.extend(sorted(these_orphans, key=dist.get)) + return flow + + def adopt(): + """Adoption stage. + + Reconstruct search trees by adopting or discarding orphans. + During augmentation stage some edges got saturated and thus + the source and target search trees broke down to forests, with + orphans as roots of some of its trees. We have to reconstruct + the search trees rooted to source and target before we can grow + them again. + """ + while orphans: + u = orphans.popleft() + if u in source_tree: + tree = source_tree + neighbors = R_pred + else: + tree = target_tree + neighbors = R_succ + nbrs = ((n, attr, dist[n]) for n, attr in neighbors[u].items() if n in tree) + for v, attr, d in sorted(nbrs, key=itemgetter(2)): + if attr["capacity"] - attr["flow"] > 0: + if _has_valid_root(v, tree): + tree[u] = v + dist[u] = dist[v] + 1 + timestamp[u] = time + break + else: + nbrs = ( + (n, attr, dist[n]) for n, attr in neighbors[u].items() if n in tree + ) + for v, attr, d in sorted(nbrs, key=itemgetter(2)): + if attr["capacity"] - attr["flow"] > 0: + if v not in active: + active.append(v) + if tree[v] == u: + tree[v] = None + orphans.appendleft(v) + if u in active: + active.remove(u) + del tree[u] + + def _has_valid_root(n, tree): + path = [] + v = n + while v is not None: + path.append(v) + if v in (s, t): + base_dist = 0 + break + elif timestamp[v] == time: + base_dist = dist[v] + break + v = tree[v] + else: + return False + length = len(path) + for i, u in enumerate(path, 1): + dist[u] = base_dist + length - i + timestamp[u] = time + return True + + def _is_closer(u, v): + return timestamp[v] <= timestamp[u] and dist[v] > dist[u] + 1 + + source_tree = {s: None} + target_tree = {t: None} + active = deque([s, t]) + orphans = deque() + flow_value = 0 + # data structures for the marking heuristic + time = 1 + timestamp = {s: time, t: time} + dist = {s: 0, t: 0} + while flow_value < cutoff: + # Growth stage + u, v = grow() + if u is None: + break + time += 1 + # Augmentation stage + flow_value += augment(u, v) + # Adoption stage + adopt() + + if flow_value * 2 > INF: + raise nx.NetworkXUnbounded("Infinite capacity path, flow unbounded above.") + + # Add source and target tree in a graph attribute. + # A partition that defines a minimum cut can be directly + # computed from the search trees as explained in the docstrings. + R.graph["trees"] = (source_tree, target_tree) + # Add the standard flow_value graph attribute. + R.graph["flow_value"] = flow_value + return R diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/capacityscaling.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/capacityscaling.py new file mode 100644 index 0000000000000000000000000000000000000000..bf68565c5486bb7b60e7ddcf6089e448bc6ddef1 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/capacityscaling.py @@ -0,0 +1,407 @@ +""" +Capacity scaling minimum cost flow algorithm. +""" + +__all__ = ["capacity_scaling"] + +from itertools import chain +from math import log + +import networkx as nx + +from ...utils import BinaryHeap, arbitrary_element, not_implemented_for + + +def _detect_unboundedness(R): + """Detect infinite-capacity negative cycles.""" + G = nx.DiGraph() + G.add_nodes_from(R) + + # Value simulating infinity. + inf = R.graph["inf"] + # True infinity. + f_inf = float("inf") + for u in R: + for v, e in R[u].items(): + # Compute the minimum weight of infinite-capacity (u, v) edges. + w = f_inf + for k, e in e.items(): + if e["capacity"] == inf: + w = min(w, e["weight"]) + if w != f_inf: + G.add_edge(u, v, weight=w) + + if nx.negative_edge_cycle(G): + raise nx.NetworkXUnbounded( + "Negative cost cycle of infinite capacity found. " + "Min cost flow may be unbounded below." + ) + + +@not_implemented_for("undirected") +def _build_residual_network(G, demand, capacity, weight): + """Build a residual network and initialize a zero flow.""" + if sum(G.nodes[u].get(demand, 0) for u in G) != 0: + raise nx.NetworkXUnfeasible("Sum of the demands should be 0.") + + R = nx.MultiDiGraph() + R.add_nodes_from( + (u, {"excess": -G.nodes[u].get(demand, 0), "potential": 0}) for u in G + ) + + inf = float("inf") + # Detect selfloops with infinite capacities and negative weights. + for u, v, e in nx.selfloop_edges(G, data=True): + if e.get(weight, 0) < 0 and e.get(capacity, inf) == inf: + raise nx.NetworkXUnbounded( + "Negative cost cycle of infinite capacity found. " + "Min cost flow may be unbounded below." + ) + + # Extract edges with positive capacities. Self loops excluded. + if G.is_multigraph(): + edge_list = [ + (u, v, k, e) + for u, v, k, e in G.edges(data=True, keys=True) + if u != v and e.get(capacity, inf) > 0 + ] + else: + edge_list = [ + (u, v, 0, e) + for u, v, e in G.edges(data=True) + if u != v and e.get(capacity, inf) > 0 + ] + # Simulate infinity with the larger of the sum of absolute node imbalances + # the sum of finite edge capacities or any positive value if both sums are + # zero. This allows the infinite-capacity edges to be distinguished for + # unboundedness detection and directly participate in residual capacity + # calculation. + inf = ( + max( + sum(abs(R.nodes[u]["excess"]) for u in R), + 2 + * sum( + e[capacity] + for u, v, k, e in edge_list + if capacity in e and e[capacity] != inf + ), + ) + or 1 + ) + for u, v, k, e in edge_list: + r = min(e.get(capacity, inf), inf) + w = e.get(weight, 0) + # Add both (u, v) and (v, u) into the residual network marked with the + # original key. (key[1] == True) indicates the (u, v) is in the + # original network. + R.add_edge(u, v, key=(k, True), capacity=r, weight=w, flow=0) + R.add_edge(v, u, key=(k, False), capacity=0, weight=-w, flow=0) + + # Record the value simulating infinity. + R.graph["inf"] = inf + + _detect_unboundedness(R) + + return R + + +def _build_flow_dict(G, R, capacity, weight): + """Build a flow dictionary from a residual network.""" + inf = float("inf") + flow_dict = {} + if G.is_multigraph(): + for u in G: + flow_dict[u] = {} + for v, es in G[u].items(): + flow_dict[u][v] = { + # Always saturate negative selfloops. + k: ( + 0 + if ( + u != v or e.get(capacity, inf) <= 0 or e.get(weight, 0) >= 0 + ) + else e[capacity] + ) + for k, e in es.items() + } + for v, es in R[u].items(): + if v in flow_dict[u]: + flow_dict[u][v].update( + (k[0], e["flow"]) for k, e in es.items() if e["flow"] > 0 + ) + else: + for u in G: + flow_dict[u] = { + # Always saturate negative selfloops. + v: ( + 0 + if (u != v or e.get(capacity, inf) <= 0 or e.get(weight, 0) >= 0) + else e[capacity] + ) + for v, e in G[u].items() + } + flow_dict[u].update( + (v, e["flow"]) + for v, es in R[u].items() + for e in es.values() + if e["flow"] > 0 + ) + return flow_dict + + +@nx._dispatchable( + node_attrs="demand", edge_attrs={"capacity": float("inf"), "weight": 0} +) +def capacity_scaling( + G, demand="demand", capacity="capacity", weight="weight", heap=BinaryHeap +): + r"""Find a minimum cost flow satisfying all demands in digraph G. + + This is a capacity scaling successive shortest augmenting path algorithm. + + G is a digraph with edge costs and capacities and in which nodes + have demand, i.e., they want to send or receive some amount of + flow. A negative demand means that the node wants to send flow, a + positive demand means that the node want to receive flow. A flow on + the digraph G satisfies all demand if the net flow into each node + is equal to the demand of that node. + + Parameters + ---------- + G : NetworkX graph + DiGraph or MultiDiGraph on which a minimum cost flow satisfying all + demands is to be found. + + demand : string + Nodes of the graph G are expected to have an attribute demand + that indicates how much flow a node wants to send (negative + demand) or receive (positive demand). Note that the sum of the + demands should be 0 otherwise the problem in not feasible. If + this attribute is not present, a node is considered to have 0 + demand. Default value: 'demand'. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + weight : string + Edges of the graph G are expected to have an attribute weight + that indicates the cost incurred by sending one unit of flow on + that edge. If not present, the weight is considered to be 0. + Default value: 'weight'. + + heap : class + Type of heap to be used in the algorithm. It should be a subclass of + :class:`MinHeap` or implement a compatible interface. + + If a stock heap implementation is to be used, :class:`BinaryHeap` is + recommended over :class:`PairingHeap` for Python implementations without + optimized attribute accesses (e.g., CPython) despite a slower + asymptotic running time. For Python implementations with optimized + attribute accesses (e.g., PyPy), :class:`PairingHeap` provides better + performance. Default value: :class:`BinaryHeap`. + + Returns + ------- + flowCost : integer + Cost of a minimum cost flow satisfying all demands. + + flowDict : dictionary + If G is a digraph, a dict-of-dicts keyed by nodes such that + flowDict[u][v] is the flow on edge (u, v). + If G is a MultiDiGraph, a dict-of-dicts-of-dicts keyed by nodes + so that flowDict[u][v][key] is the flow on edge (u, v, key). + + Raises + ------ + NetworkXError + This exception is raised if the input graph is not directed, + not connected. + + NetworkXUnfeasible + This exception is raised in the following situations: + + * The sum of the demands is not zero. Then, there is no + flow satisfying all demands. + * There is no flow satisfying all demand. + + NetworkXUnbounded + This exception is raised if the digraph G has a cycle of + negative cost and infinite capacity. Then, the cost of a flow + satisfying all demands is unbounded below. + + Notes + ----- + This algorithm does not work if edge weights are floating-point numbers. + + See also + -------- + :meth:`network_simplex` + + Examples + -------- + A simple example of a min cost flow problem. + + >>> G = nx.DiGraph() + >>> G.add_node("a", demand=-5) + >>> G.add_node("d", demand=5) + >>> G.add_edge("a", "b", weight=3, capacity=4) + >>> G.add_edge("a", "c", weight=6, capacity=10) + >>> G.add_edge("b", "d", weight=1, capacity=9) + >>> G.add_edge("c", "d", weight=2, capacity=5) + >>> flowCost, flowDict = nx.capacity_scaling(G) + >>> flowCost + 24 + >>> flowDict + {'a': {'b': 4, 'c': 1}, 'd': {}, 'b': {'d': 4}, 'c': {'d': 1}} + + It is possible to change the name of the attributes used for the + algorithm. + + >>> G = nx.DiGraph() + >>> G.add_node("p", spam=-4) + >>> G.add_node("q", spam=2) + >>> G.add_node("a", spam=-2) + >>> G.add_node("d", spam=-1) + >>> G.add_node("t", spam=2) + >>> G.add_node("w", spam=3) + >>> G.add_edge("p", "q", cost=7, vacancies=5) + >>> G.add_edge("p", "a", cost=1, vacancies=4) + >>> G.add_edge("q", "d", cost=2, vacancies=3) + >>> G.add_edge("t", "q", cost=1, vacancies=2) + >>> G.add_edge("a", "t", cost=2, vacancies=4) + >>> G.add_edge("d", "w", cost=3, vacancies=4) + >>> G.add_edge("t", "w", cost=4, vacancies=1) + >>> flowCost, flowDict = nx.capacity_scaling( + ... G, demand="spam", capacity="vacancies", weight="cost" + ... ) + >>> flowCost + 37 + >>> flowDict + {'p': {'q': 2, 'a': 2}, 'q': {'d': 1}, 'a': {'t': 4}, 'd': {'w': 2}, 't': {'q': 1, 'w': 1}, 'w': {}} + """ + R = _build_residual_network(G, demand, capacity, weight) + + inf = float("inf") + # Account cost of negative selfloops. + flow_cost = sum( + 0 + if e.get(capacity, inf) <= 0 or e.get(weight, 0) >= 0 + else e[capacity] * e[weight] + for u, v, e in nx.selfloop_edges(G, data=True) + ) + + # Determine the maximum edge capacity. + wmax = max(chain([-inf], (e["capacity"] for u, v, e in R.edges(data=True)))) + if wmax == -inf: + # Residual network has no edges. + return flow_cost, _build_flow_dict(G, R, capacity, weight) + + R_nodes = R.nodes + R_succ = R.succ + + delta = 2 ** int(log(wmax, 2)) + while delta >= 1: + # Saturate Δ-residual edges with negative reduced costs to achieve + # Δ-optimality. + for u in R: + p_u = R_nodes[u]["potential"] + for v, es in R_succ[u].items(): + for k, e in es.items(): + flow = e["capacity"] - e["flow"] + if e["weight"] - p_u + R_nodes[v]["potential"] < 0: + flow = e["capacity"] - e["flow"] + if flow >= delta: + e["flow"] += flow + R_succ[v][u][(k[0], not k[1])]["flow"] -= flow + R_nodes[u]["excess"] -= flow + R_nodes[v]["excess"] += flow + # Determine the Δ-active nodes. + S = set() + T = set() + S_add = S.add + S_remove = S.remove + T_add = T.add + T_remove = T.remove + for u in R: + excess = R_nodes[u]["excess"] + if excess >= delta: + S_add(u) + elif excess <= -delta: + T_add(u) + # Repeatedly augment flow from S to T along shortest paths until + # Δ-feasibility is achieved. + while S and T: + s = arbitrary_element(S) + t = None + # Search for a shortest path in terms of reduce costs from s to + # any t in T in the Δ-residual network. + d = {} + pred = {s: None} + h = heap() + h_insert = h.insert + h_get = h.get + h_insert(s, 0) + while h: + u, d_u = h.pop() + d[u] = d_u + if u in T: + # Path found. + t = u + break + p_u = R_nodes[u]["potential"] + for v, es in R_succ[u].items(): + if v in d: + continue + wmin = inf + # Find the minimum-weighted (u, v) Δ-residual edge. + for k, e in es.items(): + if e["capacity"] - e["flow"] >= delta: + w = e["weight"] + if w < wmin: + wmin = w + kmin = k + emin = e + if wmin == inf: + continue + # Update the distance label of v. + d_v = d_u + wmin - p_u + R_nodes[v]["potential"] + if h_insert(v, d_v): + pred[v] = (u, kmin, emin) + if t is not None: + # Augment Δ units of flow from s to t. + while u != s: + v = u + u, k, e = pred[v] + e["flow"] += delta + R_succ[v][u][(k[0], not k[1])]["flow"] -= delta + # Account node excess and deficit. + R_nodes[s]["excess"] -= delta + R_nodes[t]["excess"] += delta + if R_nodes[s]["excess"] < delta: + S_remove(s) + if R_nodes[t]["excess"] > -delta: + T_remove(t) + # Update node potentials. + d_t = d[t] + for u, d_u in d.items(): + R_nodes[u]["potential"] -= d_u - d_t + else: + # Path not found. + S_remove(s) + delta //= 2 + + if any(R.nodes[u]["excess"] != 0 for u in R): + raise nx.NetworkXUnfeasible("No flow satisfying all demands.") + + # Calculate the flow cost. + for u in R: + for v, es in R_succ[u].items(): + for e in es.values(): + flow = e["flow"] + if flow > 0: + flow_cost += flow * e["weight"] + + return flow_cost, _build_flow_dict(G, R, capacity, weight) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/dinitz_alg.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/dinitz_alg.py new file mode 100644 index 0000000000000000000000000000000000000000..f369642af2968094184741132a843f5dde81e428 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/dinitz_alg.py @@ -0,0 +1,238 @@ +""" +Dinitz' algorithm for maximum flow problems. +""" + +from collections import deque + +import networkx as nx +from networkx.algorithms.flow.utils import build_residual_network +from networkx.utils import pairwise + +__all__ = ["dinitz"] + + +@nx._dispatchable(edge_attrs={"capacity": float("inf")}, returns_graph=True) +def dinitz(G, s, t, capacity="capacity", residual=None, value_only=False, cutoff=None): + """Find a maximum single-commodity flow using Dinitz' algorithm. + + This function returns the residual network resulting after computing + the maximum flow. See below for details about the conventions + NetworkX uses for defining residual networks. + + This algorithm has a running time of $O(n^2 m)$ for $n$ nodes and $m$ + edges [1]_. + + + Parameters + ---------- + G : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + s : node + Source node for the flow. + + t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + residual : NetworkX graph + Residual network on which the algorithm is to be executed. If None, a + new residual network is created. Default value: None. + + value_only : bool + If True compute only the value of the maximum flow. This parameter + will be ignored by this algorithm because it is not applicable. + + cutoff : integer, float + If specified, the algorithm will terminate when the flow value reaches + or exceeds the cutoff. In this case, it may be unable to immediately + determine a minimum cut. Default value: None. + + Returns + ------- + R : NetworkX DiGraph + Residual network after computing the maximum flow. + + Raises + ------ + NetworkXError + The algorithm does not support MultiGraph and MultiDiGraph. If + the input graph is an instance of one of these two classes, a + NetworkXError is raised. + + NetworkXUnbounded + If the graph has a path of infinite capacity, the value of a + feasible flow on the graph is unbounded above and the function + raises a NetworkXUnbounded. + + See also + -------- + :meth:`maximum_flow` + :meth:`minimum_cut` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. If :samp:`cutoff` is not + specified, reachability to :samp:`t` using only edges :samp:`(u, v)` such + that :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Examples + -------- + >>> from networkx.algorithms.flow import dinitz + + The functions that implement flow algorithms and output a residual + network, such as this one, are not imported to the base NetworkX + namespace, so you have to explicitly import them from the flow package. + + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + >>> R = dinitz(G, "x", "y") + >>> flow_value = nx.maximum_flow_value(G, "x", "y") + >>> flow_value + 3.0 + >>> flow_value == R.graph["flow_value"] + True + + References + ---------- + .. [1] Dinitz' Algorithm: The Original Version and Even's Version. + 2006. Yefim Dinitz. In Theoretical Computer Science. Lecture + Notes in Computer Science. Volume 3895. pp 218-240. + https://doi.org/10.1007/11685654_10 + + """ + R = dinitz_impl(G, s, t, capacity, residual, cutoff) + R.graph["algorithm"] = "dinitz" + nx._clear_cache(R) + return R + + +def dinitz_impl(G, s, t, capacity, residual, cutoff): + if s not in G: + raise nx.NetworkXError(f"node {str(s)} not in graph") + if t not in G: + raise nx.NetworkXError(f"node {str(t)} not in graph") + if s == t: + raise nx.NetworkXError("source and sink are the same node") + + if residual is None: + R = build_residual_network(G, capacity) + else: + R = residual + + # Initialize/reset the residual network. + for u in R: + for e in R[u].values(): + e["flow"] = 0 + + # Use an arbitrary high value as infinite. It is computed + # when building the residual network. + INF = R.graph["inf"] + + if cutoff is None: + cutoff = INF + + R_succ = R.succ + R_pred = R.pred + + def breath_first_search(): + parents = {} + vertex_dist = {s: 0} + queue = deque([(s, 0)]) + # Record all the potential edges of shortest augmenting paths + while queue: + if t in parents: + break + u, dist = queue.popleft() + for v, attr in R_succ[u].items(): + if attr["capacity"] - attr["flow"] > 0: + if v in parents: + if vertex_dist[v] == dist + 1: + parents[v].append(u) + else: + parents[v] = deque([u]) + vertex_dist[v] = dist + 1 + queue.append((v, dist + 1)) + return parents + + def depth_first_search(parents): + # DFS to find all the shortest augmenting paths + """Build a path using DFS starting from the sink""" + total_flow = 0 + u = t + # path also functions as a stack + path = [u] + # The loop ends with no augmenting path left in the layered graph + while True: + if len(parents[u]) > 0: + v = parents[u][0] + path.append(v) + else: + path.pop() + if len(path) == 0: + break + v = path[-1] + parents[v].popleft() + # Augment the flow along the path found + if v == s: + flow = INF + for u, v in pairwise(path): + flow = min(flow, R_pred[u][v]["capacity"] - R_pred[u][v]["flow"]) + for u, v in pairwise(reversed(path)): + R_pred[v][u]["flow"] += flow + R_pred[u][v]["flow"] -= flow + # Find the proper node to continue the search + if R_pred[v][u]["capacity"] - R_pred[v][u]["flow"] == 0: + parents[v].popleft() + while path[-1] != v: + path.pop() + total_flow += flow + v = path[-1] + u = v + return total_flow + + flow_value = 0 + while flow_value < cutoff: + parents = breath_first_search() + if t not in parents: + break + this_flow = depth_first_search(parents) + if this_flow * 2 > INF: + raise nx.NetworkXUnbounded("Infinite capacity path, flow unbounded above.") + flow_value += this_flow + + R.graph["flow_value"] = flow_value + return R diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/edmondskarp.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/edmondskarp.py new file mode 100644 index 0000000000000000000000000000000000000000..50063268355ccc2e2ecbdf7f1a6704e7404475ec --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/edmondskarp.py @@ -0,0 +1,241 @@ +""" +Edmonds-Karp algorithm for maximum flow problems. +""" + +import networkx as nx +from networkx.algorithms.flow.utils import build_residual_network + +__all__ = ["edmonds_karp"] + + +def edmonds_karp_core(R, s, t, cutoff): + """Implementation of the Edmonds-Karp algorithm.""" + R_nodes = R.nodes + R_pred = R.pred + R_succ = R.succ + + inf = R.graph["inf"] + + def augment(path): + """Augment flow along a path from s to t.""" + # Determine the path residual capacity. + flow = inf + it = iter(path) + u = next(it) + for v in it: + attr = R_succ[u][v] + flow = min(flow, attr["capacity"] - attr["flow"]) + u = v + if flow * 2 > inf: + raise nx.NetworkXUnbounded("Infinite capacity path, flow unbounded above.") + # Augment flow along the path. + it = iter(path) + u = next(it) + for v in it: + R_succ[u][v]["flow"] += flow + R_succ[v][u]["flow"] -= flow + u = v + return flow + + def bidirectional_bfs(): + """Bidirectional breadth-first search for an augmenting path.""" + pred = {s: None} + q_s = [s] + succ = {t: None} + q_t = [t] + while True: + q = [] + if len(q_s) <= len(q_t): + for u in q_s: + for v, attr in R_succ[u].items(): + if v not in pred and attr["flow"] < attr["capacity"]: + pred[v] = u + if v in succ: + return v, pred, succ + q.append(v) + if not q: + return None, None, None + q_s = q + else: + for u in q_t: + for v, attr in R_pred[u].items(): + if v not in succ and attr["flow"] < attr["capacity"]: + succ[v] = u + if v in pred: + return v, pred, succ + q.append(v) + if not q: + return None, None, None + q_t = q + + # Look for shortest augmenting paths using breadth-first search. + flow_value = 0 + while flow_value < cutoff: + v, pred, succ = bidirectional_bfs() + if pred is None: + break + path = [v] + # Trace a path from s to v. + u = v + while u != s: + u = pred[u] + path.append(u) + path.reverse() + # Trace a path from v to t. + u = v + while u != t: + u = succ[u] + path.append(u) + flow_value += augment(path) + + return flow_value + + +def edmonds_karp_impl(G, s, t, capacity, residual, cutoff): + """Implementation of the Edmonds-Karp algorithm.""" + if s not in G: + raise nx.NetworkXError(f"node {str(s)} not in graph") + if t not in G: + raise nx.NetworkXError(f"node {str(t)} not in graph") + if s == t: + raise nx.NetworkXError("source and sink are the same node") + + if residual is None: + R = build_residual_network(G, capacity) + else: + R = residual + + # Initialize/reset the residual network. + for u in R: + for e in R[u].values(): + e["flow"] = 0 + + if cutoff is None: + cutoff = float("inf") + R.graph["flow_value"] = edmonds_karp_core(R, s, t, cutoff) + + return R + + +@nx._dispatchable(edge_attrs={"capacity": float("inf")}, returns_graph=True) +def edmonds_karp( + G, s, t, capacity="capacity", residual=None, value_only=False, cutoff=None +): + """Find a maximum single-commodity flow using the Edmonds-Karp algorithm. + + This function returns the residual network resulting after computing + the maximum flow. See below for details about the conventions + NetworkX uses for defining residual networks. + + This algorithm has a running time of $O(n m^2)$ for $n$ nodes and $m$ + edges. + + + Parameters + ---------- + G : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + s : node + Source node for the flow. + + t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + residual : NetworkX graph + Residual network on which the algorithm is to be executed. If None, a + new residual network is created. Default value: None. + + value_only : bool + If True compute only the value of the maximum flow. This parameter + will be ignored by this algorithm because it is not applicable. + + cutoff : integer, float + If specified, the algorithm will terminate when the flow value reaches + or exceeds the cutoff. In this case, it may be unable to immediately + determine a minimum cut. Default value: None. + + Returns + ------- + R : NetworkX DiGraph + Residual network after computing the maximum flow. + + Raises + ------ + NetworkXError + The algorithm does not support MultiGraph and MultiDiGraph. If + the input graph is an instance of one of these two classes, a + NetworkXError is raised. + + NetworkXUnbounded + If the graph has a path of infinite capacity, the value of a + feasible flow on the graph is unbounded above and the function + raises a NetworkXUnbounded. + + See also + -------- + :meth:`maximum_flow` + :meth:`minimum_cut` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. If :samp:`cutoff` is not + specified, reachability to :samp:`t` using only edges :samp:`(u, v)` such + that :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Examples + -------- + >>> from networkx.algorithms.flow import edmonds_karp + + The functions that implement flow algorithms and output a residual + network, such as this one, are not imported to the base NetworkX + namespace, so you have to explicitly import them from the flow package. + + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + >>> R = edmonds_karp(G, "x", "y") + >>> flow_value = nx.maximum_flow_value(G, "x", "y") + >>> flow_value + 3.0 + >>> flow_value == R.graph["flow_value"] + True + + """ + R = edmonds_karp_impl(G, s, t, capacity, residual, cutoff) + R.graph["algorithm"] = "edmonds_karp" + nx._clear_cache(R) + return R diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/gomory_hu.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/gomory_hu.py new file mode 100644 index 0000000000000000000000000000000000000000..69913da904547b3a9fe682467b69e696e9c8e0dc --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/gomory_hu.py @@ -0,0 +1,178 @@ +""" +Gomory-Hu tree of undirected Graphs. +""" + +import networkx as nx +from networkx.utils import not_implemented_for + +from .edmondskarp import edmonds_karp +from .utils import build_residual_network + +default_flow_func = edmonds_karp + +__all__ = ["gomory_hu_tree"] + + +@not_implemented_for("directed") +@nx._dispatchable(edge_attrs={"capacity": float("inf")}, returns_graph=True) +def gomory_hu_tree(G, capacity="capacity", flow_func=None): + r"""Returns the Gomory-Hu tree of an undirected graph G. + + A Gomory-Hu tree of an undirected graph with capacities is a + weighted tree that represents the minimum s-t cuts for all s-t + pairs in the graph. + + It only requires `n-1` minimum cut computations instead of the + obvious `n(n-1)/2`. The tree represents all s-t cuts as the + minimum cut value among any pair of nodes is the minimum edge + weight in the shortest path between the two nodes in the + Gomory-Hu tree. + + The Gomory-Hu tree also has the property that removing the + edge with the minimum weight in the shortest path between + any two nodes leaves two connected components that form + a partition of the nodes in G that defines the minimum s-t + cut. + + See Examples section below for details. + + Parameters + ---------- + G : NetworkX graph + Undirected graph + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + flow_func : function + Function to perform the underlying flow computations. Default value + :func:`edmonds_karp`. This function performs better in sparse graphs + with right tailed degree distributions. + :func:`shortest_augmenting_path` will perform better in denser + graphs. + + Returns + ------- + Tree : NetworkX graph + A NetworkX graph representing the Gomory-Hu tree of the input graph. + + Raises + ------ + NetworkXNotImplemented + Raised if the input graph is directed. + + NetworkXError + Raised if the input graph is an empty Graph. + + Examples + -------- + >>> G = nx.karate_club_graph() + >>> nx.set_edge_attributes(G, 1, "capacity") + >>> T = nx.gomory_hu_tree(G) + >>> # The value of the minimum cut between any pair + ... # of nodes in G is the minimum edge weight in the + ... # shortest path between the two nodes in the + ... # Gomory-Hu tree. + ... def minimum_edge_weight_in_shortest_path(T, u, v): + ... path = nx.shortest_path(T, u, v, weight="weight") + ... return min((T[u][v]["weight"], (u, v)) for (u, v) in zip(path, path[1:])) + >>> u, v = 0, 33 + >>> cut_value, edge = minimum_edge_weight_in_shortest_path(T, u, v) + >>> cut_value + 10 + >>> nx.minimum_cut_value(G, u, v) + 10 + >>> # The Gomory-Hu tree also has the property that removing the + ... # edge with the minimum weight in the shortest path between + ... # any two nodes leaves two connected components that form + ... # a partition of the nodes in G that defines the minimum s-t + ... # cut. + ... cut_value, edge = minimum_edge_weight_in_shortest_path(T, u, v) + >>> T.remove_edge(*edge) + >>> U, V = list(nx.connected_components(T)) + >>> # Thus U and V form a partition that defines a minimum cut + ... # between u and v in G. You can compute the edge cut set, + ... # that is, the set of edges that if removed from G will + ... # disconnect u from v in G, with this information: + ... cutset = set() + >>> for x, nbrs in ((n, G[n]) for n in U): + ... cutset.update((x, y) for y in nbrs if y in V) + >>> # Because we have set the capacities of all edges to 1 + ... # the cutset contains ten edges + ... len(cutset) + 10 + >>> # You can use any maximum flow algorithm for the underlying + ... # flow computations using the argument flow_func + ... from networkx.algorithms import flow + >>> T = nx.gomory_hu_tree(G, flow_func=flow.boykov_kolmogorov) + >>> cut_value, edge = minimum_edge_weight_in_shortest_path(T, u, v) + >>> cut_value + 10 + >>> nx.minimum_cut_value(G, u, v, flow_func=flow.boykov_kolmogorov) + 10 + + Notes + ----- + This implementation is based on Gusfield approach [1]_ to compute + Gomory-Hu trees, which does not require node contractions and has + the same computational complexity than the original method. + + See also + -------- + :func:`minimum_cut` + :func:`maximum_flow` + + References + ---------- + .. [1] Gusfield D: Very simple methods for all pairs network flow analysis. + SIAM J Comput 19(1):143-155, 1990. + + """ + if flow_func is None: + flow_func = default_flow_func + + if len(G) == 0: # empty graph + msg = "Empty Graph does not have a Gomory-Hu tree representation" + raise nx.NetworkXError(msg) + + # Start the tree as a star graph with an arbitrary node at the center + tree = {} + labels = {} + iter_nodes = iter(G) + root = next(iter_nodes) + for n in iter_nodes: + tree[n] = root + + # Reuse residual network + R = build_residual_network(G, capacity) + + # For all the leaves in the star graph tree (that is n-1 nodes). + for source in tree: + # Find neighbor in the tree + target = tree[source] + # compute minimum cut + cut_value, partition = nx.minimum_cut( + G, source, target, capacity=capacity, flow_func=flow_func, residual=R + ) + labels[(source, target)] = cut_value + # Update the tree + # Source will always be in partition[0] and target in partition[1] + for node in partition[0]: + if node != source and node in tree and tree[node] == target: + tree[node] = source + labels[node, source] = labels.get((node, target), cut_value) + # + if target != root and tree[target] in partition[0]: + labels[source, tree[target]] = labels[target, tree[target]] + labels[target, source] = cut_value + tree[source] = tree[target] + tree[target] = source + + # Build the tree + T = nx.Graph() + T.add_nodes_from(G) + T.add_weighted_edges_from(((u, v, labels[u, v]) for u, v in tree.items())) + return T diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/maxflow.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/maxflow.py new file mode 100644 index 0000000000000000000000000000000000000000..7993d87ba9ad8c3f3aa0639f82590f4c16f5f4b7 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/maxflow.py @@ -0,0 +1,607 @@ +""" +Maximum flow (and minimum cut) algorithms on capacitated graphs. +""" + +import networkx as nx + +from .boykovkolmogorov import boykov_kolmogorov +from .dinitz_alg import dinitz +from .edmondskarp import edmonds_karp +from .preflowpush import preflow_push +from .shortestaugmentingpath import shortest_augmenting_path +from .utils import build_flow_dict + +# Define the default flow function for computing maximum flow. +default_flow_func = preflow_push + +__all__ = ["maximum_flow", "maximum_flow_value", "minimum_cut", "minimum_cut_value"] + + +@nx._dispatchable(graphs="flowG", edge_attrs={"capacity": float("inf")}) +def maximum_flow(flowG, _s, _t, capacity="capacity", flow_func=None, **kwargs): + """Find a maximum single-commodity flow. + + Parameters + ---------- + flowG : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + _s : node + Source node for the flow. + + _t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + flow_func : function + A function for computing the maximum flow among a pair of nodes + in a capacitated graph. The function has to accept at least three + parameters: a Graph or Digraph, a source node, and a target node. + And return a residual network that follows NetworkX conventions + (see Notes). If flow_func is None, the default maximum + flow function (:meth:`preflow_push`) is used. See below for + alternative algorithms. The choice of the default function may change + from version to version and should not be relied on. Default value: + None. + + kwargs : Any other keyword parameter is passed to the function that + computes the maximum flow. + + Returns + ------- + flow_value : integer, float + Value of the maximum flow, i.e., net outflow from the source. + + flow_dict : dict + A dictionary containing the value of the flow that went through + each edge. + + Raises + ------ + NetworkXError + The algorithm does not support MultiGraph and MultiDiGraph. If + the input graph is an instance of one of these two classes, a + NetworkXError is raised. + + NetworkXUnbounded + If the graph has a path of infinite capacity, the value of a + feasible flow on the graph is unbounded above and the function + raises a NetworkXUnbounded. + + See also + -------- + :meth:`maximum_flow_value` + :meth:`minimum_cut` + :meth:`minimum_cut_value` + :meth:`edmonds_karp` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The function used in the flow_func parameter has to return a residual + network that follows NetworkX conventions: + + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. Reachability to :samp:`t` using + only edges :samp:`(u, v)` such that + :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Specific algorithms may store extra data in :samp:`R`. + + The function should supports an optional boolean parameter value_only. When + True, it can optionally terminate the algorithm as soon as the maximum flow + value and the minimum cut can be determined. + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + + maximum_flow returns both the value of the maximum flow and a + dictionary with all flows. + + >>> flow_value, flow_dict = nx.maximum_flow(G, "x", "y") + >>> flow_value + 3.0 + >>> print(flow_dict["x"]["b"]) + 1.0 + + You can also use alternative algorithms for computing the + maximum flow by using the flow_func parameter. + + >>> from networkx.algorithms.flow import shortest_augmenting_path + >>> flow_value == nx.maximum_flow(G, "x", "y", flow_func=shortest_augmenting_path)[ + ... 0 + ... ] + True + + """ + if flow_func is None: + if kwargs: + raise nx.NetworkXError( + "You have to explicitly set a flow_func if" + " you need to pass parameters via kwargs." + ) + flow_func = default_flow_func + + if not callable(flow_func): + raise nx.NetworkXError("flow_func has to be callable.") + + R = flow_func(flowG, _s, _t, capacity=capacity, value_only=False, **kwargs) + flow_dict = build_flow_dict(flowG, R) + + return (R.graph["flow_value"], flow_dict) + + +@nx._dispatchable(graphs="flowG", edge_attrs={"capacity": float("inf")}) +def maximum_flow_value(flowG, _s, _t, capacity="capacity", flow_func=None, **kwargs): + """Find the value of maximum single-commodity flow. + + Parameters + ---------- + flowG : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + _s : node + Source node for the flow. + + _t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + flow_func : function + A function for computing the maximum flow among a pair of nodes + in a capacitated graph. The function has to accept at least three + parameters: a Graph or Digraph, a source node, and a target node. + And return a residual network that follows NetworkX conventions + (see Notes). If flow_func is None, the default maximum + flow function (:meth:`preflow_push`) is used. See below for + alternative algorithms. The choice of the default function may change + from version to version and should not be relied on. Default value: + None. + + kwargs : Any other keyword parameter is passed to the function that + computes the maximum flow. + + Returns + ------- + flow_value : integer, float + Value of the maximum flow, i.e., net outflow from the source. + + Raises + ------ + NetworkXError + The algorithm does not support MultiGraph and MultiDiGraph. If + the input graph is an instance of one of these two classes, a + NetworkXError is raised. + + NetworkXUnbounded + If the graph has a path of infinite capacity, the value of a + feasible flow on the graph is unbounded above and the function + raises a NetworkXUnbounded. + + See also + -------- + :meth:`maximum_flow` + :meth:`minimum_cut` + :meth:`minimum_cut_value` + :meth:`edmonds_karp` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The function used in the flow_func parameter has to return a residual + network that follows NetworkX conventions: + + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. Reachability to :samp:`t` using + only edges :samp:`(u, v)` such that + :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Specific algorithms may store extra data in :samp:`R`. + + The function should supports an optional boolean parameter value_only. When + True, it can optionally terminate the algorithm as soon as the maximum flow + value and the minimum cut can be determined. + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + + maximum_flow_value computes only the value of the + maximum flow: + + >>> flow_value = nx.maximum_flow_value(G, "x", "y") + >>> flow_value + 3.0 + + You can also use alternative algorithms for computing the + maximum flow by using the flow_func parameter. + + >>> from networkx.algorithms.flow import shortest_augmenting_path + >>> flow_value == nx.maximum_flow_value( + ... G, "x", "y", flow_func=shortest_augmenting_path + ... ) + True + + """ + if flow_func is None: + if kwargs: + raise nx.NetworkXError( + "You have to explicitly set a flow_func if" + " you need to pass parameters via kwargs." + ) + flow_func = default_flow_func + + if not callable(flow_func): + raise nx.NetworkXError("flow_func has to be callable.") + + R = flow_func(flowG, _s, _t, capacity=capacity, value_only=True, **kwargs) + + return R.graph["flow_value"] + + +@nx._dispatchable(graphs="flowG", edge_attrs={"capacity": float("inf")}) +def minimum_cut(flowG, _s, _t, capacity="capacity", flow_func=None, **kwargs): + """Compute the value and the node partition of a minimum (s, t)-cut. + + Use the max-flow min-cut theorem, i.e., the capacity of a minimum + capacity cut is equal to the flow value of a maximum flow. + + Parameters + ---------- + flowG : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + _s : node + Source node for the flow. + + _t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + flow_func : function + A function for computing the maximum flow among a pair of nodes + in a capacitated graph. The function has to accept at least three + parameters: a Graph or Digraph, a source node, and a target node. + And return a residual network that follows NetworkX conventions + (see Notes). If flow_func is None, the default maximum + flow function (:meth:`preflow_push`) is used. See below for + alternative algorithms. The choice of the default function may change + from version to version and should not be relied on. Default value: + None. + + kwargs : Any other keyword parameter is passed to the function that + computes the maximum flow. + + Returns + ------- + cut_value : integer, float + Value of the minimum cut. + + partition : pair of node sets + A partitioning of the nodes that defines a minimum cut. + + Raises + ------ + NetworkXUnbounded + If the graph has a path of infinite capacity, all cuts have + infinite capacity and the function raises a NetworkXError. + + See also + -------- + :meth:`maximum_flow` + :meth:`maximum_flow_value` + :meth:`minimum_cut_value` + :meth:`edmonds_karp` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The function used in the flow_func parameter has to return a residual + network that follows NetworkX conventions: + + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. Reachability to :samp:`t` using + only edges :samp:`(u, v)` such that + :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Specific algorithms may store extra data in :samp:`R`. + + The function should supports an optional boolean parameter value_only. When + True, it can optionally terminate the algorithm as soon as the maximum flow + value and the minimum cut can be determined. + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + + minimum_cut computes both the value of the + minimum cut and the node partition: + + >>> cut_value, partition = nx.minimum_cut(G, "x", "y") + >>> reachable, non_reachable = partition + + 'partition' here is a tuple with the two sets of nodes that define + the minimum cut. You can compute the cut set of edges that induce + the minimum cut as follows: + + >>> cutset = set() + >>> for u, nbrs in ((n, G[n]) for n in reachable): + ... cutset.update((u, v) for v in nbrs if v in non_reachable) + >>> print(sorted(cutset)) + [('c', 'y'), ('x', 'b')] + >>> cut_value == sum(G.edges[u, v]["capacity"] for (u, v) in cutset) + True + + You can also use alternative algorithms for computing the + minimum cut by using the flow_func parameter. + + >>> from networkx.algorithms.flow import shortest_augmenting_path + >>> cut_value == nx.minimum_cut(G, "x", "y", flow_func=shortest_augmenting_path)[0] + True + + """ + if flow_func is None: + if kwargs: + raise nx.NetworkXError( + "You have to explicitly set a flow_func if" + " you need to pass parameters via kwargs." + ) + flow_func = default_flow_func + + if not callable(flow_func): + raise nx.NetworkXError("flow_func has to be callable.") + + if kwargs.get("cutoff") is not None and flow_func is preflow_push: + raise nx.NetworkXError("cutoff should not be specified.") + + R = flow_func(flowG, _s, _t, capacity=capacity, value_only=True, **kwargs) + # Remove saturated edges from the residual network + cutset = [(u, v, d) for u, v, d in R.edges(data=True) if d["flow"] == d["capacity"]] + R.remove_edges_from(cutset) + + # Then, reachable and non reachable nodes from source in the + # residual network form the node partition that defines + # the minimum cut. + non_reachable = set(dict(nx.shortest_path_length(R, target=_t))) + partition = (set(flowG) - non_reachable, non_reachable) + # Finally add again cutset edges to the residual network to make + # sure that it is reusable. + R.add_edges_from(cutset) + return (R.graph["flow_value"], partition) + + +@nx._dispatchable(graphs="flowG", edge_attrs={"capacity": float("inf")}) +def minimum_cut_value(flowG, _s, _t, capacity="capacity", flow_func=None, **kwargs): + """Compute the value of a minimum (s, t)-cut. + + Use the max-flow min-cut theorem, i.e., the capacity of a minimum + capacity cut is equal to the flow value of a maximum flow. + + Parameters + ---------- + flowG : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + _s : node + Source node for the flow. + + _t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + flow_func : function + A function for computing the maximum flow among a pair of nodes + in a capacitated graph. The function has to accept at least three + parameters: a Graph or Digraph, a source node, and a target node. + And return a residual network that follows NetworkX conventions + (see Notes). If flow_func is None, the default maximum + flow function (:meth:`preflow_push`) is used. See below for + alternative algorithms. The choice of the default function may change + from version to version and should not be relied on. Default value: + None. + + kwargs : Any other keyword parameter is passed to the function that + computes the maximum flow. + + Returns + ------- + cut_value : integer, float + Value of the minimum cut. + + Raises + ------ + NetworkXUnbounded + If the graph has a path of infinite capacity, all cuts have + infinite capacity and the function raises a NetworkXError. + + See also + -------- + :meth:`maximum_flow` + :meth:`maximum_flow_value` + :meth:`minimum_cut` + :meth:`edmonds_karp` + :meth:`preflow_push` + :meth:`shortest_augmenting_path` + + Notes + ----- + The function used in the flow_func parameter has to return a residual + network that follows NetworkX conventions: + + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. Reachability to :samp:`t` using + only edges :samp:`(u, v)` such that + :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Specific algorithms may store extra data in :samp:`R`. + + The function should supports an optional boolean parameter value_only. When + True, it can optionally terminate the algorithm as soon as the maximum flow + value and the minimum cut can be determined. + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + + minimum_cut_value computes only the value of the + minimum cut: + + >>> cut_value = nx.minimum_cut_value(G, "x", "y") + >>> cut_value + 3.0 + + You can also use alternative algorithms for computing the + minimum cut by using the flow_func parameter. + + >>> from networkx.algorithms.flow import shortest_augmenting_path + >>> cut_value == nx.minimum_cut_value( + ... G, "x", "y", flow_func=shortest_augmenting_path + ... ) + True + + """ + if flow_func is None: + if kwargs: + raise nx.NetworkXError( + "You have to explicitly set a flow_func if" + " you need to pass parameters via kwargs." + ) + flow_func = default_flow_func + + if not callable(flow_func): + raise nx.NetworkXError("flow_func has to be callable.") + + if kwargs.get("cutoff") is not None and flow_func is preflow_push: + raise nx.NetworkXError("cutoff should not be specified.") + + R = flow_func(flowG, _s, _t, capacity=capacity, value_only=True, **kwargs) + + return R.graph["flow_value"] diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/mincost.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/mincost.py new file mode 100644 index 0000000000000000000000000000000000000000..2f9390d7a1c1e454ed7c2f8793d591b338115107 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/mincost.py @@ -0,0 +1,356 @@ +""" +Minimum cost flow algorithms on directed connected graphs. +""" + +__all__ = ["min_cost_flow_cost", "min_cost_flow", "cost_of_flow", "max_flow_min_cost"] + +import networkx as nx + + +@nx._dispatchable( + node_attrs="demand", edge_attrs={"capacity": float("inf"), "weight": 0} +) +def min_cost_flow_cost(G, demand="demand", capacity="capacity", weight="weight"): + r"""Find the cost of a minimum cost flow satisfying all demands in digraph G. + + G is a digraph with edge costs and capacities and in which nodes + have demand, i.e., they want to send or receive some amount of + flow. A negative demand means that the node wants to send flow, a + positive demand means that the node want to receive flow. A flow on + the digraph G satisfies all demand if the net flow into each node + is equal to the demand of that node. + + Parameters + ---------- + G : NetworkX graph + DiGraph on which a minimum cost flow satisfying all demands is + to be found. + + demand : string + Nodes of the graph G are expected to have an attribute demand + that indicates how much flow a node wants to send (negative + demand) or receive (positive demand). Note that the sum of the + demands should be 0 otherwise the problem in not feasible. If + this attribute is not present, a node is considered to have 0 + demand. Default value: 'demand'. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + weight : string + Edges of the graph G are expected to have an attribute weight + that indicates the cost incurred by sending one unit of flow on + that edge. If not present, the weight is considered to be 0. + Default value: 'weight'. + + Returns + ------- + flowCost : integer, float + Cost of a minimum cost flow satisfying all demands. + + Raises + ------ + NetworkXError + This exception is raised if the input graph is not directed or + not connected. + + NetworkXUnfeasible + This exception is raised in the following situations: + + * The sum of the demands is not zero. Then, there is no + flow satisfying all demands. + * There is no flow satisfying all demand. + + NetworkXUnbounded + This exception is raised if the digraph G has a cycle of + negative cost and infinite capacity. Then, the cost of a flow + satisfying all demands is unbounded below. + + See also + -------- + cost_of_flow, max_flow_min_cost, min_cost_flow, network_simplex + + Notes + ----- + This algorithm is not guaranteed to work if edge weights or demands + are floating point numbers (overflows and roundoff errors can + cause problems). As a workaround you can use integer numbers by + multiplying the relevant edge attributes by a convenient + constant factor (eg 100). + + Examples + -------- + A simple example of a min cost flow problem. + + >>> G = nx.DiGraph() + >>> G.add_node("a", demand=-5) + >>> G.add_node("d", demand=5) + >>> G.add_edge("a", "b", weight=3, capacity=4) + >>> G.add_edge("a", "c", weight=6, capacity=10) + >>> G.add_edge("b", "d", weight=1, capacity=9) + >>> G.add_edge("c", "d", weight=2, capacity=5) + >>> flowCost = nx.min_cost_flow_cost(G) + >>> flowCost + 24 + """ + return nx.network_simplex(G, demand=demand, capacity=capacity, weight=weight)[0] + + +@nx._dispatchable( + node_attrs="demand", edge_attrs={"capacity": float("inf"), "weight": 0} +) +def min_cost_flow(G, demand="demand", capacity="capacity", weight="weight"): + r"""Returns a minimum cost flow satisfying all demands in digraph G. + + G is a digraph with edge costs and capacities and in which nodes + have demand, i.e., they want to send or receive some amount of + flow. A negative demand means that the node wants to send flow, a + positive demand means that the node want to receive flow. A flow on + the digraph G satisfies all demand if the net flow into each node + is equal to the demand of that node. + + Parameters + ---------- + G : NetworkX graph + DiGraph on which a minimum cost flow satisfying all demands is + to be found. + + demand : string + Nodes of the graph G are expected to have an attribute demand + that indicates how much flow a node wants to send (negative + demand) or receive (positive demand). Note that the sum of the + demands should be 0 otherwise the problem in not feasible. If + this attribute is not present, a node is considered to have 0 + demand. Default value: 'demand'. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + weight : string + Edges of the graph G are expected to have an attribute weight + that indicates the cost incurred by sending one unit of flow on + that edge. If not present, the weight is considered to be 0. + Default value: 'weight'. + + Returns + ------- + flowDict : dictionary + Dictionary of dictionaries keyed by nodes such that + flowDict[u][v] is the flow edge (u, v). + + Raises + ------ + NetworkXError + This exception is raised if the input graph is not directed or + not connected. + + NetworkXUnfeasible + This exception is raised in the following situations: + + * The sum of the demands is not zero. Then, there is no + flow satisfying all demands. + * There is no flow satisfying all demand. + + NetworkXUnbounded + This exception is raised if the digraph G has a cycle of + negative cost and infinite capacity. Then, the cost of a flow + satisfying all demands is unbounded below. + + See also + -------- + cost_of_flow, max_flow_min_cost, min_cost_flow_cost, network_simplex + + Notes + ----- + This algorithm is not guaranteed to work if edge weights or demands + are floating point numbers (overflows and roundoff errors can + cause problems). As a workaround you can use integer numbers by + multiplying the relevant edge attributes by a convenient + constant factor (eg 100). + + Examples + -------- + A simple example of a min cost flow problem. + + >>> G = nx.DiGraph() + >>> G.add_node("a", demand=-5) + >>> G.add_node("d", demand=5) + >>> G.add_edge("a", "b", weight=3, capacity=4) + >>> G.add_edge("a", "c", weight=6, capacity=10) + >>> G.add_edge("b", "d", weight=1, capacity=9) + >>> G.add_edge("c", "d", weight=2, capacity=5) + >>> flowDict = nx.min_cost_flow(G) + >>> flowDict + {'a': {'b': 4, 'c': 1}, 'd': {}, 'b': {'d': 4}, 'c': {'d': 1}} + """ + return nx.network_simplex(G, demand=demand, capacity=capacity, weight=weight)[1] + + +@nx._dispatchable(edge_attrs={"weight": 0}) +def cost_of_flow(G, flowDict, weight="weight"): + """Compute the cost of the flow given by flowDict on graph G. + + Note that this function does not check for the validity of the + flow flowDict. This function will fail if the graph G and the + flow don't have the same edge set. + + Parameters + ---------- + G : NetworkX graph + DiGraph on which a minimum cost flow satisfying all demands is + to be found. + + weight : string + Edges of the graph G are expected to have an attribute weight + that indicates the cost incurred by sending one unit of flow on + that edge. If not present, the weight is considered to be 0. + Default value: 'weight'. + + flowDict : dictionary + Dictionary of dictionaries keyed by nodes such that + flowDict[u][v] is the flow edge (u, v). + + Returns + ------- + cost : Integer, float + The total cost of the flow. This is given by the sum over all + edges of the product of the edge's flow and the edge's weight. + + See also + -------- + max_flow_min_cost, min_cost_flow, min_cost_flow_cost, network_simplex + + Notes + ----- + This algorithm is not guaranteed to work if edge weights or demands + are floating point numbers (overflows and roundoff errors can + cause problems). As a workaround you can use integer numbers by + multiplying the relevant edge attributes by a convenient + constant factor (eg 100). + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_node("a", demand=-5) + >>> G.add_node("d", demand=5) + >>> G.add_edge("a", "b", weight=3, capacity=4) + >>> G.add_edge("a", "c", weight=6, capacity=10) + >>> G.add_edge("b", "d", weight=1, capacity=9) + >>> G.add_edge("c", "d", weight=2, capacity=5) + >>> flowDict = nx.min_cost_flow(G) + >>> flowDict + {'a': {'b': 4, 'c': 1}, 'd': {}, 'b': {'d': 4}, 'c': {'d': 1}} + >>> nx.cost_of_flow(G, flowDict) + 24 + """ + return sum((flowDict[u][v] * d.get(weight, 0) for u, v, d in G.edges(data=True))) + + +@nx._dispatchable(edge_attrs={"capacity": float("inf"), "weight": 0}) +def max_flow_min_cost(G, s, t, capacity="capacity", weight="weight"): + """Returns a maximum (s, t)-flow of minimum cost. + + G is a digraph with edge costs and capacities. There is a source + node s and a sink node t. This function finds a maximum flow from + s to t whose total cost is minimized. + + Parameters + ---------- + G : NetworkX graph + DiGraph on which a minimum cost flow satisfying all demands is + to be found. + + s: node label + Source of the flow. + + t: node label + Destination of the flow. + + capacity: string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + weight: string + Edges of the graph G are expected to have an attribute weight + that indicates the cost incurred by sending one unit of flow on + that edge. If not present, the weight is considered to be 0. + Default value: 'weight'. + + Returns + ------- + flowDict: dictionary + Dictionary of dictionaries keyed by nodes such that + flowDict[u][v] is the flow edge (u, v). + + Raises + ------ + NetworkXError + This exception is raised if the input graph is not directed or + not connected. + + NetworkXUnbounded + This exception is raised if there is an infinite capacity path + from s to t in G. In this case there is no maximum flow. This + exception is also raised if the digraph G has a cycle of + negative cost and infinite capacity. Then, the cost of a flow + is unbounded below. + + See also + -------- + cost_of_flow, min_cost_flow, min_cost_flow_cost, network_simplex + + Notes + ----- + This algorithm is not guaranteed to work if edge weights or demands + are floating point numbers (overflows and roundoff errors can + cause problems). As a workaround you can use integer numbers by + multiplying the relevant edge attributes by a convenient + constant factor (eg 100). + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_edges_from( + ... [ + ... (1, 2, {"capacity": 12, "weight": 4}), + ... (1, 3, {"capacity": 20, "weight": 6}), + ... (2, 3, {"capacity": 6, "weight": -3}), + ... (2, 6, {"capacity": 14, "weight": 1}), + ... (3, 4, {"weight": 9}), + ... (3, 5, {"capacity": 10, "weight": 5}), + ... (4, 2, {"capacity": 19, "weight": 13}), + ... (4, 5, {"capacity": 4, "weight": 0}), + ... (5, 7, {"capacity": 28, "weight": 2}), + ... (6, 5, {"capacity": 11, "weight": 1}), + ... (6, 7, {"weight": 8}), + ... (7, 4, {"capacity": 6, "weight": 6}), + ... ] + ... ) + >>> mincostFlow = nx.max_flow_min_cost(G, 1, 7) + >>> mincost = nx.cost_of_flow(G, mincostFlow) + >>> mincost + 373 + >>> from networkx.algorithms.flow import maximum_flow + >>> maxFlow = maximum_flow(G, 1, 7)[1] + >>> nx.cost_of_flow(G, maxFlow) >= mincost + True + >>> mincostFlowValue = sum((mincostFlow[u][7] for u in G.predecessors(7))) - sum( + ... (mincostFlow[7][v] for v in G.successors(7)) + ... ) + >>> mincostFlowValue == nx.maximum_flow_value(G, 1, 7) + True + + """ + maxFlow = nx.maximum_flow_value(G, s, t, capacity=capacity) + H = nx.DiGraph(G) + H.add_node(s, demand=-maxFlow) + H.add_node(t, demand=maxFlow) + return min_cost_flow(H, capacity=capacity, weight=weight) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/networksimplex.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/networksimplex.py new file mode 100644 index 0000000000000000000000000000000000000000..a9822d968808eb0c7bb45794e13150ad659b311a --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/networksimplex.py @@ -0,0 +1,666 @@ +""" +Minimum cost flow algorithms on directed connected graphs. +""" + +__all__ = ["network_simplex"] + +from itertools import chain, islice, repeat +from math import ceil, sqrt + +import networkx as nx +from networkx.utils import not_implemented_for + + +class _DataEssentialsAndFunctions: + def __init__( + self, G, multigraph, demand="demand", capacity="capacity", weight="weight" + ): + # Number all nodes and edges and hereafter reference them using ONLY their numbers + self.node_list = list(G) # nodes + self.node_indices = {u: i for i, u in enumerate(self.node_list)} # node indices + self.node_demands = [ + G.nodes[u].get(demand, 0) for u in self.node_list + ] # node demands + + self.edge_sources = [] # edge sources + self.edge_targets = [] # edge targets + if multigraph: + self.edge_keys = [] # edge keys + self.edge_indices = {} # edge indices + self.edge_capacities = [] # edge capacities + self.edge_weights = [] # edge weights + + if not multigraph: + edges = G.edges(data=True) + else: + edges = G.edges(data=True, keys=True) + + inf = float("inf") + edges = (e for e in edges if e[0] != e[1] and e[-1].get(capacity, inf) != 0) + for i, e in enumerate(edges): + self.edge_sources.append(self.node_indices[e[0]]) + self.edge_targets.append(self.node_indices[e[1]]) + if multigraph: + self.edge_keys.append(e[2]) + self.edge_indices[e[:-1]] = i + self.edge_capacities.append(e[-1].get(capacity, inf)) + self.edge_weights.append(e[-1].get(weight, 0)) + + # spanning tree specific data to be initialized + + self.edge_count = None # number of edges + self.edge_flow = None # edge flows + self.node_potentials = None # node potentials + self.parent = None # parent nodes + self.parent_edge = None # edges to parents + self.subtree_size = None # subtree sizes + self.next_node_dft = None # next nodes in depth-first thread + self.prev_node_dft = None # previous nodes in depth-first thread + self.last_descendent_dft = None # last descendants in depth-first thread + self._spanning_tree_initialized = ( + False # False until initialize_spanning_tree() is called + ) + + def initialize_spanning_tree(self, n, faux_inf): + self.edge_count = len(self.edge_indices) # number of edges + self.edge_flow = list( + chain(repeat(0, self.edge_count), (abs(d) for d in self.node_demands)) + ) # edge flows + self.node_potentials = [ + faux_inf if d <= 0 else -faux_inf for d in self.node_demands + ] # node potentials + self.parent = list(chain(repeat(-1, n), [None])) # parent nodes + self.parent_edge = list( + range(self.edge_count, self.edge_count + n) + ) # edges to parents + self.subtree_size = list(chain(repeat(1, n), [n + 1])) # subtree sizes + self.next_node_dft = list( + chain(range(1, n), [-1, 0]) + ) # next nodes in depth-first thread + self.prev_node_dft = list(range(-1, n)) # previous nodes in depth-first thread + self.last_descendent_dft = list( + chain(range(n), [n - 1]) + ) # last descendants in depth-first thread + self._spanning_tree_initialized = True # True only if all the assignments pass + + def find_apex(self, p, q): + """ + Find the lowest common ancestor of nodes p and q in the spanning tree. + """ + size_p = self.subtree_size[p] + size_q = self.subtree_size[q] + while True: + while size_p < size_q: + p = self.parent[p] + size_p = self.subtree_size[p] + while size_p > size_q: + q = self.parent[q] + size_q = self.subtree_size[q] + if size_p == size_q: + if p != q: + p = self.parent[p] + size_p = self.subtree_size[p] + q = self.parent[q] + size_q = self.subtree_size[q] + else: + return p + + def trace_path(self, p, w): + """ + Returns the nodes and edges on the path from node p to its ancestor w. + """ + Wn = [p] + We = [] + while p != w: + We.append(self.parent_edge[p]) + p = self.parent[p] + Wn.append(p) + return Wn, We + + def find_cycle(self, i, p, q): + """ + Returns the nodes and edges on the cycle containing edge i == (p, q) + when the latter is added to the spanning tree. + + The cycle is oriented in the direction from p to q. + """ + w = self.find_apex(p, q) + Wn, We = self.trace_path(p, w) + Wn.reverse() + We.reverse() + if We != [i]: + We.append(i) + WnR, WeR = self.trace_path(q, w) + del WnR[-1] + Wn += WnR + We += WeR + return Wn, We + + def augment_flow(self, Wn, We, f): + """ + Augment f units of flow along a cycle represented by Wn and We. + """ + for i, p in zip(We, Wn): + if self.edge_sources[i] == p: + self.edge_flow[i] += f + else: + self.edge_flow[i] -= f + + def trace_subtree(self, p): + """ + Yield the nodes in the subtree rooted at a node p. + """ + yield p + l = self.last_descendent_dft[p] + while p != l: + p = self.next_node_dft[p] + yield p + + def remove_edge(self, s, t): + """ + Remove an edge (s, t) where parent[t] == s from the spanning tree. + """ + size_t = self.subtree_size[t] + prev_t = self.prev_node_dft[t] + last_t = self.last_descendent_dft[t] + next_last_t = self.next_node_dft[last_t] + # Remove (s, t). + self.parent[t] = None + self.parent_edge[t] = None + # Remove the subtree rooted at t from the depth-first thread. + self.next_node_dft[prev_t] = next_last_t + self.prev_node_dft[next_last_t] = prev_t + self.next_node_dft[last_t] = t + self.prev_node_dft[t] = last_t + # Update the subtree sizes and last descendants of the (old) ancestors + # of t. + while s is not None: + self.subtree_size[s] -= size_t + if self.last_descendent_dft[s] == last_t: + self.last_descendent_dft[s] = prev_t + s = self.parent[s] + + def make_root(self, q): + """ + Make a node q the root of its containing subtree. + """ + ancestors = [] + while q is not None: + ancestors.append(q) + q = self.parent[q] + ancestors.reverse() + for p, q in zip(ancestors, islice(ancestors, 1, None)): + size_p = self.subtree_size[p] + last_p = self.last_descendent_dft[p] + prev_q = self.prev_node_dft[q] + last_q = self.last_descendent_dft[q] + next_last_q = self.next_node_dft[last_q] + # Make p a child of q. + self.parent[p] = q + self.parent[q] = None + self.parent_edge[p] = self.parent_edge[q] + self.parent_edge[q] = None + self.subtree_size[p] = size_p - self.subtree_size[q] + self.subtree_size[q] = size_p + # Remove the subtree rooted at q from the depth-first thread. + self.next_node_dft[prev_q] = next_last_q + self.prev_node_dft[next_last_q] = prev_q + self.next_node_dft[last_q] = q + self.prev_node_dft[q] = last_q + if last_p == last_q: + self.last_descendent_dft[p] = prev_q + last_p = prev_q + # Add the remaining parts of the subtree rooted at p as a subtree + # of q in the depth-first thread. + self.prev_node_dft[p] = last_q + self.next_node_dft[last_q] = p + self.next_node_dft[last_p] = q + self.prev_node_dft[q] = last_p + self.last_descendent_dft[q] = last_p + + def add_edge(self, i, p, q): + """ + Add an edge (p, q) to the spanning tree where q is the root of a subtree. + """ + last_p = self.last_descendent_dft[p] + next_last_p = self.next_node_dft[last_p] + size_q = self.subtree_size[q] + last_q = self.last_descendent_dft[q] + # Make q a child of p. + self.parent[q] = p + self.parent_edge[q] = i + # Insert the subtree rooted at q into the depth-first thread. + self.next_node_dft[last_p] = q + self.prev_node_dft[q] = last_p + self.prev_node_dft[next_last_p] = last_q + self.next_node_dft[last_q] = next_last_p + # Update the subtree sizes and last descendants of the (new) ancestors + # of q. + while p is not None: + self.subtree_size[p] += size_q + if self.last_descendent_dft[p] == last_p: + self.last_descendent_dft[p] = last_q + p = self.parent[p] + + def update_potentials(self, i, p, q): + """ + Update the potentials of the nodes in the subtree rooted at a node + q connected to its parent p by an edge i. + """ + if q == self.edge_targets[i]: + d = self.node_potentials[p] - self.edge_weights[i] - self.node_potentials[q] + else: + d = self.node_potentials[p] + self.edge_weights[i] - self.node_potentials[q] + for q in self.trace_subtree(q): + self.node_potentials[q] += d + + def reduced_cost(self, i): + """Returns the reduced cost of an edge i.""" + c = ( + self.edge_weights[i] + - self.node_potentials[self.edge_sources[i]] + + self.node_potentials[self.edge_targets[i]] + ) + return c if self.edge_flow[i] == 0 else -c + + def find_entering_edges(self): + """Yield entering edges until none can be found.""" + if self.edge_count == 0: + return + + # Entering edges are found by combining Dantzig's rule and Bland's + # rule. The edges are cyclically grouped into blocks of size B. Within + # each block, Dantzig's rule is applied to find an entering edge. The + # blocks to search is determined following Bland's rule. + B = int(ceil(sqrt(self.edge_count))) # pivot block size + M = (self.edge_count + B - 1) // B # number of blocks needed to cover all edges + m = 0 # number of consecutive blocks without eligible + # entering edges + f = 0 # first edge in block + while m < M: + # Determine the next block of edges. + l = f + B + if l <= self.edge_count: + edges = range(f, l) + else: + l -= self.edge_count + edges = chain(range(f, self.edge_count), range(l)) + f = l + # Find the first edge with the lowest reduced cost. + i = min(edges, key=self.reduced_cost) + c = self.reduced_cost(i) + if c >= 0: + # No entering edge found in the current block. + m += 1 + else: + # Entering edge found. + if self.edge_flow[i] == 0: + p = self.edge_sources[i] + q = self.edge_targets[i] + else: + p = self.edge_targets[i] + q = self.edge_sources[i] + yield i, p, q + m = 0 + # All edges have nonnegative reduced costs. The current flow is + # optimal. + + def residual_capacity(self, i, p): + """Returns the residual capacity of an edge i in the direction away + from its endpoint p. + """ + return ( + self.edge_capacities[i] - self.edge_flow[i] + if self.edge_sources[i] == p + else self.edge_flow[i] + ) + + def find_leaving_edge(self, Wn, We): + """Returns the leaving edge in a cycle represented by Wn and We.""" + j, s = min( + zip(reversed(We), reversed(Wn)), + key=lambda i_p: self.residual_capacity(*i_p), + ) + t = self.edge_targets[j] if self.edge_sources[j] == s else self.edge_sources[j] + return j, s, t + + +@not_implemented_for("undirected") +@nx._dispatchable( + node_attrs="demand", edge_attrs={"capacity": float("inf"), "weight": 0} +) +def network_simplex(G, demand="demand", capacity="capacity", weight="weight"): + r"""Find a minimum cost flow satisfying all demands in digraph G. + + This is a primal network simplex algorithm that uses the leaving + arc rule to prevent cycling. + + G is a digraph with edge costs and capacities and in which nodes + have demand, i.e., they want to send or receive some amount of + flow. A negative demand means that the node wants to send flow, a + positive demand means that the node want to receive flow. A flow on + the digraph G satisfies all demand if the net flow into each node + is equal to the demand of that node. + + Parameters + ---------- + G : NetworkX graph + DiGraph on which a minimum cost flow satisfying all demands is + to be found. + + demand : string + Nodes of the graph G are expected to have an attribute demand + that indicates how much flow a node wants to send (negative + demand) or receive (positive demand). Note that the sum of the + demands should be 0 otherwise the problem in not feasible. If + this attribute is not present, a node is considered to have 0 + demand. Default value: 'demand'. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + weight : string + Edges of the graph G are expected to have an attribute weight + that indicates the cost incurred by sending one unit of flow on + that edge. If not present, the weight is considered to be 0. + Default value: 'weight'. + + Returns + ------- + flowCost : integer, float + Cost of a minimum cost flow satisfying all demands. + + flowDict : dictionary + Dictionary of dictionaries keyed by nodes such that + flowDict[u][v] is the flow edge (u, v). + + Raises + ------ + NetworkXError + This exception is raised if the input graph is not directed or + not connected. + + NetworkXUnfeasible + This exception is raised in the following situations: + + * The sum of the demands is not zero. Then, there is no + flow satisfying all demands. + * There is no flow satisfying all demand. + + NetworkXUnbounded + This exception is raised if the digraph G has a cycle of + negative cost and infinite capacity. Then, the cost of a flow + satisfying all demands is unbounded below. + + Notes + ----- + This algorithm is not guaranteed to work if edge weights or demands + are floating point numbers (overflows and roundoff errors can + cause problems). As a workaround you can use integer numbers by + multiplying the relevant edge attributes by a convenient + constant factor (eg 100). + + See also + -------- + cost_of_flow, max_flow_min_cost, min_cost_flow, min_cost_flow_cost + + Examples + -------- + A simple example of a min cost flow problem. + + >>> G = nx.DiGraph() + >>> G.add_node("a", demand=-5) + >>> G.add_node("d", demand=5) + >>> G.add_edge("a", "b", weight=3, capacity=4) + >>> G.add_edge("a", "c", weight=6, capacity=10) + >>> G.add_edge("b", "d", weight=1, capacity=9) + >>> G.add_edge("c", "d", weight=2, capacity=5) + >>> flowCost, flowDict = nx.network_simplex(G) + >>> flowCost + 24 + >>> flowDict + {'a': {'b': 4, 'c': 1}, 'd': {}, 'b': {'d': 4}, 'c': {'d': 1}} + + The mincost flow algorithm can also be used to solve shortest path + problems. To find the shortest path between two nodes u and v, + give all edges an infinite capacity, give node u a demand of -1 and + node v a demand a 1. Then run the network simplex. The value of a + min cost flow will be the distance between u and v and edges + carrying positive flow will indicate the path. + + >>> G = nx.DiGraph() + >>> G.add_weighted_edges_from( + ... [ + ... ("s", "u", 10), + ... ("s", "x", 5), + ... ("u", "v", 1), + ... ("u", "x", 2), + ... ("v", "y", 1), + ... ("x", "u", 3), + ... ("x", "v", 5), + ... ("x", "y", 2), + ... ("y", "s", 7), + ... ("y", "v", 6), + ... ] + ... ) + >>> G.add_node("s", demand=-1) + >>> G.add_node("v", demand=1) + >>> flowCost, flowDict = nx.network_simplex(G) + >>> flowCost == nx.shortest_path_length(G, "s", "v", weight="weight") + True + >>> sorted([(u, v) for u in flowDict for v in flowDict[u] if flowDict[u][v] > 0]) + [('s', 'x'), ('u', 'v'), ('x', 'u')] + >>> nx.shortest_path(G, "s", "v", weight="weight") + ['s', 'x', 'u', 'v'] + + It is possible to change the name of the attributes used for the + algorithm. + + >>> G = nx.DiGraph() + >>> G.add_node("p", spam=-4) + >>> G.add_node("q", spam=2) + >>> G.add_node("a", spam=-2) + >>> G.add_node("d", spam=-1) + >>> G.add_node("t", spam=2) + >>> G.add_node("w", spam=3) + >>> G.add_edge("p", "q", cost=7, vacancies=5) + >>> G.add_edge("p", "a", cost=1, vacancies=4) + >>> G.add_edge("q", "d", cost=2, vacancies=3) + >>> G.add_edge("t", "q", cost=1, vacancies=2) + >>> G.add_edge("a", "t", cost=2, vacancies=4) + >>> G.add_edge("d", "w", cost=3, vacancies=4) + >>> G.add_edge("t", "w", cost=4, vacancies=1) + >>> flowCost, flowDict = nx.network_simplex( + ... G, demand="spam", capacity="vacancies", weight="cost" + ... ) + >>> flowCost + 37 + >>> flowDict + {'p': {'q': 2, 'a': 2}, 'q': {'d': 1}, 'a': {'t': 4}, 'd': {'w': 2}, 't': {'q': 1, 'w': 1}, 'w': {}} + + References + ---------- + .. [1] Z. Kiraly, P. Kovacs. + Efficient implementation of minimum-cost flow algorithms. + Acta Universitatis Sapientiae, Informatica 4(1):67--118. 2012. + .. [2] R. Barr, F. Glover, D. Klingman. + Enhancement of spanning tree labeling procedures for network + optimization. + INFOR 17(1):16--34. 1979. + """ + ########################################################################### + # Problem essentials extraction and sanity check + ########################################################################### + + if len(G) == 0: + raise nx.NetworkXError("graph has no nodes") + + multigraph = G.is_multigraph() + + # extracting data essential to problem + DEAF = _DataEssentialsAndFunctions( + G, multigraph, demand=demand, capacity=capacity, weight=weight + ) + + ########################################################################### + # Quick Error Detection + ########################################################################### + + inf = float("inf") + for u, d in zip(DEAF.node_list, DEAF.node_demands): + if abs(d) == inf: + raise nx.NetworkXError(f"node {u!r} has infinite demand") + for e, w in zip(DEAF.edge_indices, DEAF.edge_weights): + if abs(w) == inf: + raise nx.NetworkXError(f"edge {e!r} has infinite weight") + if not multigraph: + edges = nx.selfloop_edges(G, data=True) + else: + edges = nx.selfloop_edges(G, data=True, keys=True) + for e in edges: + if abs(e[-1].get(weight, 0)) == inf: + raise nx.NetworkXError(f"edge {e[:-1]!r} has infinite weight") + + ########################################################################### + # Quick Infeasibility Detection + ########################################################################### + + if sum(DEAF.node_demands) != 0: + raise nx.NetworkXUnfeasible("total node demand is not zero") + for e, c in zip(DEAF.edge_indices, DEAF.edge_capacities): + if c < 0: + raise nx.NetworkXUnfeasible(f"edge {e!r} has negative capacity") + if not multigraph: + edges = nx.selfloop_edges(G, data=True) + else: + edges = nx.selfloop_edges(G, data=True, keys=True) + for e in edges: + if e[-1].get(capacity, inf) < 0: + raise nx.NetworkXUnfeasible(f"edge {e[:-1]!r} has negative capacity") + + ########################################################################### + # Initialization + ########################################################################### + + # Add a dummy node -1 and connect all existing nodes to it with infinite- + # capacity dummy edges. Node -1 will serve as the root of the + # spanning tree of the network simplex method. The new edges will used to + # trivially satisfy the node demands and create an initial strongly + # feasible spanning tree. + for i, d in enumerate(DEAF.node_demands): + # Must be greater-than here. Zero-demand nodes must have + # edges pointing towards the root to ensure strong feasibility. + if d > 0: + DEAF.edge_sources.append(-1) + DEAF.edge_targets.append(i) + else: + DEAF.edge_sources.append(i) + DEAF.edge_targets.append(-1) + faux_inf = ( + 3 + * max( + chain( + [ + sum(c for c in DEAF.edge_capacities if c < inf), + sum(abs(w) for w in DEAF.edge_weights), + ], + (abs(d) for d in DEAF.node_demands), + ) + ) + or 1 + ) + + n = len(DEAF.node_list) # number of nodes + DEAF.edge_weights.extend(repeat(faux_inf, n)) + DEAF.edge_capacities.extend(repeat(faux_inf, n)) + + # Construct the initial spanning tree. + DEAF.initialize_spanning_tree(n, faux_inf) + + ########################################################################### + # Pivot loop + ########################################################################### + + for i, p, q in DEAF.find_entering_edges(): + Wn, We = DEAF.find_cycle(i, p, q) + j, s, t = DEAF.find_leaving_edge(Wn, We) + DEAF.augment_flow(Wn, We, DEAF.residual_capacity(j, s)) + # Do nothing more if the entering edge is the same as the leaving edge. + if i != j: + if DEAF.parent[t] != s: + # Ensure that s is the parent of t. + s, t = t, s + if We.index(i) > We.index(j): + # Ensure that q is in the subtree rooted at t. + p, q = q, p + DEAF.remove_edge(s, t) + DEAF.make_root(q) + DEAF.add_edge(i, p, q) + DEAF.update_potentials(i, p, q) + + ########################################################################### + # Infeasibility and unboundedness detection + ########################################################################### + + if any(DEAF.edge_flow[i] != 0 for i in range(-n, 0)): + raise nx.NetworkXUnfeasible("no flow satisfies all node demands") + + if any(DEAF.edge_flow[i] * 2 >= faux_inf for i in range(DEAF.edge_count)) or any( + e[-1].get(capacity, inf) == inf and e[-1].get(weight, 0) < 0 + for e in nx.selfloop_edges(G, data=True) + ): + raise nx.NetworkXUnbounded("negative cycle with infinite capacity found") + + ########################################################################### + # Flow cost calculation and flow dict construction + ########################################################################### + + del DEAF.edge_flow[DEAF.edge_count :] + flow_cost = sum(w * x for w, x in zip(DEAF.edge_weights, DEAF.edge_flow)) + flow_dict = {n: {} for n in DEAF.node_list} + + def add_entry(e): + """Add a flow dict entry.""" + d = flow_dict[e[0]] + for k in e[1:-2]: + try: + d = d[k] + except KeyError: + t = {} + d[k] = t + d = t + d[e[-2]] = e[-1] + + DEAF.edge_sources = ( + DEAF.node_list[s] for s in DEAF.edge_sources + ) # Use original nodes. + DEAF.edge_targets = ( + DEAF.node_list[t] for t in DEAF.edge_targets + ) # Use original nodes. + if not multigraph: + for e in zip(DEAF.edge_sources, DEAF.edge_targets, DEAF.edge_flow): + add_entry(e) + edges = G.edges(data=True) + else: + for e in zip( + DEAF.edge_sources, DEAF.edge_targets, DEAF.edge_keys, DEAF.edge_flow + ): + add_entry(e) + edges = G.edges(data=True, keys=True) + for e in edges: + if e[0] != e[1]: + if e[-1].get(capacity, inf) == 0: + add_entry(e[:-1] + (0,)) + else: + w = e[-1].get(weight, 0) + if w >= 0: + add_entry(e[:-1] + (0,)) + else: + c = e[-1][capacity] + flow_cost += w * c + add_entry(e[:-1] + (c,)) + + return flow_cost, flow_dict diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/preflowpush.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/preflowpush.py new file mode 100644 index 0000000000000000000000000000000000000000..42cadc2e2db6ecfb5a347499c89d5ae77f6af3d8 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/preflowpush.py @@ -0,0 +1,425 @@ +""" +Highest-label preflow-push algorithm for maximum flow problems. +""" + +from collections import deque +from itertools import islice + +import networkx as nx + +from ...utils import arbitrary_element +from .utils import ( + CurrentEdge, + GlobalRelabelThreshold, + Level, + build_residual_network, + detect_unboundedness, +) + +__all__ = ["preflow_push"] + + +def preflow_push_impl(G, s, t, capacity, residual, global_relabel_freq, value_only): + """Implementation of the highest-label preflow-push algorithm.""" + if s not in G: + raise nx.NetworkXError(f"node {str(s)} not in graph") + if t not in G: + raise nx.NetworkXError(f"node {str(t)} not in graph") + if s == t: + raise nx.NetworkXError("source and sink are the same node") + + if global_relabel_freq is None: + global_relabel_freq = 0 + if global_relabel_freq < 0: + raise nx.NetworkXError("global_relabel_freq must be nonnegative.") + + if residual is None: + R = build_residual_network(G, capacity) + else: + R = residual + + detect_unboundedness(R, s, t) + + R_nodes = R.nodes + R_pred = R.pred + R_succ = R.succ + + # Initialize/reset the residual network. + for u in R: + R_nodes[u]["excess"] = 0 + for e in R_succ[u].values(): + e["flow"] = 0 + + def reverse_bfs(src): + """Perform a reverse breadth-first search from src in the residual + network. + """ + heights = {src: 0} + q = deque([(src, 0)]) + while q: + u, height = q.popleft() + height += 1 + for v, attr in R_pred[u].items(): + if v not in heights and attr["flow"] < attr["capacity"]: + heights[v] = height + q.append((v, height)) + return heights + + # Initialize heights of the nodes. + heights = reverse_bfs(t) + + if s not in heights: + # t is not reachable from s in the residual network. The maximum flow + # must be zero. + R.graph["flow_value"] = 0 + return R + + n = len(R) + # max_height represents the height of the highest level below level n with + # at least one active node. + max_height = max(heights[u] for u in heights if u != s) + heights[s] = n + + grt = GlobalRelabelThreshold(n, R.size(), global_relabel_freq) + + # Initialize heights and 'current edge' data structures of the nodes. + for u in R: + R_nodes[u]["height"] = heights[u] if u in heights else n + 1 + R_nodes[u]["curr_edge"] = CurrentEdge(R_succ[u]) + + def push(u, v, flow): + """Push flow units of flow from u to v.""" + R_succ[u][v]["flow"] += flow + R_succ[v][u]["flow"] -= flow + R_nodes[u]["excess"] -= flow + R_nodes[v]["excess"] += flow + + # The maximum flow must be nonzero now. Initialize the preflow by + # saturating all edges emanating from s. + for u, attr in R_succ[s].items(): + flow = attr["capacity"] + if flow > 0: + push(s, u, flow) + + # Partition nodes into levels. + levels = [Level() for i in range(2 * n)] + for u in R: + if u != s and u != t: + level = levels[R_nodes[u]["height"]] + if R_nodes[u]["excess"] > 0: + level.active.add(u) + else: + level.inactive.add(u) + + def activate(v): + """Move a node from the inactive set to the active set of its level.""" + if v != s and v != t: + level = levels[R_nodes[v]["height"]] + if v in level.inactive: + level.inactive.remove(v) + level.active.add(v) + + def relabel(u): + """Relabel a node to create an admissible edge.""" + grt.add_work(len(R_succ[u])) + return ( + min( + R_nodes[v]["height"] + for v, attr in R_succ[u].items() + if attr["flow"] < attr["capacity"] + ) + + 1 + ) + + def discharge(u, is_phase1): + """Discharge a node until it becomes inactive or, during phase 1 (see + below), its height reaches at least n. The node is known to have the + largest height among active nodes. + """ + height = R_nodes[u]["height"] + curr_edge = R_nodes[u]["curr_edge"] + # next_height represents the next height to examine after discharging + # the current node. During phase 1, it is capped to below n. + next_height = height + levels[height].active.remove(u) + while True: + v, attr = curr_edge.get() + if height == R_nodes[v]["height"] + 1 and attr["flow"] < attr["capacity"]: + flow = min(R_nodes[u]["excess"], attr["capacity"] - attr["flow"]) + push(u, v, flow) + activate(v) + if R_nodes[u]["excess"] == 0: + # The node has become inactive. + levels[height].inactive.add(u) + break + try: + curr_edge.move_to_next() + except StopIteration: + # We have run off the end of the adjacency list, and there can + # be no more admissible edges. Relabel the node to create one. + height = relabel(u) + if is_phase1 and height >= n - 1: + # Although the node is still active, with a height at least + # n - 1, it is now known to be on the s side of the minimum + # s-t cut. Stop processing it until phase 2. + levels[height].active.add(u) + break + # The first relabel operation after global relabeling may not + # increase the height of the node since the 'current edge' data + # structure is not rewound. Use height instead of (height - 1) + # in case other active nodes at the same level are missed. + next_height = height + R_nodes[u]["height"] = height + return next_height + + def gap_heuristic(height): + """Apply the gap heuristic.""" + # Move all nodes at levels (height + 1) to max_height to level n + 1. + for level in islice(levels, height + 1, max_height + 1): + for u in level.active: + R_nodes[u]["height"] = n + 1 + for u in level.inactive: + R_nodes[u]["height"] = n + 1 + levels[n + 1].active.update(level.active) + level.active.clear() + levels[n + 1].inactive.update(level.inactive) + level.inactive.clear() + + def global_relabel(from_sink): + """Apply the global relabeling heuristic.""" + src = t if from_sink else s + heights = reverse_bfs(src) + if not from_sink: + # s must be reachable from t. Remove t explicitly. + del heights[t] + max_height = max(heights.values()) + if from_sink: + # Also mark nodes from which t is unreachable for relabeling. This + # serves the same purpose as the gap heuristic. + for u in R: + if u not in heights and R_nodes[u]["height"] < n: + heights[u] = n + 1 + else: + # Shift the computed heights because the height of s is n. + for u in heights: + heights[u] += n + max_height += n + del heights[src] + for u, new_height in heights.items(): + old_height = R_nodes[u]["height"] + if new_height != old_height: + if u in levels[old_height].active: + levels[old_height].active.remove(u) + levels[new_height].active.add(u) + else: + levels[old_height].inactive.remove(u) + levels[new_height].inactive.add(u) + R_nodes[u]["height"] = new_height + return max_height + + # Phase 1: Find the maximum preflow by pushing as much flow as possible to + # t. + + height = max_height + while height > 0: + # Discharge active nodes in the current level. + while True: + level = levels[height] + if not level.active: + # All active nodes in the current level have been discharged. + # Move to the next lower level. + height -= 1 + break + # Record the old height and level for the gap heuristic. + old_height = height + old_level = level + u = arbitrary_element(level.active) + height = discharge(u, True) + if grt.is_reached(): + # Global relabeling heuristic: Recompute the exact heights of + # all nodes. + height = global_relabel(True) + max_height = height + grt.clear_work() + elif not old_level.active and not old_level.inactive: + # Gap heuristic: If the level at old_height is empty (a 'gap'), + # a minimum cut has been identified. All nodes with heights + # above old_height can have their heights set to n + 1 and not + # be further processed before a maximum preflow is found. + gap_heuristic(old_height) + height = old_height - 1 + max_height = height + else: + # Update the height of the highest level with at least one + # active node. + max_height = max(max_height, height) + + # A maximum preflow has been found. The excess at t is the maximum flow + # value. + if value_only: + R.graph["flow_value"] = R_nodes[t]["excess"] + return R + + # Phase 2: Convert the maximum preflow into a maximum flow by returning the + # excess to s. + + # Relabel all nodes so that they have accurate heights. + height = global_relabel(False) + grt.clear_work() + + # Continue to discharge the active nodes. + while height > n: + # Discharge active nodes in the current level. + while True: + level = levels[height] + if not level.active: + # All active nodes in the current level have been discharged. + # Move to the next lower level. + height -= 1 + break + u = arbitrary_element(level.active) + height = discharge(u, False) + if grt.is_reached(): + # Global relabeling heuristic. + height = global_relabel(False) + grt.clear_work() + + R.graph["flow_value"] = R_nodes[t]["excess"] + return R + + +@nx._dispatchable(edge_attrs={"capacity": float("inf")}, returns_graph=True) +def preflow_push( + G, s, t, capacity="capacity", residual=None, global_relabel_freq=1, value_only=False +): + r"""Find a maximum single-commodity flow using the highest-label + preflow-push algorithm. + + This function returns the residual network resulting after computing + the maximum flow. See below for details about the conventions + NetworkX uses for defining residual networks. + + This algorithm has a running time of $O(n^2 \sqrt{m})$ for $n$ nodes and + $m$ edges. + + + Parameters + ---------- + G : NetworkX graph + Edges of the graph are expected to have an attribute called + 'capacity'. If this attribute is not present, the edge is + considered to have infinite capacity. + + s : node + Source node for the flow. + + t : node + Sink node for the flow. + + capacity : string + Edges of the graph G are expected to have an attribute capacity + that indicates how much flow the edge can support. If this + attribute is not present, the edge is considered to have + infinite capacity. Default value: 'capacity'. + + residual : NetworkX graph + Residual network on which the algorithm is to be executed. If None, a + new residual network is created. Default value: None. + + global_relabel_freq : integer, float + Relative frequency of applying the global relabeling heuristic to speed + up the algorithm. If it is None, the heuristic is disabled. Default + value: 1. + + value_only : bool + If False, compute a maximum flow; otherwise, compute a maximum preflow + which is enough for computing the maximum flow value. Default value: + False. + + Returns + ------- + R : NetworkX DiGraph + Residual network after computing the maximum flow. + + Raises + ------ + NetworkXError + The algorithm does not support MultiGraph and MultiDiGraph. If + the input graph is an instance of one of these two classes, a + NetworkXError is raised. + + NetworkXUnbounded + If the graph has a path of infinite capacity, the value of a + feasible flow on the graph is unbounded above and the function + raises a NetworkXUnbounded. + + See also + -------- + :meth:`maximum_flow` + :meth:`minimum_cut` + :meth:`edmonds_karp` + :meth:`shortest_augmenting_path` + + Notes + ----- + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. For each node :samp:`u` in :samp:`R`, + :samp:`R.nodes[u]['excess']` represents the difference between flow into + :samp:`u` and flow out of :samp:`u`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. Reachability to :samp:`t` using + only edges :samp:`(u, v)` such that + :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + Examples + -------- + >>> from networkx.algorithms.flow import preflow_push + + The functions that implement flow algorithms and output a residual + network, such as this one, are not imported to the base NetworkX + namespace, so you have to explicitly import them from the flow package. + + >>> G = nx.DiGraph() + >>> G.add_edge("x", "a", capacity=3.0) + >>> G.add_edge("x", "b", capacity=1.0) + >>> G.add_edge("a", "c", capacity=3.0) + >>> G.add_edge("b", "c", capacity=5.0) + >>> G.add_edge("b", "d", capacity=4.0) + >>> G.add_edge("d", "e", capacity=2.0) + >>> G.add_edge("c", "y", capacity=2.0) + >>> G.add_edge("e", "y", capacity=3.0) + >>> R = preflow_push(G, "x", "y") + >>> flow_value = nx.maximum_flow_value(G, "x", "y") + >>> flow_value == R.graph["flow_value"] + True + >>> # preflow_push also stores the maximum flow value + >>> # in the excess attribute of the sink node t + >>> flow_value == R.nodes["y"]["excess"] + True + >>> # For some problems, you might only want to compute a + >>> # maximum preflow. + >>> R = preflow_push(G, "x", "y", value_only=True) + >>> flow_value == R.graph["flow_value"] + True + >>> flow_value == R.nodes["y"]["excess"] + True + + """ + R = preflow_push_impl(G, s, t, capacity, residual, global_relabel_freq, value_only) + R.graph["algorithm"] = "preflow_push" + nx._clear_cache(R) + return R diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/__init__.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/__init__.py new file mode 100644 index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/__pycache__/__init__.cpython-310.pyc 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b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_gomory_hu.py new file mode 100644 index 0000000000000000000000000000000000000000..1649ec82c719226e9caa68268d8953f7cae6ef74 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_gomory_hu.py @@ -0,0 +1,128 @@ +from itertools import combinations + +import pytest + +import networkx as nx +from networkx.algorithms.flow import ( + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +) + +flow_funcs = [ + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +] + + +class TestGomoryHuTree: + def minimum_edge_weight(self, T, u, v): + path = nx.shortest_path(T, u, v, weight="weight") + return min((T[u][v]["weight"], (u, v)) for (u, v) in zip(path, path[1:])) + + def compute_cutset(self, G, T_orig, edge): + T = T_orig.copy() + T.remove_edge(*edge) + U, V = list(nx.connected_components(T)) + cutset = set() + for x, nbrs in ((n, G[n]) for n in U): + cutset.update((x, y) for y in nbrs if y in V) + return cutset + + def test_default_flow_function_karate_club_graph(self): + G = nx.karate_club_graph() + nx.set_edge_attributes(G, 1, "capacity") + T = nx.gomory_hu_tree(G) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_karate_club_graph(self): + G = nx.karate_club_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_davis_southern_women_graph(self): + G = nx.davis_southern_women_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_florentine_families_graph(self): + G = nx.florentine_families_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + @pytest.mark.slow + def test_les_miserables_graph_cutset(self): + G = nx.les_miserables_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_karate_club_graph_cutset(self): + G = nx.karate_club_graph() + nx.set_edge_attributes(G, 1, "capacity") + T = nx.gomory_hu_tree(G) + assert nx.is_tree(T) + u, v = 0, 33 + cut_value, edge = self.minimum_edge_weight(T, u, v) + cutset = self.compute_cutset(G, T, edge) + assert cut_value == len(cutset) + + def test_wikipedia_example(self): + # Example from https://en.wikipedia.org/wiki/Gomory%E2%80%93Hu_tree + G = nx.Graph() + G.add_weighted_edges_from( + ( + (0, 1, 1), + (0, 2, 7), + (1, 2, 1), + (1, 3, 3), + (1, 4, 2), + (2, 4, 4), + (3, 4, 1), + (3, 5, 6), + (4, 5, 2), + ) + ) + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, capacity="weight", flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v, capacity="weight") == cut_value + + def test_directed_raises(self): + with pytest.raises(nx.NetworkXNotImplemented): + G = nx.DiGraph() + T = nx.gomory_hu_tree(G) + + def test_empty_raises(self): + with pytest.raises(nx.NetworkXError): + G = nx.empty_graph() + T = nx.gomory_hu_tree(G) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_maxflow.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_maxflow.py new file mode 100644 index 0000000000000000000000000000000000000000..d7305a7b6320ef1b55c682386cd7320f33a78994 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_maxflow.py @@ -0,0 +1,573 @@ +"""Maximum flow algorithms test suite.""" + +import pytest + +import networkx as nx +from networkx.algorithms.flow import ( + boykov_kolmogorov, + build_flow_dict, + build_residual_network, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +) + +flow_funcs = { + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +} + +max_min_funcs = {nx.maximum_flow, nx.minimum_cut} +flow_value_funcs = {nx.maximum_flow_value, nx.minimum_cut_value} +interface_funcs = max_min_funcs | flow_value_funcs +all_funcs = flow_funcs | interface_funcs + + +def compute_cutset(G, partition): + reachable, non_reachable = partition + cutset = set() + for u, nbrs in ((n, G[n]) for n in reachable): + cutset.update((u, v) for v in nbrs if v in non_reachable) + return cutset + + +def validate_flows(G, s, t, flowDict, solnValue, capacity, flow_func): + errmsg = f"Assertion failed in function: {flow_func.__name__}" + assert set(G) == set(flowDict), errmsg + for u in G: + assert set(G[u]) == set(flowDict[u]), errmsg + excess = {u: 0 for u in flowDict} + for u in flowDict: + for v, flow in flowDict[u].items(): + if capacity in G[u][v]: + assert flow <= G[u][v][capacity] + assert flow >= 0, errmsg + excess[u] -= flow + excess[v] += flow + for u, exc in excess.items(): + if u == s: + assert exc == -solnValue, errmsg + elif u == t: + assert exc == solnValue, errmsg + else: + assert exc == 0, errmsg + + +def validate_cuts(G, s, t, solnValue, partition, capacity, flow_func): + errmsg = f"Assertion failed in function: {flow_func.__name__}" + assert all(n in G for n in partition[0]), errmsg + assert all(n in G for n in partition[1]), errmsg + cutset = compute_cutset(G, partition) + assert all(G.has_edge(u, v) for (u, v) in cutset), errmsg + assert solnValue == sum(G[u][v][capacity] for (u, v) in cutset), errmsg + H = G.copy() + H.remove_edges_from(cutset) + if not G.is_directed(): + assert not nx.is_connected(H), errmsg + else: + assert not nx.is_strongly_connected(H), errmsg + + +def compare_flows_and_cuts(G, s, t, solnValue, capacity="capacity"): + for flow_func in flow_funcs: + errmsg = f"Assertion failed in function: {flow_func.__name__}" + R = flow_func(G, s, t, capacity) + # Test both legacy and new implementations. + flow_value = R.graph["flow_value"] + flow_dict = build_flow_dict(G, R) + assert flow_value == solnValue, errmsg + validate_flows(G, s, t, flow_dict, solnValue, capacity, flow_func) + # Minimum cut + cut_value, partition = nx.minimum_cut( + G, s, t, capacity=capacity, flow_func=flow_func + ) + validate_cuts(G, s, t, solnValue, partition, capacity, flow_func) + + +class TestMaxflowMinCutCommon: + def test_graph1(self): + # Trivial undirected graph + G = nx.Graph() + G.add_edge(1, 2, capacity=1.0) + + # solution flows + # {1: {2: 1.0}, 2: {1: 1.0}} + + compare_flows_and_cuts(G, 1, 2, 1.0) + + def test_graph2(self): + # A more complex undirected graph + # adapted from https://web.archive.org/web/20220815055650/https://www.topcoder.com/thrive/articles/Maximum%20Flow:%20Part%20One + G = nx.Graph() + G.add_edge("x", "a", capacity=3.0) + G.add_edge("x", "b", capacity=1.0) + G.add_edge("a", "c", capacity=3.0) + G.add_edge("b", "c", capacity=5.0) + G.add_edge("b", "d", capacity=4.0) + G.add_edge("d", "e", capacity=2.0) + G.add_edge("c", "y", capacity=2.0) + G.add_edge("e", "y", capacity=3.0) + + # H + # { + # "x": {"a": 3, "b": 1}, + # "a": {"c": 3, "x": 3}, + # "b": {"c": 1, "d": 2, "x": 1}, + # "c": {"a": 3, "b": 1, "y": 2}, + # "d": {"b": 2, "e": 2}, + # "e": {"d": 2, "y": 2}, + # "y": {"c": 2, "e": 2}, + # } + + compare_flows_and_cuts(G, "x", "y", 4.0) + + def test_digraph1(self): + # The classic directed graph example + G = nx.DiGraph() + G.add_edge("a", "b", capacity=1000.0) + G.add_edge("a", "c", capacity=1000.0) + G.add_edge("b", "c", capacity=1.0) + G.add_edge("b", "d", capacity=1000.0) + G.add_edge("c", "d", capacity=1000.0) + + # H + # { + # "a": {"b": 1000.0, "c": 1000.0}, + # "b": {"c": 0, "d": 1000.0}, + # "c": {"d": 1000.0}, + # "d": {}, + # } + + compare_flows_and_cuts(G, "a", "d", 2000.0) + + def test_digraph2(self): + # An example in which some edges end up with zero flow. + G = nx.DiGraph() + G.add_edge("s", "b", capacity=2) + G.add_edge("s", "c", capacity=1) + G.add_edge("c", "d", capacity=1) + G.add_edge("d", "a", capacity=1) + G.add_edge("b", "a", capacity=2) + G.add_edge("a", "t", capacity=2) + + # H + # { + # "s": {"b": 2, "c": 0}, + # "c": {"d": 0}, + # "d": {"a": 0}, + # "b": {"a": 2}, + # "a": {"t": 2}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 2) + + def test_digraph3(self): + # A directed graph example from Cormen et al. + G = nx.DiGraph() + G.add_edge("s", "v1", capacity=16.0) + G.add_edge("s", "v2", capacity=13.0) + G.add_edge("v1", "v2", capacity=10.0) + G.add_edge("v2", "v1", capacity=4.0) + G.add_edge("v1", "v3", capacity=12.0) + G.add_edge("v3", "v2", capacity=9.0) + G.add_edge("v2", "v4", capacity=14.0) + G.add_edge("v4", "v3", capacity=7.0) + G.add_edge("v3", "t", capacity=20.0) + G.add_edge("v4", "t", capacity=4.0) + + # H + # { + # "s": {"v1": 12.0, "v2": 11.0}, + # "v2": {"v1": 0, "v4": 11.0}, + # "v1": {"v2": 0, "v3": 12.0}, + # "v3": {"v2": 0, "t": 19.0}, + # "v4": {"v3": 7.0, "t": 4.0}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 23.0) + + def test_digraph4(self): + # A more complex directed graph + # from https://web.archive.org/web/20220815055650/https://www.topcoder.com/thrive/articles/Maximum%20Flow:%20Part%20One + G = nx.DiGraph() + G.add_edge("x", "a", capacity=3.0) + G.add_edge("x", "b", capacity=1.0) + G.add_edge("a", "c", capacity=3.0) + G.add_edge("b", "c", capacity=5.0) + G.add_edge("b", "d", capacity=4.0) + G.add_edge("d", "e", capacity=2.0) + G.add_edge("c", "y", capacity=2.0) + G.add_edge("e", "y", capacity=3.0) + + # H + # { + # "x": {"a": 2.0, "b": 1.0}, + # "a": {"c": 2.0}, + # "b": {"c": 0, "d": 1.0}, + # "c": {"y": 2.0}, + # "d": {"e": 1.0}, + # "e": {"y": 1.0}, + # "y": {}, + # } + + compare_flows_and_cuts(G, "x", "y", 3.0) + + def test_wikipedia_dinitz_example(self): + # Nice example from https://en.wikipedia.org/wiki/Dinic's_algorithm + G = nx.DiGraph() + G.add_edge("s", 1, capacity=10) + G.add_edge("s", 2, capacity=10) + G.add_edge(1, 3, capacity=4) + G.add_edge(1, 4, capacity=8) + G.add_edge(1, 2, capacity=2) + G.add_edge(2, 4, capacity=9) + G.add_edge(3, "t", capacity=10) + G.add_edge(4, 3, capacity=6) + G.add_edge(4, "t", capacity=10) + + # solution flows + # { + # 1: {2: 0, 3: 4, 4: 6}, + # 2: {4: 9}, + # 3: {"t": 9}, + # 4: {3: 5, "t": 10}, + # "s": {1: 10, 2: 9}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 19) + + def test_optional_capacity(self): + # Test optional capacity parameter. + G = nx.DiGraph() + G.add_edge("x", "a", spam=3.0) + G.add_edge("x", "b", spam=1.0) + G.add_edge("a", "c", spam=3.0) + G.add_edge("b", "c", spam=5.0) + G.add_edge("b", "d", spam=4.0) + G.add_edge("d", "e", spam=2.0) + G.add_edge("c", "y", spam=2.0) + G.add_edge("e", "y", spam=3.0) + + # solution flows + # { + # "x": {"a": 2.0, "b": 1.0}, + # "a": {"c": 2.0}, + # "b": {"c": 0, "d": 1.0}, + # "c": {"y": 2.0}, + # "d": {"e": 1.0}, + # "e": {"y": 1.0}, + # "y": {}, + # } + solnValue = 3.0 + s = "x" + t = "y" + + compare_flows_and_cuts(G, s, t, solnValue, capacity="spam") + + def test_digraph_infcap_edges(self): + # DiGraph with infinite capacity edges + G = nx.DiGraph() + G.add_edge("s", "a") + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c", capacity=25) + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t") + + # H + # { + # "s": {"a": 85, "b": 12}, + # "a": {"c": 25, "t": 60}, + # "b": {"c": 12}, + # "c": {"t": 37}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 97) + + # DiGraph with infinite capacity digon + G = nx.DiGraph() + G.add_edge("s", "a", capacity=85) + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c") + G.add_edge("c", "a") + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t", capacity=37) + + # H + # { + # "s": {"a": 85, "b": 12}, + # "a": {"c": 25, "t": 60}, + # "c": {"a": 0, "t": 37}, + # "b": {"c": 12}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 97) + + def test_digraph_infcap_path(self): + # Graph with infinite capacity (s, t)-path + G = nx.DiGraph() + G.add_edge("s", "a") + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c") + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t") + + for flow_func in all_funcs: + pytest.raises(nx.NetworkXUnbounded, flow_func, G, "s", "t") + + def test_graph_infcap_edges(self): + # Undirected graph with infinite capacity edges + G = nx.Graph() + G.add_edge("s", "a") + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c", capacity=25) + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t") + + # H + # { + # "s": {"a": 85, "b": 12}, + # "a": {"c": 25, "s": 85, "t": 60}, + # "b": {"c": 12, "s": 12}, + # "c": {"a": 25, "b": 12, "t": 37}, + # "t": {"a": 60, "c": 37}, + # } + + compare_flows_and_cuts(G, "s", "t", 97) + + def test_digraph5(self): + # From ticket #429 by mfrasca. + G = nx.DiGraph() + G.add_edge("s", "a", capacity=2) + G.add_edge("s", "b", capacity=2) + G.add_edge("a", "b", capacity=5) + G.add_edge("a", "t", capacity=1) + G.add_edge("b", "a", capacity=1) + G.add_edge("b", "t", capacity=3) + # flow solution + # { + # "a": {"b": 1, "t": 1}, + # "b": {"a": 0, "t": 3}, + # "s": {"a": 2, "b": 2}, + # "t": {}, + # } + compare_flows_and_cuts(G, "s", "t", 4) + + def test_disconnected(self): + G = nx.Graph() + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + G.remove_node(1) + assert nx.maximum_flow_value(G, 0, 3) == 0 + # flow solution + # {0: {}, 2: {3: 0}, 3: {2: 0}} + compare_flows_and_cuts(G, 0, 3, 0) + + def test_source_target_not_in_graph(self): + G = nx.Graph() + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + G.remove_node(0) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 3) + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + G.remove_node(3) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 3) + + def test_source_target_coincide(self): + G = nx.Graph() + G.add_node(0) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 0) + + def test_multigraphs_raise(self): + G = nx.MultiGraph() + M = nx.MultiDiGraph() + G.add_edges_from([(0, 1), (1, 0)], capacity=True) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 0) + + +class TestMaxFlowMinCutInterface: + def setup_method(self): + G = nx.DiGraph() + G.add_edge("x", "a", capacity=3.0) + G.add_edge("x", "b", capacity=1.0) + G.add_edge("a", "c", capacity=3.0) + G.add_edge("b", "c", capacity=5.0) + G.add_edge("b", "d", capacity=4.0) + G.add_edge("d", "e", capacity=2.0) + G.add_edge("c", "y", capacity=2.0) + G.add_edge("e", "y", capacity=3.0) + self.G = G + H = nx.DiGraph() + H.add_edge(0, 1, capacity=1.0) + H.add_edge(1, 2, capacity=1.0) + self.H = H + + def test_flow_func_not_callable(self): + elements = ["this_should_be_callable", 10, {1, 2, 3}] + G = nx.Graph() + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + for flow_func in interface_funcs: + for element in elements: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 1, flow_func=element) + pytest.raises(nx.NetworkXError, flow_func, G, 0, 1, flow_func=element) + + def test_flow_func_parameters(self): + G = self.G + fv = 3.0 + for interface_func in interface_funcs: + for flow_func in flow_funcs: + errmsg = ( + f"Assertion failed in function: {flow_func.__name__} " + f"in interface {interface_func.__name__}" + ) + result = interface_func(G, "x", "y", flow_func=flow_func) + if interface_func in max_min_funcs: + result = result[0] + assert fv == result, errmsg + + def test_minimum_cut_no_cutoff(self): + G = self.G + pytest.raises( + nx.NetworkXError, + nx.minimum_cut, + G, + "x", + "y", + flow_func=preflow_push, + cutoff=1.0, + ) + pytest.raises( + nx.NetworkXError, + nx.minimum_cut_value, + G, + "x", + "y", + flow_func=preflow_push, + cutoff=1.0, + ) + + def test_kwargs(self): + G = self.H + fv = 1.0 + to_test = ( + (shortest_augmenting_path, {"two_phase": True}), + (preflow_push, {"global_relabel_freq": 5}), + ) + for interface_func in interface_funcs: + for flow_func, kwargs in to_test: + errmsg = ( + f"Assertion failed in function: {flow_func.__name__} " + f"in interface {interface_func.__name__}" + ) + result = interface_func(G, 0, 2, flow_func=flow_func, **kwargs) + if interface_func in max_min_funcs: + result = result[0] + assert fv == result, errmsg + + def test_kwargs_default_flow_func(self): + G = self.H + for interface_func in interface_funcs: + pytest.raises( + nx.NetworkXError, interface_func, G, 0, 1, global_relabel_freq=2 + ) + + def test_reusing_residual(self): + G = self.G + fv = 3.0 + s, t = "x", "y" + R = build_residual_network(G, "capacity") + for interface_func in interface_funcs: + for flow_func in flow_funcs: + errmsg = ( + f"Assertion failed in function: {flow_func.__name__} " + f"in interface {interface_func.__name__}" + ) + for i in range(3): + result = interface_func( + G, "x", "y", flow_func=flow_func, residual=R + ) + if interface_func in max_min_funcs: + result = result[0] + assert fv == result, errmsg + + +# Tests specific to one algorithm +def test_preflow_push_global_relabel_freq(): + G = nx.DiGraph() + G.add_edge(1, 2, capacity=1) + R = preflow_push(G, 1, 2, global_relabel_freq=None) + assert R.graph["flow_value"] == 1 + pytest.raises(nx.NetworkXError, preflow_push, G, 1, 2, global_relabel_freq=-1) + + +def test_preflow_push_makes_enough_space(): + # From ticket #1542 + G = nx.DiGraph() + nx.add_path(G, [0, 1, 3], capacity=1) + nx.add_path(G, [1, 2, 3], capacity=1) + R = preflow_push(G, 0, 3, value_only=False) + assert R.graph["flow_value"] == 1 + + +def test_shortest_augmenting_path_two_phase(): + k = 5 + p = 1000 + G = nx.DiGraph() + for i in range(k): + G.add_edge("s", (i, 0), capacity=1) + nx.add_path(G, ((i, j) for j in range(p)), capacity=1) + G.add_edge((i, p - 1), "t", capacity=1) + R = shortest_augmenting_path(G, "s", "t", two_phase=True) + assert R.graph["flow_value"] == k + R = shortest_augmenting_path(G, "s", "t", two_phase=False) + assert R.graph["flow_value"] == k + + +class TestCutoff: + def test_cutoff(self): + k = 5 + p = 1000 + G = nx.DiGraph() + for i in range(k): + G.add_edge("s", (i, 0), capacity=2) + nx.add_path(G, ((i, j) for j in range(p)), capacity=2) + G.add_edge((i, p - 1), "t", capacity=2) + R = shortest_augmenting_path(G, "s", "t", two_phase=True, cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = shortest_augmenting_path(G, "s", "t", two_phase=False, cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = edmonds_karp(G, "s", "t", cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = dinitz(G, "s", "t", cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = boykov_kolmogorov(G, "s", "t", cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + + def test_complete_graph_cutoff(self): + G = nx.complete_graph(5) + nx.set_edge_attributes(G, {(u, v): 1 for u, v in G.edges()}, "capacity") + for flow_func in [ + shortest_augmenting_path, + edmonds_karp, + dinitz, + boykov_kolmogorov, + ]: + for cutoff in [3, 2, 1]: + result = nx.maximum_flow_value( + G, 0, 4, flow_func=flow_func, cutoff=cutoff + ) + assert cutoff == result, f"cutoff error in {flow_func.__name__}" diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_networksimplex.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_networksimplex.py new file mode 100644 index 0000000000000000000000000000000000000000..5b3b5f6dd069e38b8be536cf4037a46da2366cc2 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/tests/test_networksimplex.py @@ -0,0 +1,387 @@ +import bz2 +import importlib.resources +import os +import pickle + +import pytest + +import networkx as nx + + +@pytest.fixture +def simple_flow_graph(): + G = nx.DiGraph() + G.add_node("a", demand=0) + G.add_node("b", demand=-5) + G.add_node("c", demand=50000000) + G.add_node("d", demand=-49999995) + G.add_edge("a", "b", weight=3, capacity=4) + G.add_edge("a", "c", weight=6, capacity=10) + G.add_edge("b", "d", weight=1, capacity=9) + G.add_edge("c", "d", weight=2, capacity=5) + return G + + +@pytest.fixture +def simple_no_flow_graph(): + G = nx.DiGraph() + G.add_node("s", demand=-5) + G.add_node("t", demand=5) + G.add_edge("s", "a", weight=1, capacity=3) + G.add_edge("a", "b", weight=3) + G.add_edge("a", "c", weight=-6) + G.add_edge("b", "d", weight=1) + G.add_edge("c", "d", weight=-2) + G.add_edge("d", "t", weight=1, capacity=3) + return G + + +def get_flowcost_from_flowdict(G, flowDict): + """Returns flow cost calculated from flow dictionary""" + flowCost = 0 + for u in flowDict: + for v in flowDict[u]: + flowCost += flowDict[u][v] * G[u][v]["weight"] + return flowCost + + +def test_infinite_demand_raise(simple_flow_graph): + G = simple_flow_graph + inf = float("inf") + nx.set_node_attributes(G, {"a": {"demand": inf}}) + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + + +def test_neg_infinite_demand_raise(simple_flow_graph): + G = simple_flow_graph + inf = float("inf") + nx.set_node_attributes(G, {"a": {"demand": -inf}}) + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + + +def test_infinite_weight_raise(simple_flow_graph): + G = simple_flow_graph + inf = float("inf") + nx.set_edge_attributes( + G, {("a", "b"): {"weight": inf}, ("b", "d"): {"weight": inf}} + ) + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + + +def test_nonzero_net_demand_raise(simple_flow_graph): + G = simple_flow_graph + nx.set_node_attributes(G, {"b": {"demand": -4}}) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + + +def test_negative_capacity_raise(simple_flow_graph): + G = simple_flow_graph + nx.set_edge_attributes(G, {("a", "b"): {"weight": 1}, ("b", "d"): {"capacity": -9}}) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + + +def test_no_flow_satisfying_demands(simple_no_flow_graph): + G = simple_no_flow_graph + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + + +def test_sum_demands_not_zero(simple_no_flow_graph): + G = simple_no_flow_graph + nx.set_node_attributes(G, {"t": {"demand": 4}}) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + + +def test_google_or_tools_example(): + """ + https://developers.google.com/optimization/flow/mincostflow + """ + G = nx.DiGraph() + start_nodes = [0, 0, 1, 1, 1, 2, 2, 3, 4] + end_nodes = [1, 2, 2, 3, 4, 3, 4, 4, 2] + capacities = [15, 8, 20, 4, 10, 15, 4, 20, 5] + unit_costs = [4, 4, 2, 2, 6, 1, 3, 2, 3] + supplies = [20, 0, 0, -5, -15] + answer = 150 + + for i in range(len(supplies)): + G.add_node(i, demand=(-1) * supplies[i]) # supplies are negative of demand + + for i in range(len(start_nodes)): + G.add_edge( + start_nodes[i], end_nodes[i], weight=unit_costs[i], capacity=capacities[i] + ) + + flowCost, flowDict = nx.network_simplex(G) + assert flowCost == answer + assert flowCost == get_flowcost_from_flowdict(G, flowDict) + + +def test_google_or_tools_example2(): + """ + https://developers.google.com/optimization/flow/mincostflow + """ + G = nx.DiGraph() + start_nodes = [0, 0, 1, 1, 1, 2, 2, 3, 4, 3] + end_nodes = [1, 2, 2, 3, 4, 3, 4, 4, 2, 5] + capacities = [15, 8, 20, 4, 10, 15, 4, 20, 5, 10] + unit_costs = [4, 4, 2, 2, 6, 1, 3, 2, 3, 4] + supplies = [23, 0, 0, -5, -15, -3] + answer = 183 + + for i in range(len(supplies)): + G.add_node(i, demand=(-1) * supplies[i]) # supplies are negative of demand + + for i in range(len(start_nodes)): + G.add_edge( + start_nodes[i], end_nodes[i], weight=unit_costs[i], capacity=capacities[i] + ) + + flowCost, flowDict = nx.network_simplex(G) + assert flowCost == answer + assert flowCost == get_flowcost_from_flowdict(G, flowDict) + + +def test_large(): + fname = ( + importlib.resources.files("networkx.algorithms.flow.tests") + / "netgen-2.gpickle.bz2" + ) + + with bz2.BZ2File(fname, "rb") as f: + G = pickle.load(f) + flowCost, flowDict = nx.network_simplex(G) + assert 6749969302 == flowCost + assert 6749969302 == nx.cost_of_flow(G, flowDict) + + +def test_simple_digraph(): + G = nx.DiGraph() + G.add_node("a", demand=-5) + G.add_node("d", demand=5) + G.add_edge("a", "b", weight=3, capacity=4) + G.add_edge("a", "c", weight=6, capacity=10) + G.add_edge("b", "d", weight=1, capacity=9) + G.add_edge("c", "d", weight=2, capacity=5) + flowCost, H = nx.network_simplex(G) + soln = {"a": {"b": 4, "c": 1}, "b": {"d": 4}, "c": {"d": 1}, "d": {}} + assert flowCost == 24 + assert nx.min_cost_flow_cost(G) == 24 + assert H == soln + + +def test_negcycle_infcap(): + G = nx.DiGraph() + G.add_node("s", demand=-5) + G.add_node("t", demand=5) + G.add_edge("s", "a", weight=1, capacity=3) + G.add_edge("a", "b", weight=3) + G.add_edge("c", "a", weight=-6) + G.add_edge("b", "d", weight=1) + G.add_edge("d", "c", weight=-2) + G.add_edge("d", "t", weight=1, capacity=3) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + + +def test_transshipment(): + G = nx.DiGraph() + G.add_node("a", demand=1) + G.add_node("b", demand=-2) + G.add_node("c", demand=-2) + G.add_node("d", demand=3) + G.add_node("e", demand=-4) + G.add_node("f", demand=-4) + G.add_node("g", demand=3) + G.add_node("h", demand=2) + G.add_node("r", demand=3) + G.add_edge("a", "c", weight=3) + G.add_edge("r", "a", weight=2) + G.add_edge("b", "a", weight=9) + G.add_edge("r", "c", weight=0) + G.add_edge("b", "r", weight=-6) + G.add_edge("c", "d", weight=5) + G.add_edge("e", "r", weight=4) + G.add_edge("e", "f", weight=3) + G.add_edge("h", "b", weight=4) + G.add_edge("f", "d", weight=7) + G.add_edge("f", "h", weight=12) + G.add_edge("g", "d", weight=12) + G.add_edge("f", "g", weight=-1) + G.add_edge("h", "g", weight=-10) + flowCost, H = nx.network_simplex(G) + soln = { + "a": {"c": 0}, + "b": {"a": 0, "r": 2}, + "c": {"d": 3}, + "d": {}, + "e": {"r": 3, "f": 1}, + "f": {"d": 0, "g": 3, "h": 2}, + "g": {"d": 0}, + "h": {"b": 0, "g": 0}, + "r": {"a": 1, "c": 1}, + } + assert flowCost == 41 + assert H == soln + + +def test_digraph1(): + # From Bradley, S. P., Hax, A. C. and Magnanti, T. L. Applied + # Mathematical Programming. Addison-Wesley, 1977. + G = nx.DiGraph() + G.add_node(1, demand=-20) + G.add_node(4, demand=5) + G.add_node(5, demand=15) + G.add_edges_from( + [ + (1, 2, {"capacity": 15, "weight": 4}), + (1, 3, {"capacity": 8, "weight": 4}), + (2, 3, {"weight": 2}), + (2, 4, {"capacity": 4, "weight": 2}), + (2, 5, {"capacity": 10, "weight": 6}), + (3, 4, {"capacity": 15, "weight": 1}), + (3, 5, {"capacity": 5, "weight": 3}), + (4, 5, {"weight": 2}), + (5, 3, {"capacity": 4, "weight": 1}), + ] + ) + flowCost, H = nx.network_simplex(G) + soln = { + 1: {2: 12, 3: 8}, + 2: {3: 8, 4: 4, 5: 0}, + 3: {4: 11, 5: 5}, + 4: {5: 10}, + 5: {3: 0}, + } + assert flowCost == 150 + assert nx.min_cost_flow_cost(G) == 150 + assert H == soln + + +def test_zero_capacity_edges(): + """Address issue raised in ticket #617 by arv.""" + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2, {"capacity": 1, "weight": 1}), + (1, 5, {"capacity": 1, "weight": 1}), + (2, 3, {"capacity": 0, "weight": 1}), + (2, 5, {"capacity": 1, "weight": 1}), + (5, 3, {"capacity": 2, "weight": 1}), + (5, 4, {"capacity": 0, "weight": 1}), + (3, 4, {"capacity": 2, "weight": 1}), + ] + ) + G.nodes[1]["demand"] = -1 + G.nodes[2]["demand"] = -1 + G.nodes[4]["demand"] = 2 + + flowCost, H = nx.network_simplex(G) + soln = {1: {2: 0, 5: 1}, 2: {3: 0, 5: 1}, 3: {4: 2}, 4: {}, 5: {3: 2, 4: 0}} + assert flowCost == 6 + assert nx.min_cost_flow_cost(G) == 6 + assert H == soln + + +def test_digon(): + """Check if digons are handled properly. Taken from ticket + #618 by arv.""" + nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})] + edges = [ + (1, 2, {"capacity": 3, "weight": 600000}), + (2, 1, {"capacity": 2, "weight": 0}), + (2, 3, {"capacity": 5, "weight": 714285}), + (3, 2, {"capacity": 2, "weight": 0}), + ] + G = nx.DiGraph(edges) + G.add_nodes_from(nodes) + flowCost, H = nx.network_simplex(G) + soln = {1: {2: 0}, 2: {1: 0, 3: 4}, 3: {2: 0}} + assert flowCost == 2857140 + + +def test_deadend(): + """Check if one-node cycles are handled properly. Taken from ticket + #2906 from @sshraven.""" + G = nx.DiGraph() + + G.add_nodes_from(range(5), demand=0) + G.nodes[4]["demand"] = -13 + G.nodes[3]["demand"] = 13 + + G.add_edges_from([(0, 2), (0, 3), (2, 1)], capacity=20, weight=0.1) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + + +def test_infinite_capacity_neg_digon(): + """An infinite capacity negative cost digon results in an unbounded + instance.""" + nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})] + edges = [ + (1, 2, {"weight": -600}), + (2, 1, {"weight": 0}), + (2, 3, {"capacity": 5, "weight": 714285}), + (3, 2, {"capacity": 2, "weight": 0}), + ] + G = nx.DiGraph(edges) + G.add_nodes_from(nodes) + pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G) + + +def test_multidigraph(): + """Multidigraphs are acceptable.""" + G = nx.MultiDiGraph() + G.add_weighted_edges_from([(1, 2, 1), (2, 3, 2)], weight="capacity") + flowCost, H = nx.network_simplex(G) + assert flowCost == 0 + assert H == {1: {2: {0: 0}}, 2: {3: {0: 0}}, 3: {}} + + +def test_negative_selfloops(): + """Negative selfloops should cause an exception if uncapacitated and + always be saturated otherwise. + """ + G = nx.DiGraph() + G.add_edge(1, 1, weight=-1) + pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G) + + G[1][1]["capacity"] = 2 + flowCost, H = nx.network_simplex(G) + assert flowCost == -2 + assert H == {1: {1: 2}} + + G = nx.MultiDiGraph() + G.add_edge(1, 1, "x", weight=-1) + G.add_edge(1, 1, "y", weight=1) + pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G) + + G[1][1]["x"]["capacity"] = 2 + flowCost, H = nx.network_simplex(G) + assert flowCost == -2 + assert H == {1: {1: {"x": 2, "y": 0}}} + + +def test_bone_shaped(): + # From #1283 + G = nx.DiGraph() + G.add_node(0, demand=-4) + G.add_node(1, demand=2) + G.add_node(2, demand=2) + G.add_node(3, demand=4) + G.add_node(4, demand=-2) + G.add_node(5, demand=-2) + G.add_edge(0, 1, capacity=4) + G.add_edge(0, 2, capacity=4) + G.add_edge(4, 3, capacity=4) + G.add_edge(5, 3, capacity=4) + G.add_edge(0, 3, capacity=0) + flowCost, H = nx.network_simplex(G) + assert flowCost == 0 + assert H == {0: {1: 2, 2: 2, 3: 0}, 1: {}, 2: {}, 3: {}, 4: {3: 2}, 5: {3: 2}} + + +def test_graphs_type_exceptions(): + G = nx.Graph() + pytest.raises(nx.NetworkXNotImplemented, nx.network_simplex, G) + G = nx.MultiGraph() + pytest.raises(nx.NetworkXNotImplemented, nx.network_simplex, G) + G = nx.DiGraph() + pytest.raises(nx.NetworkXError, nx.network_simplex, G) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/flow/utils.py b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/utils.py new file mode 100644 index 0000000000000000000000000000000000000000..03f1d10f75a9f2b3d80bdea8b4c086cebe1df966 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/flow/utils.py @@ -0,0 +1,189 @@ +""" +Utility classes and functions for network flow algorithms. +""" + +from collections import deque + +import networkx as nx + +__all__ = [ + "CurrentEdge", + "Level", + "GlobalRelabelThreshold", + "build_residual_network", + "detect_unboundedness", + "build_flow_dict", +] + + +class CurrentEdge: + """Mechanism for iterating over out-edges incident to a node in a circular + manner. StopIteration exception is raised when wraparound occurs. + """ + + __slots__ = ("_edges", "_it", "_curr") + + def __init__(self, edges): + self._edges = edges + if self._edges: + self._rewind() + + def get(self): + return self._curr + + def move_to_next(self): + try: + self._curr = next(self._it) + except StopIteration: + self._rewind() + raise + + def _rewind(self): + self._it = iter(self._edges.items()) + self._curr = next(self._it) + + +class Level: + """Active and inactive nodes in a level.""" + + __slots__ = ("active", "inactive") + + def __init__(self): + self.active = set() + self.inactive = set() + + +class GlobalRelabelThreshold: + """Measurement of work before the global relabeling heuristic should be + applied. + """ + + def __init__(self, n, m, freq): + self._threshold = (n + m) / freq if freq else float("inf") + self._work = 0 + + def add_work(self, work): + self._work += work + + def is_reached(self): + return self._work >= self._threshold + + def clear_work(self): + self._work = 0 + + +@nx._dispatchable(edge_attrs={"capacity": float("inf")}, returns_graph=True) +def build_residual_network(G, capacity): + """Build a residual network and initialize a zero flow. + + The residual network :samp:`R` from an input graph :samp:`G` has the + same nodes as :samp:`G`. :samp:`R` is a DiGraph that contains a pair + of edges :samp:`(u, v)` and :samp:`(v, u)` iff :samp:`(u, v)` is not a + self-loop, and at least one of :samp:`(u, v)` and :samp:`(v, u)` exists + in :samp:`G`. + + For each edge :samp:`(u, v)` in :samp:`R`, :samp:`R[u][v]['capacity']` + is equal to the capacity of :samp:`(u, v)` in :samp:`G` if it exists + in :samp:`G` or zero otherwise. If the capacity is infinite, + :samp:`R[u][v]['capacity']` will have a high arbitrary finite value + that does not affect the solution of the problem. This value is stored in + :samp:`R.graph['inf']`. For each edge :samp:`(u, v)` in :samp:`R`, + :samp:`R[u][v]['flow']` represents the flow function of :samp:`(u, v)` and + satisfies :samp:`R[u][v]['flow'] == -R[v][u]['flow']`. + + The flow value, defined as the total flow into :samp:`t`, the sink, is + stored in :samp:`R.graph['flow_value']`. If :samp:`cutoff` is not + specified, reachability to :samp:`t` using only edges :samp:`(u, v)` such + that :samp:`R[u][v]['flow'] < R[u][v]['capacity']` induces a minimum + :samp:`s`-:samp:`t` cut. + + """ + if G.is_multigraph(): + raise nx.NetworkXError("MultiGraph and MultiDiGraph not supported (yet).") + + R = nx.DiGraph() + R.__networkx_cache__ = None # Disable caching + R.add_nodes_from(G) + + inf = float("inf") + # Extract edges with positive capacities. Self loops excluded. + edge_list = [ + (u, v, attr) + for u, v, attr in G.edges(data=True) + if u != v and attr.get(capacity, inf) > 0 + ] + # Simulate infinity with three times the sum of the finite edge capacities + # or any positive value if the sum is zero. This allows the + # infinite-capacity edges to be distinguished for unboundedness detection + # and directly participate in residual capacity calculation. If the maximum + # flow is finite, these edges cannot appear in the minimum cut and thus + # guarantee correctness. Since the residual capacity of an + # infinite-capacity edge is always at least 2/3 of inf, while that of an + # finite-capacity edge is at most 1/3 of inf, if an operation moves more + # than 1/3 of inf units of flow to t, there must be an infinite-capacity + # s-t path in G. + inf = ( + 3 + * sum( + attr[capacity] + for u, v, attr in edge_list + if capacity in attr and attr[capacity] != inf + ) + or 1 + ) + if G.is_directed(): + for u, v, attr in edge_list: + r = min(attr.get(capacity, inf), inf) + if not R.has_edge(u, v): + # Both (u, v) and (v, u) must be present in the residual + # network. + R.add_edge(u, v, capacity=r) + R.add_edge(v, u, capacity=0) + else: + # The edge (u, v) was added when (v, u) was visited. + R[u][v]["capacity"] = r + else: + for u, v, attr in edge_list: + # Add a pair of edges with equal residual capacities. + r = min(attr.get(capacity, inf), inf) + R.add_edge(u, v, capacity=r) + R.add_edge(v, u, capacity=r) + + # Record the value simulating infinity. + R.graph["inf"] = inf + + return R + + +@nx._dispatchable( + graphs="R", + preserve_edge_attrs={"R": {"capacity": float("inf")}}, + preserve_graph_attrs=True, +) +def detect_unboundedness(R, s, t): + """Detect an infinite-capacity s-t path in R.""" + q = deque([s]) + seen = {s} + inf = R.graph["inf"] + while q: + u = q.popleft() + for v, attr in R[u].items(): + if attr["capacity"] == inf and v not in seen: + if v == t: + raise nx.NetworkXUnbounded( + "Infinite capacity path, flow unbounded above." + ) + seen.add(v) + q.append(v) + + +@nx._dispatchable(graphs={"G": 0, "R": 1}, preserve_edge_attrs={"R": {"flow": None}}) +def build_flow_dict(G, R): + """Build a flow dictionary from a residual network.""" + flow_dict = {} + for u in G: + flow_dict[u] = {v: 0 for v in G[u]} + flow_dict[u].update( + (v, attr["flow"]) for v, attr in R[u].items() if attr["flow"] > 0 + ) + return flow_dict diff --git 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a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/beamsearch.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/beamsearch.py new file mode 100644 index 0000000000000000000000000000000000000000..23fbe7bbb3f037eca4f7ede25b7edf6305356587 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/beamsearch.py @@ -0,0 +1,90 @@ +"""Basic algorithms for breadth-first searching the nodes of a graph.""" + +import networkx as nx + +__all__ = ["bfs_beam_edges"] + + +@nx._dispatchable +def bfs_beam_edges(G, source, value, width=None): + """Iterates over edges in a beam search. + + The beam search is a generalized breadth-first search in which only + the "best" *w* neighbors of the current node are enqueued, where *w* + is the beam width and "best" is an application-specific + heuristic. In general, a beam search with a small beam width might + not visit each node in the graph. + + .. note:: + + With the default value of ``width=None`` or `width` greater than the + maximum degree of the graph, this function equates to a slower + version of `~networkx.algorithms.traversal.breadth_first_search.bfs_edges`. + All nodes will be visited, though the order of the reported edges may + vary. In such cases, `value` has no effect - consider using `bfs_edges` + directly instead. + + Parameters + ---------- + G : NetworkX graph + + source : node + Starting node for the breadth-first search; this function + iterates over only those edges in the component reachable from + this node. + + value : function + A function that takes a node of the graph as input and returns a + real number indicating how "good" it is. A higher value means it + is more likely to be visited sooner during the search. When + visiting a new node, only the `width` neighbors with the highest + `value` are enqueued (in decreasing order of `value`). + + width : int (default = None) + The beam width for the search. This is the number of neighbors + (ordered by `value`) to enqueue when visiting each new node. + + Yields + ------ + edge + Edges in the beam search starting from `source`, given as a pair + of nodes. + + Examples + -------- + To give nodes with, for example, a higher centrality precedence + during the search, set the `value` function to return the centrality + value of the node: + + >>> G = nx.karate_club_graph() + >>> centrality = nx.eigenvector_centrality(G) + >>> list(nx.bfs_beam_edges(G, source=0, value=centrality.get, width=3)) + [(0, 2), (0, 1), (0, 8), (2, 32), (1, 13), (8, 33)] + """ + + if width is None: + width = len(G) + + def successors(v): + """Returns a list of the best neighbors of a node. + + `v` is a node in the graph `G`. + + The "best" neighbors are chosen according to the `value` + function (higher is better). Only the `width` best neighbors of + `v` are returned. + """ + # TODO The Python documentation states that for small values, it + # is better to use `heapq.nlargest`. We should determine the + # threshold at which its better to use `heapq.nlargest()` + # instead of `sorted()[:]` and apply that optimization here. + # + # If `width` is greater than the number of neighbors of `v`, all + # neighbors are returned by the semantics of slicing in + # Python. This occurs in the special case that the user did not + # specify a `width`: in this case all neighbors are always + # returned, so this is just a (slower) implementation of + # `bfs_edges(G, source)` but with a sorted enqueue step. + return iter(sorted(G.neighbors(v), key=value, reverse=True)[:width]) + + yield from nx.generic_bfs_edges(G, source, successors) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/breadth_first_search.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/breadth_first_search.py new file mode 100644 index 0000000000000000000000000000000000000000..899dc92b723665f88eb76dc90a0c1aee87dde1f4 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/breadth_first_search.py @@ -0,0 +1,575 @@ +"""Basic algorithms for breadth-first searching the nodes of a graph.""" + +from collections import deque + +import networkx as nx + +__all__ = [ + "bfs_edges", + "bfs_tree", + "bfs_predecessors", + "bfs_successors", + "descendants_at_distance", + "bfs_layers", + "bfs_labeled_edges", + "generic_bfs_edges", +] + + +@nx._dispatchable +def generic_bfs_edges(G, source, neighbors=None, depth_limit=None): + """Iterate over edges in a breadth-first search. + + The breadth-first search begins at `source` and enqueues the + neighbors of newly visited nodes specified by the `neighbors` + function. + + Parameters + ---------- + G : NetworkX graph + + source : node + Starting node for the breadth-first search; this function + iterates over only those edges in the component reachable from + this node. + + neighbors : function + A function that takes a newly visited node of the graph as input + and returns an *iterator* (not just a list) of nodes that are + neighbors of that node with custom ordering. If not specified, this is + just the ``G.neighbors`` method, but in general it can be any function + that returns an iterator over some or all of the neighbors of a + given node, in any order. + + depth_limit : int, optional(default=len(G)) + Specify the maximum search depth. + + Yields + ------ + edge + Edges in the breadth-first search starting from `source`. + + Examples + -------- + >>> G = nx.path_graph(7) + >>> list(nx.generic_bfs_edges(G, source=0)) + [(0, 1), (1, 2), (2, 3), (3, 4), (4, 5), (5, 6)] + >>> list(nx.generic_bfs_edges(G, source=2)) + [(2, 1), (2, 3), (1, 0), (3, 4), (4, 5), (5, 6)] + >>> list(nx.generic_bfs_edges(G, source=2, depth_limit=2)) + [(2, 1), (2, 3), (1, 0), (3, 4)] + + The `neighbors` param can be used to specify the visitation order of each + node's neighbors generically. In the following example, we modify the default + neighbor to return *odd* nodes first: + + >>> def odd_first(n): + ... return sorted(G.neighbors(n), key=lambda x: x % 2, reverse=True) + + >>> G = nx.star_graph(5) + >>> list(nx.generic_bfs_edges(G, source=0)) # Default neighbor ordering + [(0, 1), (0, 2), (0, 3), (0, 4), (0, 5)] + >>> list(nx.generic_bfs_edges(G, source=0, neighbors=odd_first)) + [(0, 1), (0, 3), (0, 5), (0, 2), (0, 4)] + + Notes + ----- + This implementation is from `PADS`_, which was in the public domain + when it was first accessed in July, 2004. The modifications + to allow depth limits are based on the Wikipedia article + "`Depth-limited-search`_". + + .. _PADS: http://www.ics.uci.edu/~eppstein/PADS/BFS.py + .. _Depth-limited-search: https://en.wikipedia.org/wiki/Depth-limited_search + """ + if neighbors is None: + neighbors = G.neighbors + if depth_limit is None: + depth_limit = len(G) + + seen = {source} + n = len(G) + depth = 0 + next_parents_children = [(source, neighbors(source))] + while next_parents_children and depth < depth_limit: + this_parents_children = next_parents_children + next_parents_children = [] + for parent, children in this_parents_children: + for child in children: + if child not in seen: + seen.add(child) + next_parents_children.append((child, neighbors(child))) + yield parent, child + if len(seen) == n: + return + depth += 1 + + +@nx._dispatchable +def bfs_edges(G, source, reverse=False, depth_limit=None, sort_neighbors=None): + """Iterate over edges in a breadth-first-search starting at source. + + Parameters + ---------- + G : NetworkX graph + + source : node + Specify starting node for breadth-first search; this function + iterates over only those edges in the component reachable from + this node. + + reverse : bool, optional + If True traverse a directed graph in the reverse direction + + depth_limit : int, optional(default=len(G)) + Specify the maximum search depth + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Yields + ------ + edge: 2-tuple of nodes + Yields edges resulting from the breadth-first search. + + Examples + -------- + To get the edges in a breadth-first search:: + + >>> G = nx.path_graph(3) + >>> list(nx.bfs_edges(G, 0)) + [(0, 1), (1, 2)] + >>> list(nx.bfs_edges(G, source=0, depth_limit=1)) + [(0, 1)] + + To get the nodes in a breadth-first search order:: + + >>> G = nx.path_graph(3) + >>> root = 2 + >>> edges = nx.bfs_edges(G, root) + >>> nodes = [root] + [v for u, v in edges] + >>> nodes + [2, 1, 0] + + Notes + ----- + The naming of this function is very similar to + :func:`~networkx.algorithms.traversal.edgebfs.edge_bfs`. The difference + is that ``edge_bfs`` yields edges even if they extend back to an already + explored node while this generator yields the edges of the tree that results + from a breadth-first-search (BFS) so no edges are reported if they extend + to already explored nodes. That means ``edge_bfs`` reports all edges while + ``bfs_edges`` only reports those traversed by a node-based BFS. Yet another + description is that ``bfs_edges`` reports the edges traversed during BFS + while ``edge_bfs`` reports all edges in the order they are explored. + + Based on the breadth-first search implementation in PADS [1]_ + by D. Eppstein, July 2004; with modifications to allow depth limits + as described in [2]_. + + References + ---------- + .. [1] http://www.ics.uci.edu/~eppstein/PADS/BFS.py. + .. [2] https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + bfs_tree + :func:`~networkx.algorithms.traversal.depth_first_search.dfs_edges` + :func:`~networkx.algorithms.traversal.edgebfs.edge_bfs` + + """ + if reverse and G.is_directed(): + successors = G.predecessors + else: + successors = G.neighbors + + if sort_neighbors is not None: + yield from generic_bfs_edges( + G, source, lambda node: iter(sort_neighbors(successors(node))), depth_limit + ) + else: + yield from generic_bfs_edges(G, source, successors, depth_limit) + + +@nx._dispatchable(returns_graph=True) +def bfs_tree(G, source, reverse=False, depth_limit=None, sort_neighbors=None): + """Returns an oriented tree constructed from of a breadth-first-search + starting at source. + + Parameters + ---------- + G : NetworkX graph + + source : node + Specify starting node for breadth-first search + + reverse : bool, optional + If True traverse a directed graph in the reverse direction + + depth_limit : int, optional(default=len(G)) + Specify the maximum search depth + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + T: NetworkX DiGraph + An oriented tree + + Examples + -------- + >>> G = nx.path_graph(3) + >>> list(nx.bfs_tree(G, 1).edges()) + [(1, 0), (1, 2)] + >>> H = nx.Graph() + >>> nx.add_path(H, [0, 1, 2, 3, 4, 5, 6]) + >>> nx.add_path(H, [2, 7, 8, 9, 10]) + >>> sorted(list(nx.bfs_tree(H, source=3, depth_limit=3).edges())) + [(1, 0), (2, 1), (2, 7), (3, 2), (3, 4), (4, 5), (5, 6), (7, 8)] + + + Notes + ----- + Based on http://www.ics.uci.edu/~eppstein/PADS/BFS.py + by D. Eppstein, July 2004. The modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited-search`_". + + .. _Depth-limited-search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + dfs_tree + bfs_edges + edge_bfs + """ + T = nx.DiGraph() + T.add_node(source) + edges_gen = bfs_edges( + G, + source, + reverse=reverse, + depth_limit=depth_limit, + sort_neighbors=sort_neighbors, + ) + T.add_edges_from(edges_gen) + return T + + +@nx._dispatchable +def bfs_predecessors(G, source, depth_limit=None, sort_neighbors=None): + """Returns an iterator of predecessors in breadth-first-search from source. + + Parameters + ---------- + G : NetworkX graph + + source : node + Specify starting node for breadth-first search + + depth_limit : int, optional(default=len(G)) + Specify the maximum search depth + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + pred: iterator + (node, predecessor) iterator where `predecessor` is the predecessor of + `node` in a breadth first search starting from `source`. + + Examples + -------- + >>> G = nx.path_graph(3) + >>> dict(nx.bfs_predecessors(G, 0)) + {1: 0, 2: 1} + >>> H = nx.Graph() + >>> H.add_edges_from([(0, 1), (0, 2), (1, 3), (1, 4), (2, 5), (2, 6)]) + >>> dict(nx.bfs_predecessors(H, 0)) + {1: 0, 2: 0, 3: 1, 4: 1, 5: 2, 6: 2} + >>> M = nx.Graph() + >>> nx.add_path(M, [0, 1, 2, 3, 4, 5, 6]) + >>> nx.add_path(M, [2, 7, 8, 9, 10]) + >>> sorted(nx.bfs_predecessors(M, source=1, depth_limit=3)) + [(0, 1), (2, 1), (3, 2), (4, 3), (7, 2), (8, 7)] + >>> N = nx.DiGraph() + >>> nx.add_path(N, [0, 1, 2, 3, 4, 7]) + >>> nx.add_path(N, [3, 5, 6, 7]) + >>> sorted(nx.bfs_predecessors(N, source=2)) + [(3, 2), (4, 3), (5, 3), (6, 5), (7, 4)] + + Notes + ----- + Based on http://www.ics.uci.edu/~eppstein/PADS/BFS.py + by D. Eppstein, July 2004. The modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited-search`_". + + .. _Depth-limited-search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + bfs_tree + bfs_edges + edge_bfs + """ + for s, t in bfs_edges( + G, source, depth_limit=depth_limit, sort_neighbors=sort_neighbors + ): + yield (t, s) + + +@nx._dispatchable +def bfs_successors(G, source, depth_limit=None, sort_neighbors=None): + """Returns an iterator of successors in breadth-first-search from source. + + Parameters + ---------- + G : NetworkX graph + + source : node + Specify starting node for breadth-first search + + depth_limit : int, optional(default=len(G)) + Specify the maximum search depth + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + succ: iterator + (node, successors) iterator where `successors` is the non-empty list of + successors of `node` in a breadth first search from `source`. + To appear in the iterator, `node` must have successors. + + Examples + -------- + >>> G = nx.path_graph(3) + >>> dict(nx.bfs_successors(G, 0)) + {0: [1], 1: [2]} + >>> H = nx.Graph() + >>> H.add_edges_from([(0, 1), (0, 2), (1, 3), (1, 4), (2, 5), (2, 6)]) + >>> dict(nx.bfs_successors(H, 0)) + {0: [1, 2], 1: [3, 4], 2: [5, 6]} + >>> G = nx.Graph() + >>> nx.add_path(G, [0, 1, 2, 3, 4, 5, 6]) + >>> nx.add_path(G, [2, 7, 8, 9, 10]) + >>> dict(nx.bfs_successors(G, source=1, depth_limit=3)) + {1: [0, 2], 2: [3, 7], 3: [4], 7: [8]} + >>> G = nx.DiGraph() + >>> nx.add_path(G, [0, 1, 2, 3, 4, 5]) + >>> dict(nx.bfs_successors(G, source=3)) + {3: [4], 4: [5]} + + Notes + ----- + Based on http://www.ics.uci.edu/~eppstein/PADS/BFS.py + by D. Eppstein, July 2004.The modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited-search`_". + + .. _Depth-limited-search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + bfs_tree + bfs_edges + edge_bfs + """ + parent = source + children = [] + for p, c in bfs_edges( + G, source, depth_limit=depth_limit, sort_neighbors=sort_neighbors + ): + if p == parent: + children.append(c) + continue + yield (parent, children) + children = [c] + parent = p + yield (parent, children) + + +@nx._dispatchable +def bfs_layers(G, sources): + """Returns an iterator of all the layers in breadth-first search traversal. + + Parameters + ---------- + G : NetworkX graph + A graph over which to find the layers using breadth-first search. + + sources : node in `G` or list of nodes in `G` + Specify starting nodes for single source or multiple sources breadth-first search + + Yields + ------ + layer: list of nodes + Yields list of nodes at the same distance from sources + + Examples + -------- + >>> G = nx.path_graph(5) + >>> dict(enumerate(nx.bfs_layers(G, [0, 4]))) + {0: [0, 4], 1: [1, 3], 2: [2]} + >>> H = nx.Graph() + >>> H.add_edges_from([(0, 1), (0, 2), (1, 3), (1, 4), (2, 5), (2, 6)]) + >>> dict(enumerate(nx.bfs_layers(H, [1]))) + {0: [1], 1: [0, 3, 4], 2: [2], 3: [5, 6]} + >>> dict(enumerate(nx.bfs_layers(H, [1, 6]))) + {0: [1, 6], 1: [0, 3, 4, 2], 2: [5]} + """ + if sources in G: + sources = [sources] + + current_layer = list(sources) + visited = set(sources) + + for source in current_layer: + if source not in G: + raise nx.NetworkXError(f"The node {source} is not in the graph.") + + # this is basically BFS, except that the current layer only stores the nodes at + # same distance from sources at each iteration + while current_layer: + yield current_layer + next_layer = [] + for node in current_layer: + for child in G[node]: + if child not in visited: + visited.add(child) + next_layer.append(child) + current_layer = next_layer + + +REVERSE_EDGE = "reverse" +TREE_EDGE = "tree" +FORWARD_EDGE = "forward" +LEVEL_EDGE = "level" + + +@nx._dispatchable +def bfs_labeled_edges(G, sources): + """Iterate over edges in a breadth-first search (BFS) labeled by type. + + We generate triple of the form (*u*, *v*, *d*), where (*u*, *v*) is the + edge being explored in the breadth-first search and *d* is one of the + strings 'tree', 'forward', 'level', or 'reverse'. A 'tree' edge is one in + which *v* is first discovered and placed into the layer below *u*. A + 'forward' edge is one in which *u* is on the layer above *v* and *v* has + already been discovered. A 'level' edge is one in which both *u* and *v* + occur on the same layer. A 'reverse' edge is one in which *u* is on a layer + below *v*. + + We emit each edge exactly once. In an undirected graph, 'reverse' edges do + not occur, because each is discovered either as a 'tree' or 'forward' edge. + + Parameters + ---------- + G : NetworkX graph + A graph over which to find the layers using breadth-first search. + + sources : node in `G` or list of nodes in `G` + Starting nodes for single source or multiple sources breadth-first search + + Yields + ------ + edges: generator + A generator of triples (*u*, *v*, *d*) where (*u*, *v*) is the edge being + explored and *d* is described above. + + Examples + -------- + >>> G = nx.cycle_graph(4, create_using=nx.DiGraph) + >>> list(nx.bfs_labeled_edges(G, 0)) + [(0, 1, 'tree'), (1, 2, 'tree'), (2, 3, 'tree'), (3, 0, 'reverse')] + >>> G = nx.complete_graph(3) + >>> list(nx.bfs_labeled_edges(G, 0)) + [(0, 1, 'tree'), (0, 2, 'tree'), (1, 2, 'level')] + >>> list(nx.bfs_labeled_edges(G, [0, 1])) + [(0, 1, 'level'), (0, 2, 'tree'), (1, 2, 'forward')] + """ + if sources in G: + sources = [sources] + + neighbors = G._adj + directed = G.is_directed() + visited = set() + visit = visited.discard if directed else visited.add + # We use visited in a negative sense, so the visited set stays empty for the + # directed case and level edges are reported on their first occurrence in + # the undirected case. Note our use of visited.discard -- this is built-in + # thus somewhat faster than a python-defined def nop(x): pass + depth = {s: 0 for s in sources} + queue = deque(depth.items()) + push = queue.append + pop = queue.popleft + while queue: + u, du = pop() + for v in neighbors[u]: + if v not in depth: + depth[v] = dv = du + 1 + push((v, dv)) + yield u, v, TREE_EDGE + else: + dv = depth[v] + if du == dv: + if v not in visited: + yield u, v, LEVEL_EDGE + elif du < dv: + yield u, v, FORWARD_EDGE + elif directed: + yield u, v, REVERSE_EDGE + visit(u) + + +@nx._dispatchable +def descendants_at_distance(G, source, distance): + """Returns all nodes at a fixed `distance` from `source` in `G`. + + Parameters + ---------- + G : NetworkX graph + A graph + source : node in `G` + distance : the distance of the wanted nodes from `source` + + Returns + ------- + set() + The descendants of `source` in `G` at the given `distance` from `source` + + Examples + -------- + >>> G = nx.path_graph(5) + >>> nx.descendants_at_distance(G, 2, 2) + {0, 4} + >>> H = nx.DiGraph() + >>> H.add_edges_from([(0, 1), (0, 2), (1, 3), (1, 4), (2, 5), (2, 6)]) + >>> nx.descendants_at_distance(H, 0, 2) + {3, 4, 5, 6} + >>> nx.descendants_at_distance(H, 5, 0) + {5} + >>> nx.descendants_at_distance(H, 5, 1) + set() + """ + if source not in G: + raise nx.NetworkXError(f"The node {source} is not in the graph.") + + bfs_generator = nx.bfs_layers(G, source) + for i, layer in enumerate(bfs_generator): + if i == distance: + return set(layer) + return set() diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/depth_first_search.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/depth_first_search.py new file mode 100644 index 0000000000000000000000000000000000000000..5bac5ecfd1cbefcba5707cac2885ef32987ee98b --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/depth_first_search.py @@ -0,0 +1,529 @@ +"""Basic algorithms for depth-first searching the nodes of a graph.""" + +from collections import defaultdict + +import networkx as nx + +__all__ = [ + "dfs_edges", + "dfs_tree", + "dfs_predecessors", + "dfs_successors", + "dfs_preorder_nodes", + "dfs_postorder_nodes", + "dfs_labeled_edges", +] + + +@nx._dispatchable +def dfs_edges(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Iterate over edges in a depth-first-search (DFS). + + Perform a depth-first-search over the nodes of `G` and yield + the edges in order. This may not generate all edges in `G` + (see `~networkx.algorithms.traversal.edgedfs.edge_dfs`). + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search and yield edges in + the component reachable from source. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Yields + ------ + edge: 2-tuple of nodes + Yields edges resulting from the depth-first-search. + + Examples + -------- + >>> G = nx.path_graph(5) + >>> list(nx.dfs_edges(G, source=0)) + [(0, 1), (1, 2), (2, 3), (3, 4)] + >>> list(nx.dfs_edges(G, source=0, depth_limit=2)) + [(0, 1), (1, 2)] + + Notes + ----- + If a source is not specified then a source is chosen arbitrarily and + repeatedly until all components in the graph are searched. + + The implementation of this function is adapted from David Eppstein's + depth-first search function in PADS [1]_, with modifications + to allow depth limits based on the Wikipedia article + "Depth-limited search" [2]_. + + See Also + -------- + dfs_preorder_nodes + dfs_postorder_nodes + dfs_labeled_edges + :func:`~networkx.algorithms.traversal.edgedfs.edge_dfs` + :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_edges` + + References + ---------- + .. [1] http://www.ics.uci.edu/~eppstein/PADS + .. [2] https://en.wikipedia.org/wiki/Depth-limited_search + """ + if source is None: + # edges for all components + nodes = G + else: + # edges for components with source + nodes = [source] + if depth_limit is None: + depth_limit = len(G) + + get_children = ( + G.neighbors + if sort_neighbors is None + else lambda n: iter(sort_neighbors(G.neighbors(n))) + ) + + visited = set() + for start in nodes: + if start in visited: + continue + visited.add(start) + stack = [(start, get_children(start))] + depth_now = 1 + while stack: + parent, children = stack[-1] + for child in children: + if child not in visited: + yield parent, child + visited.add(child) + if depth_now < depth_limit: + stack.append((child, get_children(child))) + depth_now += 1 + break + else: + stack.pop() + depth_now -= 1 + + +@nx._dispatchable(returns_graph=True) +def dfs_tree(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Returns oriented tree constructed from a depth-first-search from source. + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + T : NetworkX DiGraph + An oriented tree + + Examples + -------- + >>> G = nx.path_graph(5) + >>> T = nx.dfs_tree(G, source=0, depth_limit=2) + >>> list(T.edges()) + [(0, 1), (1, 2)] + >>> T = nx.dfs_tree(G, source=0) + >>> list(T.edges()) + [(0, 1), (1, 2), (2, 3), (3, 4)] + + See Also + -------- + dfs_preorder_nodes + dfs_postorder_nodes + dfs_labeled_edges + :func:`~networkx.algorithms.traversal.edgedfs.edge_dfs` + :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_tree` + """ + T = nx.DiGraph() + if source is None: + T.add_nodes_from(G) + else: + T.add_node(source) + T.add_edges_from(dfs_edges(G, source, depth_limit, sort_neighbors=sort_neighbors)) + return T + + +@nx._dispatchable +def dfs_predecessors(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Returns dictionary of predecessors in depth-first-search from source. + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search. + Note that you will get predecessors for all nodes in the + component containing `source`. This input only specifies + where the DFS starts. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + pred: dict + A dictionary with nodes as keys and predecessor nodes as values. + + Examples + -------- + >>> G = nx.path_graph(4) + >>> nx.dfs_predecessors(G, source=0) + {1: 0, 2: 1, 3: 2} + >>> nx.dfs_predecessors(G, source=0, depth_limit=2) + {1: 0, 2: 1} + + Notes + ----- + If a source is not specified then a source is chosen arbitrarily and + repeatedly until all components in the graph are searched. + + The implementation of this function is adapted from David Eppstein's + depth-first search function in `PADS`_, with modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited search`_". + + .. _PADS: http://www.ics.uci.edu/~eppstein/PADS + .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + dfs_preorder_nodes + dfs_postorder_nodes + dfs_labeled_edges + :func:`~networkx.algorithms.traversal.edgedfs.edge_dfs` + :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_tree` + """ + return { + t: s + for s, t in dfs_edges(G, source, depth_limit, sort_neighbors=sort_neighbors) + } + + +@nx._dispatchable +def dfs_successors(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Returns dictionary of successors in depth-first-search from source. + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search. + Note that you will get successors for all nodes in the + component containing `source`. This input only specifies + where the DFS starts. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + succ: dict + A dictionary with nodes as keys and list of successor nodes as values. + + Examples + -------- + >>> G = nx.path_graph(5) + >>> nx.dfs_successors(G, source=0) + {0: [1], 1: [2], 2: [3], 3: [4]} + >>> nx.dfs_successors(G, source=0, depth_limit=2) + {0: [1], 1: [2]} + + Notes + ----- + If a source is not specified then a source is chosen arbitrarily and + repeatedly until all components in the graph are searched. + + The implementation of this function is adapted from David Eppstein's + depth-first search function in `PADS`_, with modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited search`_". + + .. _PADS: http://www.ics.uci.edu/~eppstein/PADS + .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + dfs_preorder_nodes + dfs_postorder_nodes + dfs_labeled_edges + :func:`~networkx.algorithms.traversal.edgedfs.edge_dfs` + :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_tree` + """ + d = defaultdict(list) + for s, t in dfs_edges( + G, + source=source, + depth_limit=depth_limit, + sort_neighbors=sort_neighbors, + ): + d[s].append(t) + return dict(d) + + +@nx._dispatchable +def dfs_postorder_nodes(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Generate nodes in a depth-first-search post-ordering starting at source. + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + nodes: generator + A generator of nodes in a depth-first-search post-ordering. + + Examples + -------- + >>> G = nx.path_graph(5) + >>> list(nx.dfs_postorder_nodes(G, source=0)) + [4, 3, 2, 1, 0] + >>> list(nx.dfs_postorder_nodes(G, source=0, depth_limit=2)) + [1, 0] + + Notes + ----- + If a source is not specified then a source is chosen arbitrarily and + repeatedly until all components in the graph are searched. + + The implementation of this function is adapted from David Eppstein's + depth-first search function in `PADS`_, with modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited search`_". + + .. _PADS: http://www.ics.uci.edu/~eppstein/PADS + .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + dfs_edges + dfs_preorder_nodes + dfs_labeled_edges + :func:`~networkx.algorithms.traversal.edgedfs.edge_dfs` + :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_tree` + """ + edges = nx.dfs_labeled_edges( + G, source=source, depth_limit=depth_limit, sort_neighbors=sort_neighbors + ) + return (v for u, v, d in edges if d == "reverse") + + +@nx._dispatchable +def dfs_preorder_nodes(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Generate nodes in a depth-first-search pre-ordering starting at source. + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search and return nodes in + the component reachable from source. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + nodes: generator + A generator of nodes in a depth-first-search pre-ordering. + + Examples + -------- + >>> G = nx.path_graph(5) + >>> list(nx.dfs_preorder_nodes(G, source=0)) + [0, 1, 2, 3, 4] + >>> list(nx.dfs_preorder_nodes(G, source=0, depth_limit=2)) + [0, 1, 2] + + Notes + ----- + If a source is not specified then a source is chosen arbitrarily and + repeatedly until all components in the graph are searched. + + The implementation of this function is adapted from David Eppstein's + depth-first search function in `PADS`_, with modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited search`_". + + .. _PADS: http://www.ics.uci.edu/~eppstein/PADS + .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + dfs_edges + dfs_postorder_nodes + dfs_labeled_edges + :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_edges` + """ + edges = nx.dfs_labeled_edges( + G, source=source, depth_limit=depth_limit, sort_neighbors=sort_neighbors + ) + return (v for u, v, d in edges if d == "forward") + + +@nx._dispatchable +def dfs_labeled_edges(G, source=None, depth_limit=None, *, sort_neighbors=None): + """Iterate over edges in a depth-first-search (DFS) labeled by type. + + Parameters + ---------- + G : NetworkX graph + + source : node, optional + Specify starting node for depth-first search and return edges in + the component reachable from source. + + depth_limit : int, optional (default=len(G)) + Specify the maximum search depth. + + sort_neighbors : function (default=None) + A function that takes an iterator over nodes as the input, and + returns an iterable of the same nodes with a custom ordering. + For example, `sorted` will sort the nodes in increasing order. + + Returns + ------- + edges: generator + A generator of triples of the form (*u*, *v*, *d*), where (*u*, + *v*) is the edge being explored in the depth-first search and *d* + is one of the strings 'forward', 'nontree', 'reverse', or 'reverse-depth_limit'. + A 'forward' edge is one in which *u* has been visited but *v* has + not. A 'nontree' edge is one in which both *u* and *v* have been + visited but the edge is not in the DFS tree. A 'reverse' edge is + one in which both *u* and *v* have been visited and the edge is in + the DFS tree. When the `depth_limit` is reached via a 'forward' edge, + a 'reverse' edge is immediately generated rather than the subtree + being explored. To indicate this flavor of 'reverse' edge, the string + yielded is 'reverse-depth_limit'. + + Examples + -------- + + The labels reveal the complete transcript of the depth-first search + algorithm in more detail than, for example, :func:`dfs_edges`:: + + >>> from pprint import pprint + >>> + >>> G = nx.DiGraph([(0, 1), (1, 2), (2, 1)]) + >>> pprint(list(nx.dfs_labeled_edges(G, source=0))) + [(0, 0, 'forward'), + (0, 1, 'forward'), + (1, 2, 'forward'), + (2, 1, 'nontree'), + (1, 2, 'reverse'), + (0, 1, 'reverse'), + (0, 0, 'reverse')] + + Notes + ----- + If a source is not specified then a source is chosen arbitrarily and + repeatedly until all components in the graph are searched. + + The implementation of this function is adapted from David Eppstein's + depth-first search function in `PADS`_, with modifications + to allow depth limits based on the Wikipedia article + "`Depth-limited search`_". + + .. _PADS: http://www.ics.uci.edu/~eppstein/PADS + .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search + + See Also + -------- + dfs_edges + dfs_preorder_nodes + dfs_postorder_nodes + """ + # Based on http://www.ics.uci.edu/~eppstein/PADS/DFS.py + # by D. Eppstein, July 2004. + if source is None: + # edges for all components + nodes = G + else: + # edges for components with source + nodes = [source] + if depth_limit is None: + depth_limit = len(G) + + get_children = ( + G.neighbors + if sort_neighbors is None + else lambda n: iter(sort_neighbors(G.neighbors(n))) + ) + + visited = set() + for start in nodes: + if start in visited: + continue + yield start, start, "forward" + visited.add(start) + stack = [(start, get_children(start))] + depth_now = 1 + while stack: + parent, children = stack[-1] + for child in children: + if child in visited: + yield parent, child, "nontree" + else: + yield parent, child, "forward" + visited.add(child) + if depth_now < depth_limit: + stack.append((child, iter(get_children(child)))) + depth_now += 1 + break + else: + yield parent, child, "reverse-depth_limit" + else: + stack.pop() + depth_now -= 1 + if stack: + yield stack[-1][0], parent, "reverse" + yield start, start, "reverse" diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/edgebfs.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/edgebfs.py new file mode 100644 index 0000000000000000000000000000000000000000..6320ddc2a683187136103dd1cb18036ae3088d03 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/edgebfs.py @@ -0,0 +1,178 @@ +""" +============================= +Breadth First Search on Edges +============================= + +Algorithms for a breadth-first traversal of edges in a graph. + +""" + +from collections import deque + +import networkx as nx + +FORWARD = "forward" +REVERSE = "reverse" + +__all__ = ["edge_bfs"] + + +@nx._dispatchable +def edge_bfs(G, source=None, orientation=None): + """A directed, breadth-first-search of edges in `G`, beginning at `source`. + + Yield the edges of G in a breadth-first-search order continuing until + all edges are generated. + + Parameters + ---------- + G : graph + A directed/undirected graph/multigraph. + + source : node, list of nodes + The node from which the traversal begins. If None, then a source + is chosen arbitrarily and repeatedly until all edges from each node in + the graph are searched. + + orientation : None | 'original' | 'reverse' | 'ignore' (default: None) + For directed graphs and directed multigraphs, edge traversals need not + respect the original orientation of the edges. + When set to 'reverse' every edge is traversed in the reverse direction. + When set to 'ignore', every edge is treated as undirected. + When set to 'original', every edge is treated as directed. + In all three cases, the yielded edge tuples add a last entry to + indicate the direction in which that edge was traversed. + If orientation is None, the yielded edge has no direction indicated. + The direction is respected, but not reported. + + Yields + ------ + edge : directed edge + A directed edge indicating the path taken by the breadth-first-search. + For graphs, `edge` is of the form `(u, v)` where `u` and `v` + are the tail and head of the edge as determined by the traversal. + For multigraphs, `edge` is of the form `(u, v, key)`, where `key` is + the key of the edge. When the graph is directed, then `u` and `v` + are always in the order of the actual directed edge. + If orientation is not None then the edge tuple is extended to include + the direction of traversal ('forward' or 'reverse') on that edge. + + Examples + -------- + >>> nodes = [0, 1, 2, 3] + >>> edges = [(0, 1), (1, 0), (1, 0), (2, 0), (2, 1), (3, 1)] + + >>> list(nx.edge_bfs(nx.Graph(edges), nodes)) + [(0, 1), (0, 2), (1, 2), (1, 3)] + + >>> list(nx.edge_bfs(nx.DiGraph(edges), nodes)) + [(0, 1), (1, 0), (2, 0), (2, 1), (3, 1)] + + >>> list(nx.edge_bfs(nx.MultiGraph(edges), nodes)) + [(0, 1, 0), (0, 1, 1), (0, 1, 2), (0, 2, 0), (1, 2, 0), (1, 3, 0)] + + >>> list(nx.edge_bfs(nx.MultiDiGraph(edges), nodes)) + [(0, 1, 0), (1, 0, 0), (1, 0, 1), (2, 0, 0), (2, 1, 0), (3, 1, 0)] + + >>> list(nx.edge_bfs(nx.DiGraph(edges), nodes, orientation="ignore")) + [(0, 1, 'forward'), (1, 0, 'reverse'), (2, 0, 'reverse'), (2, 1, 'reverse'), (3, 1, 'reverse')] + + >>> list(nx.edge_bfs(nx.MultiDiGraph(edges), nodes, orientation="ignore")) + [(0, 1, 0, 'forward'), (1, 0, 0, 'reverse'), (1, 0, 1, 'reverse'), (2, 0, 0, 'reverse'), (2, 1, 0, 'reverse'), (3, 1, 0, 'reverse')] + + Notes + ----- + The goal of this function is to visit edges. It differs from the more + familiar breadth-first-search of nodes, as provided by + :func:`networkx.algorithms.traversal.breadth_first_search.bfs_edges`, in + that it does not stop once every node has been visited. In a directed graph + with edges [(0, 1), (1, 2), (2, 1)], the edge (2, 1) would not be visited + if not for the functionality provided by this function. + + The naming of this function is very similar to bfs_edges. The difference + is that 'edge_bfs' yields edges even if they extend back to an already + explored node while 'bfs_edges' yields the edges of the tree that results + from a breadth-first-search (BFS) so no edges are reported if they extend + to already explored nodes. That means 'edge_bfs' reports all edges while + 'bfs_edges' only report those traversed by a node-based BFS. Yet another + description is that 'bfs_edges' reports the edges traversed during BFS + while 'edge_bfs' reports all edges in the order they are explored. + + See Also + -------- + bfs_edges + bfs_tree + edge_dfs + + """ + nodes = list(G.nbunch_iter(source)) + if not nodes: + return + + directed = G.is_directed() + kwds = {"data": False} + if G.is_multigraph() is True: + kwds["keys"] = True + + # set up edge lookup + if orientation is None: + + def edges_from(node): + return iter(G.edges(node, **kwds)) + + elif not directed or orientation == "original": + + def edges_from(node): + for e in G.edges(node, **kwds): + yield e + (FORWARD,) + + elif orientation == "reverse": + + def edges_from(node): + for e in G.in_edges(node, **kwds): + yield e + (REVERSE,) + + elif orientation == "ignore": + + def edges_from(node): + for e in G.edges(node, **kwds): + yield e + (FORWARD,) + for e in G.in_edges(node, **kwds): + yield e + (REVERSE,) + + else: + raise nx.NetworkXError("invalid orientation argument.") + + if directed: + neighbors = G.successors + + def edge_id(edge): + # remove direction indicator + return edge[:-1] if orientation is not None else edge + + else: + neighbors = G.neighbors + + def edge_id(edge): + return (frozenset(edge[:2]),) + edge[2:] + + check_reverse = directed and orientation in ("reverse", "ignore") + + # start BFS + visited_nodes = set(nodes) + visited_edges = set() + queue = deque([(n, edges_from(n)) for n in nodes]) + while queue: + parent, children_edges = queue.popleft() + for edge in children_edges: + if check_reverse and edge[-1] == REVERSE: + child = edge[0] + else: + child = edge[1] + if child not in visited_nodes: + visited_nodes.add(child) + queue.append((child, edges_from(child))) + edgeid = edge_id(edge) + if edgeid not in visited_edges: + visited_edges.add(edgeid) + yield edge diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/edgedfs.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/edgedfs.py new file mode 100644 index 0000000000000000000000000000000000000000..8f657f39fdd8a24660772d7cc3cef0f641ed61c5 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/edgedfs.py @@ -0,0 +1,176 @@ +""" +=========================== +Depth First Search on Edges +=========================== + +Algorithms for a depth-first traversal of edges in a graph. + +""" + +import networkx as nx + +FORWARD = "forward" +REVERSE = "reverse" + +__all__ = ["edge_dfs"] + + +@nx._dispatchable +def edge_dfs(G, source=None, orientation=None): + """A directed, depth-first-search of edges in `G`, beginning at `source`. + + Yield the edges of G in a depth-first-search order continuing until + all edges are generated. + + Parameters + ---------- + G : graph + A directed/undirected graph/multigraph. + + source : node, list of nodes + The node from which the traversal begins. If None, then a source + is chosen arbitrarily and repeatedly until all edges from each node in + the graph are searched. + + orientation : None | 'original' | 'reverse' | 'ignore' (default: None) + For directed graphs and directed multigraphs, edge traversals need not + respect the original orientation of the edges. + When set to 'reverse' every edge is traversed in the reverse direction. + When set to 'ignore', every edge is treated as undirected. + When set to 'original', every edge is treated as directed. + In all three cases, the yielded edge tuples add a last entry to + indicate the direction in which that edge was traversed. + If orientation is None, the yielded edge has no direction indicated. + The direction is respected, but not reported. + + Yields + ------ + edge : directed edge + A directed edge indicating the path taken by the depth-first traversal. + For graphs, `edge` is of the form `(u, v)` where `u` and `v` + are the tail and head of the edge as determined by the traversal. + For multigraphs, `edge` is of the form `(u, v, key)`, where `key` is + the key of the edge. When the graph is directed, then `u` and `v` + are always in the order of the actual directed edge. + If orientation is not None then the edge tuple is extended to include + the direction of traversal ('forward' or 'reverse') on that edge. + + Examples + -------- + >>> nodes = [0, 1, 2, 3] + >>> edges = [(0, 1), (1, 0), (1, 0), (2, 1), (3, 1)] + + >>> list(nx.edge_dfs(nx.Graph(edges), nodes)) + [(0, 1), (1, 2), (1, 3)] + + >>> list(nx.edge_dfs(nx.DiGraph(edges), nodes)) + [(0, 1), (1, 0), (2, 1), (3, 1)] + + >>> list(nx.edge_dfs(nx.MultiGraph(edges), nodes)) + [(0, 1, 0), (1, 0, 1), (0, 1, 2), (1, 2, 0), (1, 3, 0)] + + >>> list(nx.edge_dfs(nx.MultiDiGraph(edges), nodes)) + [(0, 1, 0), (1, 0, 0), (1, 0, 1), (2, 1, 0), (3, 1, 0)] + + >>> list(nx.edge_dfs(nx.DiGraph(edges), nodes, orientation="ignore")) + [(0, 1, 'forward'), (1, 0, 'forward'), (2, 1, 'reverse'), (3, 1, 'reverse')] + + >>> list(nx.edge_dfs(nx.MultiDiGraph(edges), nodes, orientation="ignore")) + [(0, 1, 0, 'forward'), (1, 0, 0, 'forward'), (1, 0, 1, 'reverse'), (2, 1, 0, 'reverse'), (3, 1, 0, 'reverse')] + + Notes + ----- + The goal of this function is to visit edges. It differs from the more + familiar depth-first traversal of nodes, as provided by + :func:`~networkx.algorithms.traversal.depth_first_search.dfs_edges`, in + that it does not stop once every node has been visited. In a directed graph + with edges [(0, 1), (1, 2), (2, 1)], the edge (2, 1) would not be visited + if not for the functionality provided by this function. + + See Also + -------- + :func:`~networkx.algorithms.traversal.depth_first_search.dfs_edges` + + """ + nodes = list(G.nbunch_iter(source)) + if not nodes: + return + + directed = G.is_directed() + kwds = {"data": False} + if G.is_multigraph() is True: + kwds["keys"] = True + + # set up edge lookup + if orientation is None: + + def edges_from(node): + return iter(G.edges(node, **kwds)) + + elif not directed or orientation == "original": + + def edges_from(node): + for e in G.edges(node, **kwds): + yield e + (FORWARD,) + + elif orientation == "reverse": + + def edges_from(node): + for e in G.in_edges(node, **kwds): + yield e + (REVERSE,) + + elif orientation == "ignore": + + def edges_from(node): + for e in G.edges(node, **kwds): + yield e + (FORWARD,) + for e in G.in_edges(node, **kwds): + yield e + (REVERSE,) + + else: + raise nx.NetworkXError("invalid orientation argument.") + + # set up formation of edge_id to easily look up if edge already returned + if directed: + + def edge_id(edge): + # remove direction indicator + return edge[:-1] if orientation is not None else edge + + else: + + def edge_id(edge): + # single id for undirected requires frozenset on nodes + return (frozenset(edge[:2]),) + edge[2:] + + # Basic setup + check_reverse = directed and orientation in ("reverse", "ignore") + + visited_edges = set() + visited_nodes = set() + edges = {} + + # start DFS + for start_node in nodes: + stack = [start_node] + while stack: + current_node = stack[-1] + if current_node not in visited_nodes: + edges[current_node] = edges_from(current_node) + visited_nodes.add(current_node) + + try: + edge = next(edges[current_node]) + except StopIteration: + # No more edges from the current node. + stack.pop() + else: + edgeid = edge_id(edge) + if edgeid not in visited_edges: + visited_edges.add(edgeid) + # Mark the traversed "to" node as to-be-explored. + if check_reverse and edge[-1] == REVERSE: + stack.append(edge[0]) + else: + stack.append(edge[1]) + yield edge diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__init__.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__init__.py new file mode 100644 index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__pycache__/__init__.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__pycache__/__init__.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..d0622a62c64e3e5d2247d9a0dca226530e5a566c Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__pycache__/__init__.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__pycache__/test_edgebfs.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__pycache__/test_edgebfs.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..9755e47d330c40bea9debf7a2a1bb4a0f630e00c Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/__pycache__/test_edgebfs.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_bfs.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_bfs.py new file mode 100644 index 0000000000000000000000000000000000000000..fcfbbc68dc113fe3363233a98faa3e99d44df689 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_bfs.py @@ -0,0 +1,203 @@ +from functools import partial + +import pytest + +import networkx as nx + + +class TestBFS: + @classmethod + def setup_class(cls): + # simple graph + G = nx.Graph() + G.add_edges_from([(0, 1), (1, 2), (1, 3), (2, 4), (3, 4)]) + cls.G = G + + def test_successor(self): + assert dict(nx.bfs_successors(self.G, source=0)) == {0: [1], 1: [2, 3], 2: [4]} + + def test_predecessor(self): + assert dict(nx.bfs_predecessors(self.G, source=0)) == {1: 0, 2: 1, 3: 1, 4: 2} + + def test_bfs_tree(self): + T = nx.bfs_tree(self.G, source=0) + assert sorted(T.nodes()) == sorted(self.G.nodes()) + assert sorted(T.edges()) == [(0, 1), (1, 2), (1, 3), (2, 4)] + + def test_bfs_edges(self): + edges = nx.bfs_edges(self.G, source=0) + assert list(edges) == [(0, 1), (1, 2), (1, 3), (2, 4)] + + def test_bfs_edges_reverse(self): + D = nx.DiGraph() + D.add_edges_from([(0, 1), (1, 2), (1, 3), (2, 4), (3, 4)]) + edges = nx.bfs_edges(D, source=4, reverse=True) + assert list(edges) == [(4, 2), (4, 3), (2, 1), (1, 0)] + + def test_bfs_edges_sorting(self): + D = nx.DiGraph() + D.add_edges_from([(0, 1), (0, 2), (1, 4), (1, 3), (2, 5)]) + sort_desc = partial(sorted, reverse=True) + edges_asc = nx.bfs_edges(D, source=0, sort_neighbors=sorted) + edges_desc = nx.bfs_edges(D, source=0, sort_neighbors=sort_desc) + assert list(edges_asc) == [(0, 1), (0, 2), (1, 3), (1, 4), (2, 5)] + assert list(edges_desc) == [(0, 2), (0, 1), (2, 5), (1, 4), (1, 3)] + + def test_bfs_tree_isolates(self): + G = nx.Graph() + G.add_node(1) + G.add_node(2) + T = nx.bfs_tree(G, source=1) + assert sorted(T.nodes()) == [1] + assert sorted(T.edges()) == [] + + def test_bfs_layers(self): + expected = { + 0: [0], + 1: [1], + 2: [2, 3], + 3: [4], + } + assert dict(enumerate(nx.bfs_layers(self.G, sources=[0]))) == expected + assert dict(enumerate(nx.bfs_layers(self.G, sources=0))) == expected + + def test_bfs_layers_missing_source(self): + with pytest.raises(nx.NetworkXError): + next(nx.bfs_layers(self.G, sources="abc")) + with pytest.raises(nx.NetworkXError): + next(nx.bfs_layers(self.G, sources=["abc"])) + + def test_descendants_at_distance(self): + for distance, descendants in enumerate([{0}, {1}, {2, 3}, {4}]): + assert nx.descendants_at_distance(self.G, 0, distance) == descendants + + def test_descendants_at_distance_missing_source(self): + with pytest.raises(nx.NetworkXError): + nx.descendants_at_distance(self.G, "abc", 0) + + def test_bfs_labeled_edges_directed(self): + D = nx.cycle_graph(5, create_using=nx.DiGraph) + expected = [ + (0, 1, "tree"), + (1, 2, "tree"), + (2, 3, "tree"), + (3, 4, "tree"), + (4, 0, "reverse"), + ] + answer = list(nx.bfs_labeled_edges(D, 0)) + assert expected == answer + + D.add_edge(4, 4) + expected.append((4, 4, "level")) + answer = list(nx.bfs_labeled_edges(D, 0)) + assert expected == answer + + D.add_edge(0, 2) + D.add_edge(1, 5) + D.add_edge(2, 5) + D.remove_edge(4, 4) + expected = [ + (0, 1, "tree"), + (0, 2, "tree"), + (1, 2, "level"), + (1, 5, "tree"), + (2, 3, "tree"), + (2, 5, "forward"), + (3, 4, "tree"), + (4, 0, "reverse"), + ] + answer = list(nx.bfs_labeled_edges(D, 0)) + assert expected == answer + + G = D.to_undirected() + G.add_edge(4, 4) + expected = [ + (0, 1, "tree"), + (0, 2, "tree"), + (0, 4, "tree"), + (1, 2, "level"), + (1, 5, "tree"), + (2, 3, "tree"), + (2, 5, "forward"), + (4, 3, "forward"), + (4, 4, "level"), + ] + answer = list(nx.bfs_labeled_edges(G, 0)) + assert expected == answer + + +class TestBreadthLimitedSearch: + @classmethod + def setup_class(cls): + # a tree + G = nx.Graph() + nx.add_path(G, [0, 1, 2, 3, 4, 5, 6]) + nx.add_path(G, [2, 7, 8, 9, 10]) + cls.G = G + # a disconnected graph + D = nx.Graph() + D.add_edges_from([(0, 1), (2, 3)]) + nx.add_path(D, [2, 7, 8, 9, 10]) + cls.D = D + + def test_limited_bfs_successor(self): + assert dict(nx.bfs_successors(self.G, source=1, depth_limit=3)) == { + 1: [0, 2], + 2: [3, 7], + 3: [4], + 7: [8], + } + result = { + n: sorted(s) for n, s in nx.bfs_successors(self.D, source=7, depth_limit=2) + } + assert result == {8: [9], 2: [3], 7: [2, 8]} + + def test_limited_bfs_predecessor(self): + assert dict(nx.bfs_predecessors(self.G, source=1, depth_limit=3)) == { + 0: 1, + 2: 1, + 3: 2, + 4: 3, + 7: 2, + 8: 7, + } + assert dict(nx.bfs_predecessors(self.D, source=7, depth_limit=2)) == { + 2: 7, + 3: 2, + 8: 7, + 9: 8, + } + + def test_limited_bfs_tree(self): + T = nx.bfs_tree(self.G, source=3, depth_limit=1) + assert sorted(T.edges()) == [(3, 2), (3, 4)] + + def test_limited_bfs_edges(self): + edges = nx.bfs_edges(self.G, source=9, depth_limit=4) + assert list(edges) == [(9, 8), (9, 10), (8, 7), (7, 2), (2, 1), (2, 3)] + + def test_limited_bfs_layers(self): + assert dict(enumerate(nx.bfs_layers(self.G, sources=[0]))) == { + 0: [0], + 1: [1], + 2: [2], + 3: [3, 7], + 4: [4, 8], + 5: [5, 9], + 6: [6, 10], + } + assert dict(enumerate(nx.bfs_layers(self.D, sources=2))) == { + 0: [2], + 1: [3, 7], + 2: [8], + 3: [9], + 4: [10], + } + + def test_limited_descendants_at_distance(self): + for distance, descendants in enumerate( + [{0}, {1}, {2}, {3, 7}, {4, 8}, {5, 9}, {6, 10}] + ): + assert nx.descendants_at_distance(self.G, 0, distance) == descendants + for distance, descendants in enumerate([{2}, {3, 7}, {8}, {9}, {10}]): + assert nx.descendants_at_distance(self.D, 2, distance) == descendants diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_edgebfs.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_edgebfs.py new file mode 100644 index 0000000000000000000000000000000000000000..1bf3fae0bd067dd548281e3382a6125f6e50ee22 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_edgebfs.py @@ -0,0 +1,147 @@ +import pytest + +import networkx as nx +from networkx.algorithms.traversal.edgedfs import FORWARD, REVERSE + + +class TestEdgeBFS: + @classmethod + def setup_class(cls): + cls.nodes = [0, 1, 2, 3] + cls.edges = [(0, 1), (1, 0), (1, 0), (2, 0), (2, 1), (3, 1)] + + def test_empty(self): + G = nx.Graph() + edges = list(nx.edge_bfs(G)) + assert edges == [] + + def test_graph_single_source(self): + G = nx.Graph(self.edges) + G.add_edge(4, 5) + x = list(nx.edge_bfs(G, [0])) + x_ = [(0, 1), (0, 2), (1, 2), (1, 3)] + assert x == x_ + + def test_graph(self): + G = nx.Graph(self.edges) + x = list(nx.edge_bfs(G, self.nodes)) + x_ = [(0, 1), (0, 2), (1, 2), (1, 3)] + assert x == x_ + + def test_digraph(self): + G = nx.DiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes)) + x_ = [(0, 1), (1, 0), (2, 0), (2, 1), (3, 1)] + assert x == x_ + + def test_digraph_orientation_invalid(self): + G = nx.DiGraph(self.edges) + edge_iterator = nx.edge_bfs(G, self.nodes, orientation="hello") + pytest.raises(nx.NetworkXError, list, edge_iterator) + + def test_digraph_orientation_none(self): + G = nx.DiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes, orientation=None)) + x_ = [(0, 1), (1, 0), (2, 0), (2, 1), (3, 1)] + assert x == x_ + + def test_digraph_orientation_original(self): + G = nx.DiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes, orientation="original")) + x_ = [ + (0, 1, FORWARD), + (1, 0, FORWARD), + (2, 0, FORWARD), + (2, 1, FORWARD), + (3, 1, FORWARD), + ] + assert x == x_ + + def test_digraph2(self): + G = nx.DiGraph() + nx.add_path(G, range(4)) + x = list(nx.edge_bfs(G, [0])) + x_ = [(0, 1), (1, 2), (2, 3)] + assert x == x_ + + def test_digraph_rev(self): + G = nx.DiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes, orientation="reverse")) + x_ = [ + (1, 0, REVERSE), + (2, 0, REVERSE), + (0, 1, REVERSE), + (2, 1, REVERSE), + (3, 1, REVERSE), + ] + assert x == x_ + + def test_digraph_rev2(self): + G = nx.DiGraph() + nx.add_path(G, range(4)) + x = list(nx.edge_bfs(G, [3], orientation="reverse")) + x_ = [(2, 3, REVERSE), (1, 2, REVERSE), (0, 1, REVERSE)] + assert x == x_ + + def test_multigraph(self): + G = nx.MultiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes)) + x_ = [(0, 1, 0), (0, 1, 1), (0, 1, 2), (0, 2, 0), (1, 2, 0), (1, 3, 0)] + # This is an example of where hash randomization can break. + # There are 3! * 2 alternative outputs, such as: + # [(0, 1, 1), (1, 0, 0), (0, 1, 2), (1, 3, 0), (1, 2, 0)] + # But note, the edges (1,2,0) and (1,3,0) always follow the (0,1,k) + # edges. So the algorithm only guarantees a partial order. A total + # order is guaranteed only if the graph data structures are ordered. + assert x == x_ + + def test_multidigraph(self): + G = nx.MultiDiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes)) + x_ = [(0, 1, 0), (1, 0, 0), (1, 0, 1), (2, 0, 0), (2, 1, 0), (3, 1, 0)] + assert x == x_ + + def test_multidigraph_rev(self): + G = nx.MultiDiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes, orientation="reverse")) + x_ = [ + (1, 0, 0, REVERSE), + (1, 0, 1, REVERSE), + (2, 0, 0, REVERSE), + (0, 1, 0, REVERSE), + (2, 1, 0, REVERSE), + (3, 1, 0, REVERSE), + ] + assert x == x_ + + def test_digraph_ignore(self): + G = nx.DiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes, orientation="ignore")) + x_ = [ + (0, 1, FORWARD), + (1, 0, REVERSE), + (2, 0, REVERSE), + (2, 1, REVERSE), + (3, 1, REVERSE), + ] + assert x == x_ + + def test_digraph_ignore2(self): + G = nx.DiGraph() + nx.add_path(G, range(4)) + x = list(nx.edge_bfs(G, [0], orientation="ignore")) + x_ = [(0, 1, FORWARD), (1, 2, FORWARD), (2, 3, FORWARD)] + assert x == x_ + + def test_multidigraph_ignore(self): + G = nx.MultiDiGraph(self.edges) + x = list(nx.edge_bfs(G, self.nodes, orientation="ignore")) + x_ = [ + (0, 1, 0, FORWARD), + (1, 0, 0, REVERSE), + (1, 0, 1, REVERSE), + (2, 0, 0, REVERSE), + (2, 1, 0, REVERSE), + (3, 1, 0, REVERSE), + ] + assert x == x_ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_edgedfs.py b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_edgedfs.py new file mode 100644 index 0000000000000000000000000000000000000000..7c1967cce04b3a0c9db80f9af39d7b1dfd8ef4cb --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/traversal/tests/test_edgedfs.py @@ -0,0 +1,131 @@ +import pytest + +import networkx as nx +from networkx.algorithms import edge_dfs +from networkx.algorithms.traversal.edgedfs import FORWARD, REVERSE + +# These tests can fail with hash randomization. The easiest and clearest way +# to write these unit tests is for the edges to be output in an expected total +# order, but we cannot guarantee the order amongst outgoing edges from a node, +# unless each class uses an ordered data structure for neighbors. This is +# painful to do with the current API. The alternative is that the tests are +# written (IMO confusingly) so that there is not a total order over the edges, +# but only a partial order. Due to the small size of the graphs, hopefully +# failures due to hash randomization will not occur. For an example of how +# this can fail, see TestEdgeDFS.test_multigraph. + + +class TestEdgeDFS: + @classmethod + def setup_class(cls): + cls.nodes = [0, 1, 2, 3] + cls.edges = [(0, 1), (1, 0), (1, 0), (2, 1), (3, 1)] + + def test_empty(self): + G = nx.Graph() + edges = list(edge_dfs(G)) + assert edges == [] + + def test_graph(self): + G = nx.Graph(self.edges) + x = list(edge_dfs(G, self.nodes)) + x_ = [(0, 1), (1, 2), (1, 3)] + assert x == x_ + + def test_digraph(self): + G = nx.DiGraph(self.edges) + x = list(edge_dfs(G, self.nodes)) + x_ = [(0, 1), (1, 0), (2, 1), (3, 1)] + assert x == x_ + + def test_digraph_orientation_invalid(self): + G = nx.DiGraph(self.edges) + edge_iterator = edge_dfs(G, self.nodes, orientation="hello") + pytest.raises(nx.NetworkXError, list, edge_iterator) + + def test_digraph_orientation_none(self): + G = nx.DiGraph(self.edges) + x = list(edge_dfs(G, self.nodes, orientation=None)) + x_ = [(0, 1), (1, 0), (2, 1), (3, 1)] + assert x == x_ + + def test_digraph_orientation_original(self): + G = nx.DiGraph(self.edges) + x = list(edge_dfs(G, self.nodes, orientation="original")) + x_ = [(0, 1, FORWARD), (1, 0, FORWARD), (2, 1, FORWARD), (3, 1, FORWARD)] + assert x == x_ + + def test_digraph2(self): + G = nx.DiGraph() + nx.add_path(G, range(4)) + x = list(edge_dfs(G, [0])) + x_ = [(0, 1), (1, 2), (2, 3)] + assert x == x_ + + def test_digraph_rev(self): + G = nx.DiGraph(self.edges) + x = list(edge_dfs(G, self.nodes, orientation="reverse")) + x_ = [(1, 0, REVERSE), (0, 1, REVERSE), (2, 1, REVERSE), (3, 1, REVERSE)] + assert x == x_ + + def test_digraph_rev2(self): + G = nx.DiGraph() + nx.add_path(G, range(4)) + x = list(edge_dfs(G, [3], orientation="reverse")) + x_ = [(2, 3, REVERSE), (1, 2, REVERSE), (0, 1, REVERSE)] + assert x == x_ + + def test_multigraph(self): + G = nx.MultiGraph(self.edges) + x = list(edge_dfs(G, self.nodes)) + x_ = [(0, 1, 0), (1, 0, 1), (0, 1, 2), (1, 2, 0), (1, 3, 0)] + # This is an example of where hash randomization can break. + # There are 3! * 2 alternative outputs, such as: + # [(0, 1, 1), (1, 0, 0), (0, 1, 2), (1, 3, 0), (1, 2, 0)] + # But note, the edges (1,2,0) and (1,3,0) always follow the (0,1,k) + # edges. So the algorithm only guarantees a partial order. A total + # order is guaranteed only if the graph data structures are ordered. + assert x == x_ + + def test_multidigraph(self): + G = nx.MultiDiGraph(self.edges) + x = list(edge_dfs(G, self.nodes)) + x_ = [(0, 1, 0), (1, 0, 0), (1, 0, 1), (2, 1, 0), (3, 1, 0)] + assert x == x_ + + def test_multidigraph_rev(self): + G = nx.MultiDiGraph(self.edges) + x = list(edge_dfs(G, self.nodes, orientation="reverse")) + x_ = [ + (1, 0, 0, REVERSE), + (0, 1, 0, REVERSE), + (1, 0, 1, REVERSE), + (2, 1, 0, REVERSE), + (3, 1, 0, REVERSE), + ] + assert x == x_ + + def test_digraph_ignore(self): + G = nx.DiGraph(self.edges) + x = list(edge_dfs(G, self.nodes, orientation="ignore")) + x_ = [(0, 1, FORWARD), (1, 0, FORWARD), (2, 1, REVERSE), (3, 1, REVERSE)] + assert x == x_ + + def test_digraph_ignore2(self): + G = nx.DiGraph() + nx.add_path(G, range(4)) + x = list(edge_dfs(G, [0], orientation="ignore")) + x_ = [(0, 1, FORWARD), (1, 2, FORWARD), (2, 3, FORWARD)] + assert x == x_ + + def test_multidigraph_ignore(self): + G = nx.MultiDiGraph(self.edges) + x = list(edge_dfs(G, self.nodes, orientation="ignore")) + x_ = [ + (0, 1, 0, FORWARD), + (1, 0, 0, FORWARD), + (1, 0, 1, REVERSE), + (2, 1, 0, REVERSE), + (3, 1, 0, REVERSE), + ] + assert x == x_ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/coding.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/coding.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..bfaa3044242df77296eb82527d70efa8d685e5fc Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/coding.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/mst.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/mst.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..c99d72b5587395e0ea8117a9c80e2f0260d9da9f Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/mst.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/recognition.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/recognition.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..85ec5db758bdd9cfe5c888c8fea2a8023237a1e3 Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/__pycache__/recognition.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/branchings.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/branchings.py new file mode 100644 index 0000000000000000000000000000000000000000..cc9c7cf1189d341577a81501e5ca6760ed73a58c --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/branchings.py @@ -0,0 +1,1042 @@ +""" +Algorithms for finding optimum branchings and spanning arborescences. + +This implementation is based on: + + J. Edmonds, Optimum branchings, J. Res. Natl. Bur. Standards 71B (1967), + 233–240. URL: http://archive.org/details/jresv71Bn4p233 + +""" + +# TODO: Implement method from Gabow, Galil, Spence and Tarjan: +# +# @article{ +# year={1986}, +# issn={0209-9683}, +# journal={Combinatorica}, +# volume={6}, +# number={2}, +# doi={10.1007/BF02579168}, +# title={Efficient algorithms for finding minimum spanning trees in +# undirected and directed graphs}, +# url={https://doi.org/10.1007/BF02579168}, +# publisher={Springer-Verlag}, +# keywords={68 B 15; 68 C 05}, +# author={Gabow, Harold N. and Galil, Zvi and Spencer, Thomas and Tarjan, +# Robert E.}, +# pages={109-122}, +# language={English} +# } +import string +from dataclasses import dataclass, field +from operator import itemgetter +from queue import PriorityQueue + +import networkx as nx +from networkx.utils import py_random_state + +from .recognition import is_arborescence, is_branching + +__all__ = [ + "branching_weight", + "greedy_branching", + "maximum_branching", + "minimum_branching", + "minimal_branching", + "maximum_spanning_arborescence", + "minimum_spanning_arborescence", + "ArborescenceIterator", +] + +KINDS = {"max", "min"} + +STYLES = { + "branching": "branching", + "arborescence": "arborescence", + "spanning arborescence": "arborescence", +} + +INF = float("inf") + + +@py_random_state(1) +def random_string(L=15, seed=None): + return "".join([seed.choice(string.ascii_letters) for n in range(L)]) + + +def _min_weight(weight): + return -weight + + +def _max_weight(weight): + return weight + + +@nx._dispatchable(edge_attrs={"attr": "default"}) +def branching_weight(G, attr="weight", default=1): + """ + Returns the total weight of a branching. + + You must access this function through the networkx.algorithms.tree module. + + Parameters + ---------- + G : DiGraph + The directed graph. + attr : str + The attribute to use as weights. If None, then each edge will be + treated equally with a weight of 1. + default : float + When `attr` is not None, then if an edge does not have that attribute, + `default` specifies what value it should take. + + Returns + ------- + weight: int or float + The total weight of the branching. + + Examples + -------- + >>> G = nx.DiGraph() + >>> G.add_weighted_edges_from([(0, 1, 2), (1, 2, 4), (2, 3, 3), (3, 4, 2)]) + >>> nx.tree.branching_weight(G) + 11 + + """ + return sum(edge[2].get(attr, default) for edge in G.edges(data=True)) + + +@py_random_state(4) +@nx._dispatchable(edge_attrs={"attr": "default"}, returns_graph=True) +def greedy_branching(G, attr="weight", default=1, kind="max", seed=None): + """ + Returns a branching obtained through a greedy algorithm. + + This algorithm is wrong, and cannot give a proper optimal branching. + However, we include it for pedagogical reasons, as it can be helpful to + see what its outputs are. + + The output is a branching, and possibly, a spanning arborescence. However, + it is not guaranteed to be optimal in either case. + + Parameters + ---------- + G : DiGraph + The directed graph to scan. + attr : str + The attribute to use as weights. If None, then each edge will be + treated equally with a weight of 1. + default : float + When `attr` is not None, then if an edge does not have that attribute, + `default` specifies what value it should take. + kind : str + The type of optimum to search for: 'min' or 'max' greedy branching. + seed : integer, random_state, or None (default) + Indicator of random number generation state. + See :ref:`Randomness`. + + Returns + ------- + B : directed graph + The greedily obtained branching. + + """ + if kind not in KINDS: + raise nx.NetworkXException("Unknown value for `kind`.") + + if kind == "min": + reverse = False + else: + reverse = True + + if attr is None: + # Generate a random string the graph probably won't have. + attr = random_string(seed=seed) + + edges = [(u, v, data.get(attr, default)) for (u, v, data) in G.edges(data=True)] + + # We sort by weight, but also by nodes to normalize behavior across runs. + try: + edges.sort(key=itemgetter(2, 0, 1), reverse=reverse) + except TypeError: + # This will fail in Python 3.x if the nodes are of varying types. + # In that case, we use the arbitrary order. + edges.sort(key=itemgetter(2), reverse=reverse) + + # The branching begins with a forest of no edges. + B = nx.DiGraph() + B.add_nodes_from(G) + + # Now we add edges greedily so long we maintain the branching. + uf = nx.utils.UnionFind() + for i, (u, v, w) in enumerate(edges): + if uf[u] == uf[v]: + # Adding this edge would form a directed cycle. + continue + elif B.in_degree(v) == 1: + # The edge would increase the degree to be greater than one. + continue + else: + # If attr was None, then don't insert weights... + data = {} + if attr is not None: + data[attr] = w + B.add_edge(u, v, **data) + uf.union(u, v) + + return B + + +@nx._dispatchable(preserve_edge_attrs=True, returns_graph=True) +def maximum_branching( + G, + attr="weight", + default=1, + preserve_attrs=False, + partition=None, +): + ####################################### + ### Data Structure Helper Functions ### + ####################################### + + def edmonds_add_edge(G, edge_index, u, v, key, **d): + """ + Adds an edge to `G` while also updating the edge index. + + This algorithm requires the use of an external dictionary to track + the edge keys since it is possible that the source or destination + node of an edge will be changed and the default key-handling + capabilities of the MultiDiGraph class do not account for this. + + Parameters + ---------- + G : MultiDiGraph + The graph to insert an edge into. + edge_index : dict + A mapping from integers to the edges of the graph. + u : node + The source node of the new edge. + v : node + The destination node of the new edge. + key : int + The key to use from `edge_index`. + d : keyword arguments, optional + Other attributes to store on the new edge. + """ + + if key in edge_index: + uu, vv, _ = edge_index[key] + if (u != uu) or (v != vv): + raise Exception(f"Key {key!r} is already in use.") + + G.add_edge(u, v, key, **d) + edge_index[key] = (u, v, G.succ[u][v][key]) + + def edmonds_remove_node(G, edge_index, n): + """ + Remove a node from the graph, updating the edge index to match. + + Parameters + ---------- + G : MultiDiGraph + The graph to remove an edge from. + edge_index : dict + A mapping from integers to the edges of the graph. + n : node + The node to remove from `G`. + """ + keys = set() + for keydict in G.pred[n].values(): + keys.update(keydict) + for keydict in G.succ[n].values(): + keys.update(keydict) + + for key in keys: + del edge_index[key] + + G.remove_node(n) + + ####################### + ### Algorithm Setup ### + ####################### + + # Pick an attribute name that the original graph is unlikly to have + candidate_attr = "edmonds' secret candidate attribute" + new_node_base_name = "edmonds new node base name " + + G_original = G + G = nx.MultiDiGraph() + G.__networkx_cache__ = None # Disable caching + + # A dict to reliably track mutations to the edges using the key of the edge. + G_edge_index = {} + # Each edge is given an arbitrary numerical key + for key, (u, v, data) in enumerate(G_original.edges(data=True)): + d = {attr: data.get(attr, default)} + + if data.get(partition) is not None: + d[partition] = data.get(partition) + + if preserve_attrs: + for d_k, d_v in data.items(): + if d_k != attr: + d[d_k] = d_v + + edmonds_add_edge(G, G_edge_index, u, v, key, **d) + + level = 0 # Stores the number of contracted nodes + + # These are the buckets from the paper. + # + # In the paper, G^i are modified versions of the original graph. + # D^i and E^i are the nodes and edges of the maximal edges that are + # consistent with G^i. In this implementation, D^i and E^i are stored + # together as the graph B^i. We will have strictly more B^i then the + # paper will have. + # + # Note that the data in graphs and branchings are tuples with the graph as + # the first element and the edge index as the second. + B = nx.MultiDiGraph() + B_edge_index = {} + graphs = [] # G^i list + branchings = [] # B^i list + selected_nodes = set() # D^i bucket + uf = nx.utils.UnionFind() + + # A list of lists of edge indices. Each list is a circuit for graph G^i. + # Note the edge list is not required to be a circuit in G^0. + circuits = [] + + # Stores the index of the minimum edge in the circuit found in G^i and B^i. + # The ordering of the edges seems to preserver the weight ordering from + # G^0. So even if the circuit does not form a circuit in G^0, it is still + # true that the minimum edges in circuit G^0 (despite their weights being + # different) + minedge_circuit = [] + + ########################### + ### Algorithm Structure ### + ########################### + + # Each step listed in the algorithm is an inner function. Thus, the overall + # loop structure is: + # + # while True: + # step_I1() + # if cycle detected: + # step_I2() + # elif every node of G is in D and E is a branching: + # break + + ################################## + ### Algorithm Helper Functions ### + ################################## + + def edmonds_find_desired_edge(v): + """ + Find the edge directed towards v with maximal weight. + + If an edge partition exists in this graph, return the included + edge if it exists and never return any excluded edge. + + Note: There can only be one included edge for each vertex otherwise + the edge partition is empty. + + Parameters + ---------- + v : node + The node to search for the maximal weight incoming edge. + """ + edge = None + max_weight = -INF + for u, _, key, data in G.in_edges(v, data=True, keys=True): + # Skip excluded edges + if data.get(partition) == nx.EdgePartition.EXCLUDED: + continue + + new_weight = data[attr] + + # Return the included edge + if data.get(partition) == nx.EdgePartition.INCLUDED: + max_weight = new_weight + edge = (u, v, key, new_weight, data) + break + + # Find the best open edge + if new_weight > max_weight: + max_weight = new_weight + edge = (u, v, key, new_weight, data) + + return edge, max_weight + + def edmonds_step_I2(v, desired_edge, level): + """ + Perform step I2 from Edmonds' paper + + First, check if the last step I1 created a cycle. If it did not, do nothing. + If it did, store the cycle for later reference and contract it. + + Parameters + ---------- + v : node + The current node to consider + desired_edge : edge + The minimum desired edge to remove from the cycle. + level : int + The current level, i.e. the number of cycles that have already been removed. + """ + u = desired_edge[0] + + Q_nodes = nx.shortest_path(B, v, u) + Q_edges = [ + list(B[Q_nodes[i]][vv].keys())[0] for i, vv in enumerate(Q_nodes[1:]) + ] + Q_edges.append(desired_edge[2]) # Add the new edge key to complete the circuit + + # Get the edge in the circuit with the minimum weight. + # Also, save the incoming weights for each node. + minweight = INF + minedge = None + Q_incoming_weight = {} + for edge_key in Q_edges: + u, v, data = B_edge_index[edge_key] + w = data[attr] + # We cannot remove an included edge, even if it is the + # minimum edge in the circuit + Q_incoming_weight[v] = w + if data.get(partition) == nx.EdgePartition.INCLUDED: + continue + if w < minweight: + minweight = w + minedge = edge_key + + circuits.append(Q_edges) + minedge_circuit.append(minedge) + graphs.append((G.copy(), G_edge_index.copy())) + branchings.append((B.copy(), B_edge_index.copy())) + + # Mutate the graph to contract the circuit + new_node = new_node_base_name + str(level) + G.add_node(new_node) + new_edges = [] + for u, v, key, data in G.edges(data=True, keys=True): + if u in Q_incoming_weight: + if v in Q_incoming_weight: + # Circuit edge. For the moment do nothing, + # eventually it will be removed. + continue + else: + # Outgoing edge from a node in the circuit. + # Make it come from the new node instead + dd = data.copy() + new_edges.append((new_node, v, key, dd)) + else: + if v in Q_incoming_weight: + # Incoming edge to the circuit. + # Update it's weight + w = data[attr] + w += minweight - Q_incoming_weight[v] + dd = data.copy() + dd[attr] = w + new_edges.append((u, new_node, key, dd)) + else: + # Outside edge. No modification needed + continue + + for node in Q_nodes: + edmonds_remove_node(G, G_edge_index, node) + edmonds_remove_node(B, B_edge_index, node) + + selected_nodes.difference_update(set(Q_nodes)) + + for u, v, key, data in new_edges: + edmonds_add_edge(G, G_edge_index, u, v, key, **data) + if candidate_attr in data: + del data[candidate_attr] + edmonds_add_edge(B, B_edge_index, u, v, key, **data) + uf.union(u, v) + + def is_root(G, u, edgekeys): + """ + Returns True if `u` is a root node in G. + + Node `u` is a root node if its in-degree over the specified edges is zero. + + Parameters + ---------- + G : Graph + The current graph. + u : node + The node in `G` to check if it is a root. + edgekeys : iterable of edges + The edges for which to check if `u` is a root of. + """ + if u not in G: + raise Exception(f"{u!r} not in G") + + for v in G.pred[u]: + for edgekey in G.pred[u][v]: + if edgekey in edgekeys: + return False, edgekey + else: + return True, None + + nodes = iter(list(G.nodes)) + while True: + try: + v = next(nodes) + except StopIteration: + # If there are no more new nodes to consider, then we should + # meet stopping condition (b) from the paper: + # (b) every node of G^i is in D^i and E^i is a branching + assert len(G) == len(B) + if len(B): + assert is_branching(B) + + graphs.append((G.copy(), G_edge_index.copy())) + branchings.append((B.copy(), B_edge_index.copy())) + circuits.append([]) + minedge_circuit.append(None) + + break + else: + ##################### + ### BEGIN STEP I1 ### + ##################### + + # This is a very simple step, so I don't think it needs a method of it's own + if v in selected_nodes: + continue + + selected_nodes.add(v) + B.add_node(v) + desired_edge, desired_edge_weight = edmonds_find_desired_edge(v) + + # There might be no desired edge if all edges are excluded or + # v is the last node to be added to B, the ultimate root of the branching + if desired_edge is not None and desired_edge_weight > 0: + u = desired_edge[0] + # Flag adding the edge will create a circuit before merging the two + # connected components of u and v in B + circuit = uf[u] == uf[v] + dd = {attr: desired_edge_weight} + if desired_edge[4].get(partition) is not None: + dd[partition] = desired_edge[4].get(partition) + + edmonds_add_edge(B, B_edge_index, u, v, desired_edge[2], **dd) + G[u][v][desired_edge[2]][candidate_attr] = True + uf.union(u, v) + + ################### + ### END STEP I1 ### + ################### + + ##################### + ### BEGIN STEP I2 ### + ##################### + + if circuit: + edmonds_step_I2(v, desired_edge, level) + nodes = iter(list(G.nodes())) + level += 1 + + ################### + ### END STEP I2 ### + ################### + + ##################### + ### BEGIN STEP I3 ### + ##################### + + # Create a new graph of the same class as the input graph + H = G_original.__class__() + + # Start with the branching edges in the last level. + edges = set(branchings[level][1]) + while level > 0: + level -= 1 + + # The current level is i, and we start counting from 0. + # + # We need the node at level i+1 that results from merging a circuit + # at level i. basename_0 is the first merged node and this happens + # at level 1. That is basename_0 is a node at level 1 that results + # from merging a circuit at level 0. + + merged_node = new_node_base_name + str(level) + circuit = circuits[level] + isroot, edgekey = is_root(graphs[level + 1][0], merged_node, edges) + edges.update(circuit) + + if isroot: + minedge = minedge_circuit[level] + if minedge is None: + raise Exception + + # Remove the edge in the cycle with minimum weight + edges.remove(minedge) + else: + # We have identified an edge at the next higher level that + # transitions into the merged node at this level. That edge + # transitions to some corresponding node at the current level. + # + # We want to remove an edge from the cycle that transitions + # into the corresponding node, otherwise the result would not + # be a branching. + + G, G_edge_index = graphs[level] + target = G_edge_index[edgekey][1] + for edgekey in circuit: + u, v, data = G_edge_index[edgekey] + if v == target: + break + else: + raise Exception("Couldn't find edge incoming to merged node.") + + edges.remove(edgekey) + + H.add_nodes_from(G_original) + for edgekey in edges: + u, v, d = graphs[0][1][edgekey] + dd = {attr: d[attr]} + + if preserve_attrs: + for key, value in d.items(): + if key not in [attr, candidate_attr]: + dd[key] = value + + H.add_edge(u, v, **dd) + + ################### + ### END STEP I3 ### + ################### + + return H + + +@nx._dispatchable(preserve_edge_attrs=True, mutates_input=True, returns_graph=True) +def minimum_branching( + G, attr="weight", default=1, preserve_attrs=False, partition=None +): + for _, _, d in G.edges(data=True): + d[attr] = -d.get(attr, default) + nx._clear_cache(G) + + B = maximum_branching(G, attr, default, preserve_attrs, partition) + + for _, _, d in G.edges(data=True): + d[attr] = -d.get(attr, default) + nx._clear_cache(G) + + for _, _, d in B.edges(data=True): + d[attr] = -d.get(attr, default) + nx._clear_cache(B) + + return B + + +@nx._dispatchable(preserve_edge_attrs=True, mutates_input=True, returns_graph=True) +def minimal_branching( + G, /, *, attr="weight", default=1, preserve_attrs=False, partition=None +): + """ + Returns a minimal branching from `G`. + + A minimal branching is a branching similar to a minimal arborescence but + without the requirement that the result is actually a spanning arborescence. + This allows minimal branchinges to be computed over graphs which may not + have arborescence (such as multiple components). + + Parameters + ---------- + G : (multi)digraph-like + The graph to be searched. + attr : str + The edge attribute used in determining optimality. + default : float + The value of the edge attribute used if an edge does not have + the attribute `attr`. + preserve_attrs : bool + If True, preserve the other attributes of the original graph (that are not + passed to `attr`) + partition : str + The key for the edge attribute containing the partition + data on the graph. Edges can be included, excluded or open using the + `EdgePartition` enum. + + Returns + ------- + B : (multi)digraph-like + A minimal branching. + """ + max_weight = -INF + min_weight = INF + for _, _, w in G.edges(data=attr, default=default): + if w > max_weight: + max_weight = w + if w < min_weight: + min_weight = w + + for _, _, d in G.edges(data=True): + # Transform the weights so that the minimum weight is larger than + # the difference between the max and min weights. This is important + # in order to prevent the edge weights from becoming negative during + # computation + d[attr] = max_weight + 1 + (max_weight - min_weight) - d.get(attr, default) + nx._clear_cache(G) + + B = maximum_branching(G, attr, default, preserve_attrs, partition) + + # Reverse the weight transformations + for _, _, d in G.edges(data=True): + d[attr] = max_weight + 1 + (max_weight - min_weight) - d.get(attr, default) + nx._clear_cache(G) + + for _, _, d in B.edges(data=True): + d[attr] = max_weight + 1 + (max_weight - min_weight) - d.get(attr, default) + nx._clear_cache(B) + + return B + + +@nx._dispatchable(preserve_edge_attrs=True, mutates_input=True, returns_graph=True) +def maximum_spanning_arborescence( + G, attr="weight", default=1, preserve_attrs=False, partition=None +): + # In order to use the same algorithm is the maximum branching, we need to adjust + # the weights of the graph. The branching algorithm can choose to not include an + # edge if it doesn't help find a branching, mainly triggered by edges with negative + # weights. + # + # To prevent this from happening while trying to find a spanning arborescence, we + # just have to tweak the edge weights so that they are all positive and cannot + # become negative during the branching algorithm, find the maximum branching and + # then return them to their original values. + + min_weight = INF + max_weight = -INF + for _, _, w in G.edges(data=attr, default=default): + if w < min_weight: + min_weight = w + if w > max_weight: + max_weight = w + + for _, _, d in G.edges(data=True): + d[attr] = d.get(attr, default) - min_weight + 1 - (min_weight - max_weight) + nx._clear_cache(G) + + B = maximum_branching(G, attr, default, preserve_attrs, partition) + + for _, _, d in G.edges(data=True): + d[attr] = d.get(attr, default) + min_weight - 1 + (min_weight - max_weight) + nx._clear_cache(G) + + for _, _, d in B.edges(data=True): + d[attr] = d.get(attr, default) + min_weight - 1 + (min_weight - max_weight) + nx._clear_cache(B) + + if not is_arborescence(B): + raise nx.exception.NetworkXException("No maximum spanning arborescence in G.") + + return B + + +@nx._dispatchable(preserve_edge_attrs=True, mutates_input=True, returns_graph=True) +def minimum_spanning_arborescence( + G, attr="weight", default=1, preserve_attrs=False, partition=None +): + B = minimal_branching( + G, + attr=attr, + default=default, + preserve_attrs=preserve_attrs, + partition=partition, + ) + + if not is_arborescence(B): + raise nx.exception.NetworkXException("No minimum spanning arborescence in G.") + + return B + + +docstring_branching = """ +Returns a {kind} {style} from G. + +Parameters +---------- +G : (multi)digraph-like + The graph to be searched. +attr : str + The edge attribute used to in determining optimality. +default : float + The value of the edge attribute used if an edge does not have + the attribute `attr`. +preserve_attrs : bool + If True, preserve the other attributes of the original graph (that are not + passed to `attr`) +partition : str + The key for the edge attribute containing the partition + data on the graph. Edges can be included, excluded or open using the + `EdgePartition` enum. + +Returns +------- +B : (multi)digraph-like + A {kind} {style}. +""" + +docstring_arborescence = ( + docstring_branching + + """ +Raises +------ +NetworkXException + If the graph does not contain a {kind} {style}. + +""" +) + +maximum_branching.__doc__ = docstring_branching.format( + kind="maximum", style="branching" +) + +minimum_branching.__doc__ = ( + docstring_branching.format(kind="minimum", style="branching") + + """ +See Also +-------- + minimal_branching +""" +) + +maximum_spanning_arborescence.__doc__ = docstring_arborescence.format( + kind="maximum", style="spanning arborescence" +) + +minimum_spanning_arborescence.__doc__ = docstring_arborescence.format( + kind="minimum", style="spanning arborescence" +) + + +class ArborescenceIterator: + """ + Iterate over all spanning arborescences of a graph in either increasing or + decreasing cost. + + Notes + ----- + This iterator uses the partition scheme from [1]_ (included edges, + excluded edges and open edges). It generates minimum spanning + arborescences using a modified Edmonds' Algorithm which respects the + partition of edges. For arborescences with the same weight, ties are + broken arbitrarily. + + References + ---------- + .. [1] G.K. Janssens, K. Sörensen, An algorithm to generate all spanning + trees in order of increasing cost, Pesquisa Operacional, 2005-08, + Vol. 25 (2), p. 219-229, + https://www.scielo.br/j/pope/a/XHswBwRwJyrfL88dmMwYNWp/?lang=en + """ + + @dataclass(order=True) + class Partition: + """ + This dataclass represents a partition and stores a dict with the edge + data and the weight of the minimum spanning arborescence of the + partition dict. + """ + + mst_weight: float + partition_dict: dict = field(compare=False) + + def __copy__(self): + return ArborescenceIterator.Partition( + self.mst_weight, self.partition_dict.copy() + ) + + def __init__(self, G, weight="weight", minimum=True, init_partition=None): + """ + Initialize the iterator + + Parameters + ---------- + G : nx.DiGraph + The directed graph which we need to iterate trees over + + weight : String, default = "weight" + The edge attribute used to store the weight of the edge + + minimum : bool, default = True + Return the trees in increasing order while true and decreasing order + while false. + + init_partition : tuple, default = None + In the case that certain edges have to be included or excluded from + the arborescences, `init_partition` should be in the form + `(included_edges, excluded_edges)` where each edges is a + `(u, v)`-tuple inside an iterable such as a list or set. + + """ + self.G = G.copy() + self.weight = weight + self.minimum = minimum + self.method = ( + minimum_spanning_arborescence if minimum else maximum_spanning_arborescence + ) + # Randomly create a key for an edge attribute to hold the partition data + self.partition_key = ( + "ArborescenceIterators super secret partition attribute name" + ) + if init_partition is not None: + partition_dict = {} + for e in init_partition[0]: + partition_dict[e] = nx.EdgePartition.INCLUDED + for e in init_partition[1]: + partition_dict[e] = nx.EdgePartition.EXCLUDED + self.init_partition = ArborescenceIterator.Partition(0, partition_dict) + else: + self.init_partition = None + + def __iter__(self): + """ + Returns + ------- + ArborescenceIterator + The iterator object for this graph + """ + self.partition_queue = PriorityQueue() + self._clear_partition(self.G) + + # Write the initial partition if it exists. + if self.init_partition is not None: + self._write_partition(self.init_partition) + + mst_weight = self.method( + self.G, + self.weight, + partition=self.partition_key, + preserve_attrs=True, + ).size(weight=self.weight) + + self.partition_queue.put( + self.Partition( + mst_weight if self.minimum else -mst_weight, + ( + {} + if self.init_partition is None + else self.init_partition.partition_dict + ), + ) + ) + + return self + + def __next__(self): + """ + Returns + ------- + (multi)Graph + The spanning tree of next greatest weight, which ties broken + arbitrarily. + """ + if self.partition_queue.empty(): + del self.G, self.partition_queue + raise StopIteration + + partition = self.partition_queue.get() + self._write_partition(partition) + next_arborescence = self.method( + self.G, + self.weight, + partition=self.partition_key, + preserve_attrs=True, + ) + self._partition(partition, next_arborescence) + + self._clear_partition(next_arborescence) + return next_arborescence + + def _partition(self, partition, partition_arborescence): + """ + Create new partitions based of the minimum spanning tree of the + current minimum partition. + + Parameters + ---------- + partition : Partition + The Partition instance used to generate the current minimum spanning + tree. + partition_arborescence : nx.Graph + The minimum spanning arborescence of the input partition. + """ + # create two new partitions with the data from the input partition dict + p1 = self.Partition(0, partition.partition_dict.copy()) + p2 = self.Partition(0, partition.partition_dict.copy()) + for e in partition_arborescence.edges: + # determine if the edge was open or included + if e not in partition.partition_dict: + # This is an open edge + p1.partition_dict[e] = nx.EdgePartition.EXCLUDED + p2.partition_dict[e] = nx.EdgePartition.INCLUDED + + self._write_partition(p1) + try: + p1_mst = self.method( + self.G, + self.weight, + partition=self.partition_key, + preserve_attrs=True, + ) + + p1_mst_weight = p1_mst.size(weight=self.weight) + p1.mst_weight = p1_mst_weight if self.minimum else -p1_mst_weight + self.partition_queue.put(p1.__copy__()) + except nx.NetworkXException: + pass + + p1.partition_dict = p2.partition_dict.copy() + + def _write_partition(self, partition): + """ + Writes the desired partition into the graph to calculate the minimum + spanning tree. Also, if one incoming edge is included, mark all others + as excluded so that if that vertex is merged during Edmonds' algorithm + we cannot still pick another of that vertex's included edges. + + Parameters + ---------- + partition : Partition + A Partition dataclass describing a partition on the edges of the + graph. + """ + for u, v, d in self.G.edges(data=True): + if (u, v) in partition.partition_dict: + d[self.partition_key] = partition.partition_dict[(u, v)] + else: + d[self.partition_key] = nx.EdgePartition.OPEN + nx._clear_cache(self.G) + + for n in self.G: + included_count = 0 + excluded_count = 0 + for u, v, d in self.G.in_edges(nbunch=n, data=True): + if d.get(self.partition_key) == nx.EdgePartition.INCLUDED: + included_count += 1 + elif d.get(self.partition_key) == nx.EdgePartition.EXCLUDED: + excluded_count += 1 + # Check that if there is an included edges, all other incoming ones + # are excluded. If not fix it! + if included_count == 1 and excluded_count != self.G.in_degree(n) - 1: + for u, v, d in self.G.in_edges(nbunch=n, data=True): + if d.get(self.partition_key) != nx.EdgePartition.INCLUDED: + d[self.partition_key] = nx.EdgePartition.EXCLUDED + + def _clear_partition(self, G): + """ + Removes partition data from the graph + """ + for u, v, d in G.edges(data=True): + if self.partition_key in d: + del d[self.partition_key] + nx._clear_cache(self.G) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/mst.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/mst.py new file mode 100644 index 0000000000000000000000000000000000000000..554613b8f36dae63eb1ce7f4a03a646fd2dc81c4 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/mst.py @@ -0,0 +1,1284 @@ +""" +Algorithms for calculating min/max spanning trees/forests. + +""" + +from dataclasses import dataclass, field +from enum import Enum +from heapq import heappop, heappush +from itertools import count +from math import isnan +from operator import itemgetter +from queue import PriorityQueue + +import networkx as nx +from networkx.utils import UnionFind, not_implemented_for, py_random_state + +__all__ = [ + "minimum_spanning_edges", + "maximum_spanning_edges", + "minimum_spanning_tree", + "maximum_spanning_tree", + "number_of_spanning_trees", + "random_spanning_tree", + "partition_spanning_tree", + "EdgePartition", + "SpanningTreeIterator", +] + + +class EdgePartition(Enum): + """ + An enum to store the state of an edge partition. The enum is written to the + edges of a graph before being pasted to `kruskal_mst_edges`. Options are: + + - EdgePartition.OPEN + - EdgePartition.INCLUDED + - EdgePartition.EXCLUDED + """ + + OPEN = 0 + INCLUDED = 1 + EXCLUDED = 2 + + +@not_implemented_for("multigraph") +@nx._dispatchable(edge_attrs="weight", preserve_edge_attrs="data") +def boruvka_mst_edges( + G, minimum=True, weight="weight", keys=False, data=True, ignore_nan=False +): + """Iterate over edges of a Borůvka's algorithm min/max spanning tree. + + Parameters + ---------- + G : NetworkX Graph + The edges of `G` must have distinct weights, + otherwise the edges may not form a tree. + + minimum : bool (default: True) + Find the minimum (True) or maximum (False) spanning tree. + + weight : string (default: 'weight') + The name of the edge attribute holding the edge weights. + + keys : bool (default: True) + This argument is ignored since this function is not + implemented for multigraphs; it exists only for consistency + with the other minimum spanning tree functions. + + data : bool (default: True) + Flag for whether to yield edge attribute dicts. + If True, yield edges `(u, v, d)`, where `d` is the attribute dict. + If False, yield edges `(u, v)`. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + """ + # Initialize a forest, assuming initially that it is the discrete + # partition of the nodes of the graph. + forest = UnionFind(G) + + def best_edge(component): + """Returns the optimum (minimum or maximum) edge on the edge + boundary of the given set of nodes. + + A return value of ``None`` indicates an empty boundary. + + """ + sign = 1 if minimum else -1 + minwt = float("inf") + boundary = None + for e in nx.edge_boundary(G, component, data=True): + wt = e[-1].get(weight, 1) * sign + if isnan(wt): + if ignore_nan: + continue + msg = f"NaN found as an edge weight. Edge {e}" + raise ValueError(msg) + if wt < minwt: + minwt = wt + boundary = e + return boundary + + # Determine the optimum edge in the edge boundary of each component + # in the forest. + best_edges = (best_edge(component) for component in forest.to_sets()) + best_edges = [edge for edge in best_edges if edge is not None] + # If each entry was ``None``, that means the graph was disconnected, + # so we are done generating the forest. + while best_edges: + # Determine the optimum edge in the edge boundary of each + # component in the forest. + # + # This must be a sequence, not an iterator. In this list, the + # same edge may appear twice, in different orientations (but + # that's okay, since a union operation will be called on the + # endpoints the first time it is seen, but not the second time). + # + # Any ``None`` indicates that the edge boundary for that + # component was empty, so that part of the forest has been + # completed. + # + # TODO This can be parallelized, both in the outer loop over + # each component in the forest and in the computation of the + # minimum. (Same goes for the identical lines outside the loop.) + best_edges = (best_edge(component) for component in forest.to_sets()) + best_edges = [edge for edge in best_edges if edge is not None] + # Join trees in the forest using the best edges, and yield that + # edge, since it is part of the spanning tree. + # + # TODO This loop can be parallelized, to an extent (the union + # operation must be atomic). + for u, v, d in best_edges: + if forest[u] != forest[v]: + if data: + yield u, v, d + else: + yield u, v + forest.union(u, v) + + +@nx._dispatchable( + edge_attrs={"weight": None, "partition": None}, preserve_edge_attrs="data" +) +def kruskal_mst_edges( + G, minimum, weight="weight", keys=True, data=True, ignore_nan=False, partition=None +): + """ + Iterate over edge of a Kruskal's algorithm min/max spanning tree. + + Parameters + ---------- + G : NetworkX Graph + The graph holding the tree of interest. + + minimum : bool (default: True) + Find the minimum (True) or maximum (False) spanning tree. + + weight : string (default: 'weight') + The name of the edge attribute holding the edge weights. + + keys : bool (default: True) + If `G` is a multigraph, `keys` controls whether edge keys ar yielded. + Otherwise `keys` is ignored. + + data : bool (default: True) + Flag for whether to yield edge attribute dicts. + If True, yield edges `(u, v, d)`, where `d` is the attribute dict. + If False, yield edges `(u, v)`. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + partition : string (default: None) + The name of the edge attribute holding the partition data, if it exists. + Partition data is written to the edges using the `EdgePartition` enum. + If a partition exists, all included edges and none of the excluded edges + will appear in the final tree. Open edges may or may not be used. + + Yields + ------ + edge tuple + The edges as discovered by Kruskal's method. Each edge can + take the following forms: `(u, v)`, `(u, v, d)` or `(u, v, k, d)` + depending on the `key` and `data` parameters + """ + subtrees = UnionFind() + if G.is_multigraph(): + edges = G.edges(keys=True, data=True) + else: + edges = G.edges(data=True) + + """ + Sort the edges of the graph with respect to the partition data. + Edges are returned in the following order: + + * Included edges + * Open edges from smallest to largest weight + * Excluded edges + """ + included_edges = [] + open_edges = [] + for e in edges: + d = e[-1] + wt = d.get(weight, 1) + if isnan(wt): + if ignore_nan: + continue + raise ValueError(f"NaN found as an edge weight. Edge {e}") + + edge = (wt,) + e + if d.get(partition) == EdgePartition.INCLUDED: + included_edges.append(edge) + elif d.get(partition) == EdgePartition.EXCLUDED: + continue + else: + open_edges.append(edge) + + if minimum: + sorted_open_edges = sorted(open_edges, key=itemgetter(0)) + else: + sorted_open_edges = sorted(open_edges, key=itemgetter(0), reverse=True) + + # Condense the lists into one + included_edges.extend(sorted_open_edges) + sorted_edges = included_edges + del open_edges, sorted_open_edges, included_edges + + # Multigraphs need to handle edge keys in addition to edge data. + if G.is_multigraph(): + for wt, u, v, k, d in sorted_edges: + if subtrees[u] != subtrees[v]: + if keys: + if data: + yield u, v, k, d + else: + yield u, v, k + else: + if data: + yield u, v, d + else: + yield u, v + subtrees.union(u, v) + else: + for wt, u, v, d in sorted_edges: + if subtrees[u] != subtrees[v]: + if data: + yield u, v, d + else: + yield u, v + subtrees.union(u, v) + + +@nx._dispatchable(edge_attrs="weight", preserve_edge_attrs="data") +def prim_mst_edges(G, minimum, weight="weight", keys=True, data=True, ignore_nan=False): + """Iterate over edges of Prim's algorithm min/max spanning tree. + + Parameters + ---------- + G : NetworkX Graph + The graph holding the tree of interest. + + minimum : bool (default: True) + Find the minimum (True) or maximum (False) spanning tree. + + weight : string (default: 'weight') + The name of the edge attribute holding the edge weights. + + keys : bool (default: True) + If `G` is a multigraph, `keys` controls whether edge keys ar yielded. + Otherwise `keys` is ignored. + + data : bool (default: True) + Flag for whether to yield edge attribute dicts. + If True, yield edges `(u, v, d)`, where `d` is the attribute dict. + If False, yield edges `(u, v)`. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + """ + is_multigraph = G.is_multigraph() + push = heappush + pop = heappop + + nodes = set(G) + c = count() + + sign = 1 if minimum else -1 + + while nodes: + u = nodes.pop() + frontier = [] + visited = {u} + if is_multigraph: + for v, keydict in G.adj[u].items(): + for k, d in keydict.items(): + wt = d.get(weight, 1) * sign + if isnan(wt): + if ignore_nan: + continue + msg = f"NaN found as an edge weight. Edge {(u, v, k, d)}" + raise ValueError(msg) + push(frontier, (wt, next(c), u, v, k, d)) + else: + for v, d in G.adj[u].items(): + wt = d.get(weight, 1) * sign + if isnan(wt): + if ignore_nan: + continue + msg = f"NaN found as an edge weight. Edge {(u, v, d)}" + raise ValueError(msg) + push(frontier, (wt, next(c), u, v, d)) + while nodes and frontier: + if is_multigraph: + W, _, u, v, k, d = pop(frontier) + else: + W, _, u, v, d = pop(frontier) + if v in visited or v not in nodes: + continue + # Multigraphs need to handle edge keys in addition to edge data. + if is_multigraph and keys: + if data: + yield u, v, k, d + else: + yield u, v, k + else: + if data: + yield u, v, d + else: + yield u, v + # update frontier + visited.add(v) + nodes.discard(v) + if is_multigraph: + for w, keydict in G.adj[v].items(): + if w in visited: + continue + for k2, d2 in keydict.items(): + new_weight = d2.get(weight, 1) * sign + if isnan(new_weight): + if ignore_nan: + continue + msg = f"NaN found as an edge weight. Edge {(v, w, k2, d2)}" + raise ValueError(msg) + push(frontier, (new_weight, next(c), v, w, k2, d2)) + else: + for w, d2 in G.adj[v].items(): + if w in visited: + continue + new_weight = d2.get(weight, 1) * sign + if isnan(new_weight): + if ignore_nan: + continue + msg = f"NaN found as an edge weight. Edge {(v, w, d2)}" + raise ValueError(msg) + push(frontier, (new_weight, next(c), v, w, d2)) + + +ALGORITHMS = { + "boruvka": boruvka_mst_edges, + "borůvka": boruvka_mst_edges, + "kruskal": kruskal_mst_edges, + "prim": prim_mst_edges, +} + + +@not_implemented_for("directed") +@nx._dispatchable(edge_attrs="weight", preserve_edge_attrs="data") +def minimum_spanning_edges( + G, algorithm="kruskal", weight="weight", keys=True, data=True, ignore_nan=False +): + """Generate edges in a minimum spanning forest of an undirected + weighted graph. + + A minimum spanning tree is a subgraph of the graph (a tree) + with the minimum sum of edge weights. A spanning forest is a + union of the spanning trees for each connected component of the graph. + + Parameters + ---------- + G : undirected Graph + An undirected graph. If `G` is connected, then the algorithm finds a + spanning tree. Otherwise, a spanning forest is found. + + algorithm : string + The algorithm to use when finding a minimum spanning tree. Valid + choices are 'kruskal', 'prim', or 'boruvka'. The default is 'kruskal'. + + weight : string + Edge data key to use for weight (default 'weight'). + + keys : bool + Whether to yield edge key in multigraphs in addition to the edge. + If `G` is not a multigraph, this is ignored. + + data : bool, optional + If True yield the edge data along with the edge. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + Returns + ------- + edges : iterator + An iterator over edges in a maximum spanning tree of `G`. + Edges connecting nodes `u` and `v` are represented as tuples: + `(u, v, k, d)` or `(u, v, k)` or `(u, v, d)` or `(u, v)` + + If `G` is a multigraph, `keys` indicates whether the edge key `k` will + be reported in the third position in the edge tuple. `data` indicates + whether the edge datadict `d` will appear at the end of the edge tuple. + + If `G` is not a multigraph, the tuples are `(u, v, d)` if `data` is True + or `(u, v)` if `data` is False. + + Examples + -------- + >>> from networkx.algorithms import tree + + Find minimum spanning edges by Kruskal's algorithm + + >>> G = nx.cycle_graph(4) + >>> G.add_edge(0, 3, weight=2) + >>> mst = tree.minimum_spanning_edges(G, algorithm="kruskal", data=False) + >>> edgelist = list(mst) + >>> sorted(sorted(e) for e in edgelist) + [[0, 1], [1, 2], [2, 3]] + + Find minimum spanning edges by Prim's algorithm + + >>> G = nx.cycle_graph(4) + >>> G.add_edge(0, 3, weight=2) + >>> mst = tree.minimum_spanning_edges(G, algorithm="prim", data=False) + >>> edgelist = list(mst) + >>> sorted(sorted(e) for e in edgelist) + [[0, 1], [1, 2], [2, 3]] + + Notes + ----- + For Borůvka's algorithm, each edge must have a weight attribute, and + each edge weight must be distinct. + + For the other algorithms, if the graph edges do not have a weight + attribute a default weight of 1 will be used. + + Modified code from David Eppstein, April 2006 + http://www.ics.uci.edu/~eppstein/PADS/ + + """ + try: + algo = ALGORITHMS[algorithm] + except KeyError as err: + msg = f"{algorithm} is not a valid choice for an algorithm." + raise ValueError(msg) from err + + return algo( + G, minimum=True, weight=weight, keys=keys, data=data, ignore_nan=ignore_nan + ) + + +@not_implemented_for("directed") +@nx._dispatchable(edge_attrs="weight", preserve_edge_attrs="data") +def maximum_spanning_edges( + G, algorithm="kruskal", weight="weight", keys=True, data=True, ignore_nan=False +): + """Generate edges in a maximum spanning forest of an undirected + weighted graph. + + A maximum spanning tree is a subgraph of the graph (a tree) + with the maximum possible sum of edge weights. A spanning forest is a + union of the spanning trees for each connected component of the graph. + + Parameters + ---------- + G : undirected Graph + An undirected graph. If `G` is connected, then the algorithm finds a + spanning tree. Otherwise, a spanning forest is found. + + algorithm : string + The algorithm to use when finding a maximum spanning tree. Valid + choices are 'kruskal', 'prim', or 'boruvka'. The default is 'kruskal'. + + weight : string + Edge data key to use for weight (default 'weight'). + + keys : bool + Whether to yield edge key in multigraphs in addition to the edge. + If `G` is not a multigraph, this is ignored. + + data : bool, optional + If True yield the edge data along with the edge. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + Returns + ------- + edges : iterator + An iterator over edges in a maximum spanning tree of `G`. + Edges connecting nodes `u` and `v` are represented as tuples: + `(u, v, k, d)` or `(u, v, k)` or `(u, v, d)` or `(u, v)` + + If `G` is a multigraph, `keys` indicates whether the edge key `k` will + be reported in the third position in the edge tuple. `data` indicates + whether the edge datadict `d` will appear at the end of the edge tuple. + + If `G` is not a multigraph, the tuples are `(u, v, d)` if `data` is True + or `(u, v)` if `data` is False. + + Examples + -------- + >>> from networkx.algorithms import tree + + Find maximum spanning edges by Kruskal's algorithm + + >>> G = nx.cycle_graph(4) + >>> G.add_edge(0, 3, weight=2) + >>> mst = tree.maximum_spanning_edges(G, algorithm="kruskal", data=False) + >>> edgelist = list(mst) + >>> sorted(sorted(e) for e in edgelist) + [[0, 1], [0, 3], [1, 2]] + + Find maximum spanning edges by Prim's algorithm + + >>> G = nx.cycle_graph(4) + >>> G.add_edge(0, 3, weight=2) # assign weight 2 to edge 0-3 + >>> mst = tree.maximum_spanning_edges(G, algorithm="prim", data=False) + >>> edgelist = list(mst) + >>> sorted(sorted(e) for e in edgelist) + [[0, 1], [0, 3], [2, 3]] + + Notes + ----- + For Borůvka's algorithm, each edge must have a weight attribute, and + each edge weight must be distinct. + + For the other algorithms, if the graph edges do not have a weight + attribute a default weight of 1 will be used. + + Modified code from David Eppstein, April 2006 + http://www.ics.uci.edu/~eppstein/PADS/ + """ + try: + algo = ALGORITHMS[algorithm] + except KeyError as err: + msg = f"{algorithm} is not a valid choice for an algorithm." + raise ValueError(msg) from err + + return algo( + G, minimum=False, weight=weight, keys=keys, data=data, ignore_nan=ignore_nan + ) + + +@nx._dispatchable(preserve_all_attrs=True, returns_graph=True) +def minimum_spanning_tree(G, weight="weight", algorithm="kruskal", ignore_nan=False): + """Returns a minimum spanning tree or forest on an undirected graph `G`. + + Parameters + ---------- + G : undirected graph + An undirected graph. If `G` is connected, then the algorithm finds a + spanning tree. Otherwise, a spanning forest is found. + + weight : str + Data key to use for edge weights. + + algorithm : string + The algorithm to use when finding a minimum spanning tree. Valid + choices are 'kruskal', 'prim', or 'boruvka'. The default is + 'kruskal'. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + Returns + ------- + G : NetworkX Graph + A minimum spanning tree or forest. + + Examples + -------- + >>> G = nx.cycle_graph(4) + >>> G.add_edge(0, 3, weight=2) + >>> T = nx.minimum_spanning_tree(G) + >>> sorted(T.edges(data=True)) + [(0, 1, {}), (1, 2, {}), (2, 3, {})] + + + Notes + ----- + For Borůvka's algorithm, each edge must have a weight attribute, and + each edge weight must be distinct. + + For the other algorithms, if the graph edges do not have a weight + attribute a default weight of 1 will be used. + + There may be more than one tree with the same minimum or maximum weight. + See :mod:`networkx.tree.recognition` for more detailed definitions. + + Isolated nodes with self-loops are in the tree as edgeless isolated nodes. + + """ + edges = minimum_spanning_edges( + G, algorithm, weight, keys=True, data=True, ignore_nan=ignore_nan + ) + T = G.__class__() # Same graph class as G + T.graph.update(G.graph) + T.add_nodes_from(G.nodes.items()) + T.add_edges_from(edges) + return T + + +@nx._dispatchable(preserve_all_attrs=True, returns_graph=True) +def partition_spanning_tree( + G, minimum=True, weight="weight", partition="partition", ignore_nan=False +): + """ + Find a spanning tree while respecting a partition of edges. + + Edges can be flagged as either `INCLUDED` which are required to be in the + returned tree, `EXCLUDED`, which cannot be in the returned tree and `OPEN`. + + This is used in the SpanningTreeIterator to create new partitions following + the algorithm of Sörensen and Janssens [1]_. + + Parameters + ---------- + G : undirected graph + An undirected graph. + + minimum : bool (default: True) + Determines whether the returned tree is the minimum spanning tree of + the partition of the maximum one. + + weight : str + Data key to use for edge weights. + + partition : str + The key for the edge attribute containing the partition + data on the graph. Edges can be included, excluded or open using the + `EdgePartition` enum. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + + Returns + ------- + G : NetworkX Graph + A minimum spanning tree using all of the included edges in the graph and + none of the excluded edges. + + References + ---------- + .. [1] G.K. Janssens, K. Sörensen, An algorithm to generate all spanning + trees in order of increasing cost, Pesquisa Operacional, 2005-08, + Vol. 25 (2), p. 219-229, + https://www.scielo.br/j/pope/a/XHswBwRwJyrfL88dmMwYNWp/?lang=en + """ + edges = kruskal_mst_edges( + G, + minimum, + weight, + keys=True, + data=True, + ignore_nan=ignore_nan, + partition=partition, + ) + T = G.__class__() # Same graph class as G + T.graph.update(G.graph) + T.add_nodes_from(G.nodes.items()) + T.add_edges_from(edges) + return T + + +@nx._dispatchable(preserve_all_attrs=True, returns_graph=True) +def maximum_spanning_tree(G, weight="weight", algorithm="kruskal", ignore_nan=False): + """Returns a maximum spanning tree or forest on an undirected graph `G`. + + Parameters + ---------- + G : undirected graph + An undirected graph. If `G` is connected, then the algorithm finds a + spanning tree. Otherwise, a spanning forest is found. + + weight : str + Data key to use for edge weights. + + algorithm : string + The algorithm to use when finding a maximum spanning tree. Valid + choices are 'kruskal', 'prim', or 'boruvka'. The default is + 'kruskal'. + + ignore_nan : bool (default: False) + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + + + Returns + ------- + G : NetworkX Graph + A maximum spanning tree or forest. + + + Examples + -------- + >>> G = nx.cycle_graph(4) + >>> G.add_edge(0, 3, weight=2) + >>> T = nx.maximum_spanning_tree(G) + >>> sorted(T.edges(data=True)) + [(0, 1, {}), (0, 3, {'weight': 2}), (1, 2, {})] + + + Notes + ----- + For Borůvka's algorithm, each edge must have a weight attribute, and + each edge weight must be distinct. + + For the other algorithms, if the graph edges do not have a weight + attribute a default weight of 1 will be used. + + There may be more than one tree with the same minimum or maximum weight. + See :mod:`networkx.tree.recognition` for more detailed definitions. + + Isolated nodes with self-loops are in the tree as edgeless isolated nodes. + + """ + edges = maximum_spanning_edges( + G, algorithm, weight, keys=True, data=True, ignore_nan=ignore_nan + ) + edges = list(edges) + T = G.__class__() # Same graph class as G + T.graph.update(G.graph) + T.add_nodes_from(G.nodes.items()) + T.add_edges_from(edges) + return T + + +@py_random_state(3) +@nx._dispatchable(preserve_edge_attrs=True, returns_graph=True) +def random_spanning_tree(G, weight=None, *, multiplicative=True, seed=None): + """ + Sample a random spanning tree using the edges weights of `G`. + + This function supports two different methods for determining the + probability of the graph. If ``multiplicative=True``, the probability + is based on the product of edge weights, and if ``multiplicative=False`` + it is based on the sum of the edge weight. However, since it is + easier to determine the total weight of all spanning trees for the + multiplicative version, that is significantly faster and should be used if + possible. Additionally, setting `weight` to `None` will cause a spanning tree + to be selected with uniform probability. + + The function uses algorithm A8 in [1]_ . + + Parameters + ---------- + G : nx.Graph + An undirected version of the original graph. + + weight : string + The edge key for the edge attribute holding edge weight. + + multiplicative : bool, default=True + If `True`, the probability of each tree is the product of its edge weight + over the sum of the product of all the spanning trees in the graph. If + `False`, the probability is the sum of its edge weight over the sum of + the sum of weights for all spanning trees in the graph. + + seed : integer, random_state, or None (default) + Indicator of random number generation state. + See :ref:`Randomness`. + + Returns + ------- + nx.Graph + A spanning tree using the distribution defined by the weight of the tree. + + References + ---------- + .. [1] V. Kulkarni, Generating random combinatorial objects, Journal of + Algorithms, 11 (1990), pp. 185–207 + """ + + def find_node(merged_nodes, node): + """ + We can think of clusters of contracted nodes as having one + representative in the graph. Each node which is not in merged_nodes + is still its own representative. Since a representative can be later + contracted, we need to recursively search though the dict to find + the final representative, but once we know it we can use path + compression to speed up the access of the representative for next time. + + This cannot be replaced by the standard NetworkX union_find since that + data structure will merge nodes with less representing nodes into the + one with more representing nodes but this function requires we merge + them using the order that contract_edges contracts using. + + Parameters + ---------- + merged_nodes : dict + The dict storing the mapping from node to representative + node + The node whose representative we seek + + Returns + ------- + The representative of the `node` + """ + if node not in merged_nodes: + return node + else: + rep = find_node(merged_nodes, merged_nodes[node]) + merged_nodes[node] = rep + return rep + + def prepare_graph(): + """ + For the graph `G`, remove all edges not in the set `V` and then + contract all edges in the set `U`. + + Returns + ------- + A copy of `G` which has had all edges not in `V` removed and all edges + in `U` contracted. + """ + + # The result is a MultiGraph version of G so that parallel edges are + # allowed during edge contraction + result = nx.MultiGraph(incoming_graph_data=G) + + # Remove all edges not in V + edges_to_remove = set(result.edges()).difference(V) + result.remove_edges_from(edges_to_remove) + + # Contract all edges in U + # + # Imagine that you have two edges to contract and they share an + # endpoint like this: + # [0] ----- [1] ----- [2] + # If we contract (0, 1) first, the contraction function will always + # delete the second node it is passed so the resulting graph would be + # [0] ----- [2] + # and edge (1, 2) no longer exists but (0, 2) would need to be contracted + # in its place now. That is why I use the below dict as a merge-find + # data structure with path compression to track how the nodes are merged. + merged_nodes = {} + + for u, v in U: + u_rep = find_node(merged_nodes, u) + v_rep = find_node(merged_nodes, v) + # We cannot contract a node with itself + if u_rep == v_rep: + continue + nx.contracted_nodes(result, u_rep, v_rep, self_loops=False, copy=False) + merged_nodes[v_rep] = u_rep + + return merged_nodes, result + + def spanning_tree_total_weight(G, weight): + """ + Find the sum of weights of the spanning trees of `G` using the + appropriate `method`. + + This is easy if the chosen method is 'multiplicative', since we can + use Kirchhoff's Tree Matrix Theorem directly. However, with the + 'additive' method, this process is slightly more complex and less + computationally efficient as we have to find the number of spanning + trees which contain each possible edge in the graph. + + Parameters + ---------- + G : NetworkX Graph + The graph to find the total weight of all spanning trees on. + + weight : string + The key for the weight edge attribute of the graph. + + Returns + ------- + float + The sum of either the multiplicative or additive weight for all + spanning trees in the graph. + """ + if multiplicative: + return nx.total_spanning_tree_weight(G, weight) + else: + # There are two cases for the total spanning tree additive weight. + # 1. There is one edge in the graph. Then the only spanning tree is + # that edge itself, which will have a total weight of that edge + # itself. + if G.number_of_edges() == 1: + return G.edges(data=weight).__iter__().__next__()[2] + # 2. There are no edges or two or more edges in the graph. Then, we find the + # total weight of the spanning trees using the formula in the + # reference paper: take the weight of each edge and multiply it by + # the number of spanning trees which include that edge. This + # can be accomplished by contracting the edge and finding the + # multiplicative total spanning tree weight if the weight of each edge + # is assumed to be 1, which is conveniently built into networkx already, + # by calling total_spanning_tree_weight with weight=None. + # Note that with no edges the returned value is just zero. + else: + total = 0 + for u, v, w in G.edges(data=weight): + total += w * nx.total_spanning_tree_weight( + nx.contracted_edge(G, edge=(u, v), self_loops=False), None + ) + return total + + if G.number_of_nodes() < 2: + # no edges in the spanning tree + return nx.empty_graph(G.nodes) + + U = set() + st_cached_value = 0 + V = set(G.edges()) + shuffled_edges = list(G.edges()) + seed.shuffle(shuffled_edges) + + for u, v in shuffled_edges: + e_weight = G[u][v][weight] if weight is not None else 1 + node_map, prepared_G = prepare_graph() + G_total_tree_weight = spanning_tree_total_weight(prepared_G, weight) + # Add the edge to U so that we can compute the total tree weight + # assuming we include that edge + # Now, if (u, v) cannot exist in G because it is fully contracted out + # of existence, then it by definition cannot influence G_e's Kirchhoff + # value. But, we also cannot pick it. + rep_edge = (find_node(node_map, u), find_node(node_map, v)) + # Check to see if the 'representative edge' for the current edge is + # in prepared_G. If so, then we can pick it. + if rep_edge in prepared_G.edges: + prepared_G_e = nx.contracted_edge( + prepared_G, edge=rep_edge, self_loops=False + ) + G_e_total_tree_weight = spanning_tree_total_weight(prepared_G_e, weight) + if multiplicative: + threshold = e_weight * G_e_total_tree_weight / G_total_tree_weight + else: + numerator = ( + st_cached_value + e_weight + ) * nx.total_spanning_tree_weight(prepared_G_e) + G_e_total_tree_weight + denominator = ( + st_cached_value * nx.total_spanning_tree_weight(prepared_G) + + G_total_tree_weight + ) + threshold = numerator / denominator + else: + threshold = 0.0 + z = seed.uniform(0.0, 1.0) + if z > threshold: + # Remove the edge from V since we did not pick it. + V.remove((u, v)) + else: + # Add the edge to U since we picked it. + st_cached_value += e_weight + U.add((u, v)) + # If we decide to keep an edge, it may complete the spanning tree. + if len(U) == G.number_of_nodes() - 1: + spanning_tree = nx.Graph() + spanning_tree.add_edges_from(U) + return spanning_tree + raise Exception(f"Something went wrong! Only {len(U)} edges in the spanning tree!") + + +class SpanningTreeIterator: + """ + Iterate over all spanning trees of a graph in either increasing or + decreasing cost. + + Notes + ----- + This iterator uses the partition scheme from [1]_ (included edges, + excluded edges and open edges) as well as a modified Kruskal's Algorithm + to generate minimum spanning trees which respect the partition of edges. + For spanning trees with the same weight, ties are broken arbitrarily. + + References + ---------- + .. [1] G.K. Janssens, K. Sörensen, An algorithm to generate all spanning + trees in order of increasing cost, Pesquisa Operacional, 2005-08, + Vol. 25 (2), p. 219-229, + https://www.scielo.br/j/pope/a/XHswBwRwJyrfL88dmMwYNWp/?lang=en + """ + + @dataclass(order=True) + class Partition: + """ + This dataclass represents a partition and stores a dict with the edge + data and the weight of the minimum spanning tree of the partition dict. + """ + + mst_weight: float + partition_dict: dict = field(compare=False) + + def __copy__(self): + return SpanningTreeIterator.Partition( + self.mst_weight, self.partition_dict.copy() + ) + + def __init__(self, G, weight="weight", minimum=True, ignore_nan=False): + """ + Initialize the iterator + + Parameters + ---------- + G : nx.Graph + The directed graph which we need to iterate trees over + + weight : String, default = "weight" + The edge attribute used to store the weight of the edge + + minimum : bool, default = True + Return the trees in increasing order while true and decreasing order + while false. + + ignore_nan : bool, default = False + If a NaN is found as an edge weight normally an exception is raised. + If `ignore_nan is True` then that edge is ignored instead. + """ + self.G = G.copy() + self.G.__networkx_cache__ = None # Disable caching + self.weight = weight + self.minimum = minimum + self.ignore_nan = ignore_nan + # Randomly create a key for an edge attribute to hold the partition data + self.partition_key = ( + "SpanningTreeIterators super secret partition attribute name" + ) + + def __iter__(self): + """ + Returns + ------- + SpanningTreeIterator + The iterator object for this graph + """ + self.partition_queue = PriorityQueue() + self._clear_partition(self.G) + mst_weight = partition_spanning_tree( + self.G, self.minimum, self.weight, self.partition_key, self.ignore_nan + ).size(weight=self.weight) + + self.partition_queue.put( + self.Partition(mst_weight if self.minimum else -mst_weight, {}) + ) + + return self + + def __next__(self): + """ + Returns + ------- + (multi)Graph + The spanning tree of next greatest weight, which ties broken + arbitrarily. + """ + if self.partition_queue.empty(): + del self.G, self.partition_queue + raise StopIteration + + partition = self.partition_queue.get() + self._write_partition(partition) + next_tree = partition_spanning_tree( + self.G, self.minimum, self.weight, self.partition_key, self.ignore_nan + ) + self._partition(partition, next_tree) + + self._clear_partition(next_tree) + return next_tree + + def _partition(self, partition, partition_tree): + """ + Create new partitions based of the minimum spanning tree of the + current minimum partition. + + Parameters + ---------- + partition : Partition + The Partition instance used to generate the current minimum spanning + tree. + partition_tree : nx.Graph + The minimum spanning tree of the input partition. + """ + # create two new partitions with the data from the input partition dict + p1 = self.Partition(0, partition.partition_dict.copy()) + p2 = self.Partition(0, partition.partition_dict.copy()) + for e in partition_tree.edges: + # determine if the edge was open or included + if e not in partition.partition_dict: + # This is an open edge + p1.partition_dict[e] = EdgePartition.EXCLUDED + p2.partition_dict[e] = EdgePartition.INCLUDED + + self._write_partition(p1) + p1_mst = partition_spanning_tree( + self.G, + self.minimum, + self.weight, + self.partition_key, + self.ignore_nan, + ) + p1_mst_weight = p1_mst.size(weight=self.weight) + if nx.is_connected(p1_mst): + p1.mst_weight = p1_mst_weight if self.minimum else -p1_mst_weight + self.partition_queue.put(p1.__copy__()) + p1.partition_dict = p2.partition_dict.copy() + + def _write_partition(self, partition): + """ + Writes the desired partition into the graph to calculate the minimum + spanning tree. + + Parameters + ---------- + partition : Partition + A Partition dataclass describing a partition on the edges of the + graph. + """ + + partition_dict = partition.partition_dict + partition_key = self.partition_key + G = self.G + + edges = ( + G.edges(keys=True, data=True) if G.is_multigraph() else G.edges(data=True) + ) + for *e, d in edges: + d[partition_key] = partition_dict.get(tuple(e), EdgePartition.OPEN) + + def _clear_partition(self, G): + """ + Removes partition data from the graph + """ + partition_key = self.partition_key + edges = ( + G.edges(keys=True, data=True) if G.is_multigraph() else G.edges(data=True) + ) + for *e, d in edges: + if partition_key in d: + del d[partition_key] + + +@nx._dispatchable(edge_attrs="weight") +def number_of_spanning_trees(G, *, root=None, weight=None): + """Returns the number of spanning trees in `G`. + + A spanning tree for an undirected graph is a tree that connects + all nodes in the graph. For a directed graph, the analog of a + spanning tree is called a (spanning) arborescence. The arborescence + includes a unique directed path from the `root` node to each other node. + The graph must be weakly connected, and the root must be a node + that includes all nodes as successors [3]_. Note that to avoid + discussing sink-roots and reverse-arborescences, we have reversed + the edge orientation from [3]_ and use the in-degree laplacian. + + This function (when `weight` is `None`) returns the number of + spanning trees for an undirected graph and the number of + arborescences from a single root node for a directed graph. + When `weight` is the name of an edge attribute which holds the + weight value of each edge, the function returns the sum over + all trees of the multiplicative weight of each tree. That is, + the weight of the tree is the product of its edge weights. + + Kirchoff's Tree Matrix Theorem states that any cofactor of the + Laplacian matrix of a graph is the number of spanning trees in the + graph. (Here we use cofactors for a diagonal entry so that the + cofactor becomes the determinant of the matrix with one row + and its matching column removed.) For a weighted Laplacian matrix, + the cofactor is the sum across all spanning trees of the + multiplicative weight of each tree. That is, the weight of each + tree is the product of its edge weights. The theorem is also + known as Kirchhoff's theorem [1]_ and the Matrix-Tree theorem [2]_. + + For directed graphs, a similar theorem (Tutte's Theorem) holds with + the cofactor chosen to be the one with row and column removed that + correspond to the root. The cofactor is the number of arborescences + with the specified node as root. And the weighted version gives the + sum of the arborescence weights with root `root`. The arborescence + weight is the product of its edge weights. + + Parameters + ---------- + G : NetworkX graph + + root : node + A node in the directed graph `G` that has all nodes as descendants. + (This is ignored for undirected graphs.) + + weight : string or None, optional (default=None) + The name of the edge attribute holding the edge weight. + If `None`, then each edge is assumed to have a weight of 1. + + Returns + ------- + Number + Undirected graphs: + The number of spanning trees of the graph `G`. + Or the sum of all spanning tree weights of the graph `G` + where the weight of a tree is the product of its edge weights. + Directed graphs: + The number of arborescences of `G` rooted at node `root`. + Or the sum of all arborescence weights of the graph `G` with + specified root where the weight of an arborescence is the product + of its edge weights. + + Raises + ------ + NetworkXPointlessConcept + If `G` does not contain any nodes. + + NetworkXError + If the graph `G` is directed and the root node + is not specified or is not in G. + + Examples + -------- + >>> G = nx.complete_graph(5) + >>> round(nx.number_of_spanning_trees(G)) + 125 + + >>> G = nx.Graph() + >>> G.add_edge(1, 2, weight=2) + >>> G.add_edge(1, 3, weight=1) + >>> G.add_edge(2, 3, weight=1) + >>> round(nx.number_of_spanning_trees(G, weight="weight")) + 5 + + Notes + ----- + Self-loops are excluded. Multi-edges are contracted in one edge + equal to the sum of the weights. + + References + ---------- + .. [1] Wikipedia + "Kirchhoff's theorem." + https://en.wikipedia.org/wiki/Kirchhoff%27s_theorem + .. [2] Kirchhoff, G. R. + Über die Auflösung der Gleichungen, auf welche man + bei der Untersuchung der linearen Vertheilung + Galvanischer Ströme geführt wird + Annalen der Physik und Chemie, vol. 72, pp. 497-508, 1847. + .. [3] Margoliash, J. + "Matrix-Tree Theorem for Directed Graphs" + https://www.math.uchicago.edu/~may/VIGRE/VIGRE2010/REUPapers/Margoliash.pdf + """ + import numpy as np + + if len(G) == 0: + raise nx.NetworkXPointlessConcept("Graph G must contain at least one node.") + + # undirected G + if not nx.is_directed(G): + if not nx.is_connected(G): + return 0 + G_laplacian = nx.laplacian_matrix(G, weight=weight).toarray() + return float(np.linalg.det(G_laplacian[1:, 1:])) + + # directed G + if root is None: + raise nx.NetworkXError("Input `root` must be provided when G is directed") + if root not in G: + raise nx.NetworkXError("The node root is not in the graph G.") + if not nx.is_weakly_connected(G): + return 0 + + # Compute directed Laplacian matrix + nodelist = [root] + [n for n in G if n != root] + A = nx.adjacency_matrix(G, nodelist=nodelist, weight=weight) + D = np.diag(A.sum(axis=0)) + G_laplacian = D - A + + # Compute number of spanning trees + return float(np.linalg.det(G_laplacian[1:, 1:])) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/operations.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/operations.py new file mode 100644 index 0000000000000000000000000000000000000000..6c3e839453e686c80d33c94a66defa87698a066f --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/operations.py @@ -0,0 +1,105 @@ +"""Operations on trees.""" + +from functools import partial +from itertools import accumulate, chain + +import networkx as nx + +__all__ = ["join_trees"] + + +# Argument types don't match dispatching, but allow manual selection of backend +@nx._dispatchable(graphs=None, returns_graph=True) +def join_trees(rooted_trees, *, label_attribute=None, first_label=0): + """Returns a new rooted tree made by joining `rooted_trees` + + Constructs a new tree by joining each tree in `rooted_trees`. + A new root node is added and connected to each of the roots + of the input trees. While copying the nodes from the trees, + relabeling to integers occurs. If the `label_attribute` is provided, + the old node labels will be stored in the new tree under this attribute. + + Parameters + ---------- + rooted_trees : list + A list of pairs in which each left element is a NetworkX graph + object representing a tree and each right element is the root + node of that tree. The nodes of these trees will be relabeled to + integers. + + label_attribute : str + If provided, the old node labels will be stored in the new tree + under this node attribute. If not provided, the original labels + of the nodes in the input trees are not stored. + + first_label : int, optional (default=0) + Specifies the label for the new root node. If provided, the root node of the joined tree + will have this label. If not provided, the root node will default to a label of 0. + + Returns + ------- + NetworkX graph + The rooted tree resulting from joining the provided `rooted_trees`. The new tree has a root node + labeled as specified by `first_label` (defaulting to 0 if not provided). Subtrees from the input + `rooted_trees` are attached to this new root node. Each non-root node, if the `label_attribute` + is provided, has an attribute that indicates the original label of the node in the input tree. + + Notes + ----- + Trees are stored in NetworkX as NetworkX Graphs. There is no specific + enforcement of the fact that these are trees. Testing for each tree + can be done using :func:`networkx.is_tree`. + + Graph, edge, and node attributes are propagated from the given + rooted trees to the created tree. If there are any overlapping graph + attributes, those from later trees will overwrite those from earlier + trees in the tuple of positional arguments. + + Examples + -------- + Join two full balanced binary trees of height *h* to get a full + balanced binary tree of depth *h* + 1:: + + >>> h = 4 + >>> left = nx.balanced_tree(2, h) + >>> right = nx.balanced_tree(2, h) + >>> joined_tree = nx.join_trees([(left, 0), (right, 0)]) + >>> nx.is_isomorphic(joined_tree, nx.balanced_tree(2, h + 1)) + True + + """ + if not rooted_trees: + return nx.empty_graph(1) + + # Unzip the zipped list of (tree, root) pairs. + trees, roots = zip(*rooted_trees) + + # The join of the trees has the same type as the type of the first tree. + R = type(trees[0])() + + lengths = (len(tree) for tree in trees[:-1]) + first_labels = list(accumulate(lengths, initial=first_label + 1)) + + new_roots = [] + for tree, root, first_node in zip(trees, roots, first_labels): + new_root = first_node + list(tree.nodes()).index(root) + new_roots.append(new_root) + + # Relabel the nodes so that their union is the integers starting at first_label. + relabel = partial( + nx.convert_node_labels_to_integers, label_attribute=label_attribute + ) + new_trees = [ + relabel(tree, first_label=first_label) + for tree, first_label in zip(trees, first_labels) + ] + + # Add all sets of nodes and edges, attributes + for tree in new_trees: + R.update(tree) + + # Finally, join the subtrees at the root. We know first_label is unused by the way we relabeled the subtrees. + R.add_node(first_label) + R.add_edges_from((first_label, root) for root in new_roots) + + return R diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/recognition.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/recognition.py new file mode 100644 index 0000000000000000000000000000000000000000..a9eae98707a6889213ff8b93887c481ba59215a0 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/recognition.py @@ -0,0 +1,273 @@ +""" +Recognition Tests +================= + +A *forest* is an acyclic, undirected graph, and a *tree* is a connected forest. +Depending on the subfield, there are various conventions for generalizing these +definitions to directed graphs. + +In one convention, directed variants of forest and tree are defined in an +identical manner, except that the direction of the edges is ignored. In effect, +each directed edge is treated as a single undirected edge. Then, additional +restrictions are imposed to define *branchings* and *arborescences*. + +In another convention, directed variants of forest and tree correspond to +the previous convention's branchings and arborescences, respectively. Then two +new terms, *polyforest* and *polytree*, are defined to correspond to the other +convention's forest and tree. + +Summarizing:: + + +-----------------------------+ + | Convention A | Convention B | + +=============================+ + | forest | polyforest | + | tree | polytree | + | branching | forest | + | arborescence | tree | + +-----------------------------+ + +Each convention has its reasons. The first convention emphasizes definitional +similarity in that directed forests and trees are only concerned with +acyclicity and do not have an in-degree constraint, just as their undirected +counterparts do not. The second convention emphasizes functional similarity +in the sense that the directed analog of a spanning tree is a spanning +arborescence. That is, take any spanning tree and choose one node as the root. +Then every edge is assigned a direction such there is a directed path from the +root to every other node. The result is a spanning arborescence. + +NetworkX follows convention "A". Explicitly, these are: + +undirected forest + An undirected graph with no undirected cycles. + +undirected tree + A connected, undirected forest. + +directed forest + A directed graph with no undirected cycles. Equivalently, the underlying + graph structure (which ignores edge orientations) is an undirected forest. + In convention B, this is known as a polyforest. + +directed tree + A weakly connected, directed forest. Equivalently, the underlying graph + structure (which ignores edge orientations) is an undirected tree. In + convention B, this is known as a polytree. + +branching + A directed forest with each node having, at most, one parent. So the maximum + in-degree is equal to 1. In convention B, this is known as a forest. + +arborescence + A directed tree with each node having, at most, one parent. So the maximum + in-degree is equal to 1. In convention B, this is known as a tree. + +For trees and arborescences, the adjective "spanning" may be added to designate +that the graph, when considered as a forest/branching, consists of a single +tree/arborescence that includes all nodes in the graph. It is true, by +definition, that every tree/arborescence is spanning with respect to the nodes +that define the tree/arborescence and so, it might seem redundant to introduce +the notion of "spanning". However, the nodes may represent a subset of +nodes from a larger graph, and it is in this context that the term "spanning" +becomes a useful notion. + +""" + +import networkx as nx + +__all__ = ["is_arborescence", "is_branching", "is_forest", "is_tree"] + + +@nx.utils.not_implemented_for("undirected") +@nx._dispatchable +def is_arborescence(G): + """ + Returns True if `G` is an arborescence. + + An arborescence is a directed tree with maximum in-degree equal to 1. + + Parameters + ---------- + G : graph + The graph to test. + + Returns + ------- + b : bool + A boolean that is True if `G` is an arborescence. + + Examples + -------- + >>> G = nx.DiGraph([(0, 1), (0, 2), (2, 3), (3, 4)]) + >>> nx.is_arborescence(G) + True + >>> G.remove_edge(0, 1) + >>> G.add_edge(1, 2) # maximum in-degree is 2 + >>> nx.is_arborescence(G) + False + + Notes + ----- + In another convention, an arborescence is known as a *tree*. + + See Also + -------- + is_tree + + """ + return is_tree(G) and max(d for n, d in G.in_degree()) <= 1 + + +@nx.utils.not_implemented_for("undirected") +@nx._dispatchable +def is_branching(G): + """ + Returns True if `G` is a branching. + + A branching is a directed forest with maximum in-degree equal to 1. + + Parameters + ---------- + G : directed graph + The directed graph to test. + + Returns + ------- + b : bool + A boolean that is True if `G` is a branching. + + Examples + -------- + >>> G = nx.DiGraph([(0, 1), (1, 2), (2, 3), (3, 4)]) + >>> nx.is_branching(G) + True + >>> G.remove_edge(2, 3) + >>> G.add_edge(3, 1) # maximum in-degree is 2 + >>> nx.is_branching(G) + False + + Notes + ----- + In another convention, a branching is also known as a *forest*. + + See Also + -------- + is_forest + + """ + return is_forest(G) and max(d for n, d in G.in_degree()) <= 1 + + +@nx._dispatchable +def is_forest(G): + """ + Returns True if `G` is a forest. + + A forest is a graph with no undirected cycles. + + For directed graphs, `G` is a forest if the underlying graph is a forest. + The underlying graph is obtained by treating each directed edge as a single + undirected edge in a multigraph. + + Parameters + ---------- + G : graph + The graph to test. + + Returns + ------- + b : bool + A boolean that is True if `G` is a forest. + + Raises + ------ + NetworkXPointlessConcept + If `G` is empty. + + Examples + -------- + >>> G = nx.Graph() + >>> G.add_edges_from([(1, 2), (1, 3), (2, 4), (2, 5)]) + >>> nx.is_forest(G) + True + >>> G.add_edge(4, 1) + >>> nx.is_forest(G) + False + + Notes + ----- + In another convention, a directed forest is known as a *polyforest* and + then *forest* corresponds to a *branching*. + + See Also + -------- + is_branching + + """ + if len(G) == 0: + raise nx.exception.NetworkXPointlessConcept("G has no nodes.") + + if G.is_directed(): + components = (G.subgraph(c) for c in nx.weakly_connected_components(G)) + else: + components = (G.subgraph(c) for c in nx.connected_components(G)) + + return all(len(c) - 1 == c.number_of_edges() for c in components) + + +@nx._dispatchable +def is_tree(G): + """ + Returns True if `G` is a tree. + + A tree is a connected graph with no undirected cycles. + + For directed graphs, `G` is a tree if the underlying graph is a tree. The + underlying graph is obtained by treating each directed edge as a single + undirected edge in a multigraph. + + Parameters + ---------- + G : graph + The graph to test. + + Returns + ------- + b : bool + A boolean that is True if `G` is a tree. + + Raises + ------ + NetworkXPointlessConcept + If `G` is empty. + + Examples + -------- + >>> G = nx.Graph() + >>> G.add_edges_from([(1, 2), (1, 3), (2, 4), (2, 5)]) + >>> nx.is_tree(G) # n-1 edges + True + >>> G.add_edge(3, 4) + >>> nx.is_tree(G) # n edges + False + + Notes + ----- + In another convention, a directed tree is known as a *polytree* and then + *tree* corresponds to an *arborescence*. + + See Also + -------- + is_arborescence + + """ + if len(G) == 0: + raise nx.exception.NetworkXPointlessConcept("G has no nodes.") + + if G.is_directed(): + is_connected = nx.is_weakly_connected + else: + is_connected = nx.is_connected + + # A connected graph with no cycles has n-1 edges. + return len(G) - 1 == G.number_of_edges() and is_connected(G) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/__init__.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/__init__.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..a4bd1f5a946424420875aca8fb87a40eff30da2a Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/__init__.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_branchings.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_branchings.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..0af00914a9a678f4da19be21afc197caf0b44f3a Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_branchings.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_decomposition.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_decomposition.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..d27b277db131f1d329c7d0f7a6baa090d93863b2 Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_decomposition.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_mst.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_mst.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..26ed3abb26d06bcd7b3b5bf68c9d76d961898dbb Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_mst.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_operations.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_operations.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..48621aa0968ecb238544ab07b8d8fa397e4af10f Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_operations.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_recognition.cpython-310.pyc b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_recognition.cpython-310.pyc new file mode 100644 index 0000000000000000000000000000000000000000..08655d33ce16cfa63c3f25e85a058a4c0e0c800d Binary files /dev/null and b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/__pycache__/test_recognition.cpython-310.pyc differ diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_branchings.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_branchings.py new file mode 100644 index 0000000000000000000000000000000000000000..e19ddee332b93d8131d48fa7cfc837625b2261f4 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_branchings.py @@ -0,0 +1,624 @@ +import math +from operator import itemgetter + +import pytest + +np = pytest.importorskip("numpy") + +import networkx as nx +from networkx.algorithms.tree import branchings, recognition + +# +# Explicitly discussed examples from Edmonds paper. +# + +# Used in Figures A-F. +# +# fmt: off +G_array = np.array([ + # 0 1 2 3 4 5 6 7 8 + [0, 0, 12, 0, 12, 0, 0, 0, 0], # 0 + [4, 0, 0, 0, 0, 13, 0, 0, 0], # 1 + [0, 17, 0, 21, 0, 12, 0, 0, 0], # 2 + [5, 0, 0, 0, 17, 0, 18, 0, 0], # 3 + [0, 0, 0, 0, 0, 0, 0, 12, 0], # 4 + [0, 0, 0, 0, 0, 0, 14, 0, 12], # 5 + [0, 0, 21, 0, 0, 0, 0, 0, 15], # 6 + [0, 0, 0, 19, 0, 0, 15, 0, 0], # 7 + [0, 0, 0, 0, 0, 0, 0, 18, 0], # 8 +], dtype=int) + +# Two copies of the graph from the original paper as disconnected components +G_big_array = np.zeros(np.array(G_array.shape) * 2, dtype=int) +G_big_array[:G_array.shape[0], :G_array.shape[1]] = G_array +G_big_array[G_array.shape[0]:, G_array.shape[1]:] = G_array + +# fmt: on + + +def G1(): + G = nx.from_numpy_array(G_array, create_using=nx.MultiDiGraph) + return G + + +def G2(): + # Now we shift all the weights by -10. + # Should not affect optimal arborescence, but does affect optimal branching. + Garr = G_array.copy() + Garr[np.nonzero(Garr)] -= 10 + G = nx.from_numpy_array(Garr, create_using=nx.MultiDiGraph) + return G + + +# An optimal branching for G1 that is also a spanning arborescence. So it is +# also an optimal spanning arborescence. +# +optimal_arborescence_1 = [ + (0, 2, 12), + (2, 1, 17), + (2, 3, 21), + (1, 5, 13), + (3, 4, 17), + (3, 6, 18), + (6, 8, 15), + (8, 7, 18), +] + +# For G2, the optimal branching of G1 (with shifted weights) is no longer +# an optimal branching, but it is still an optimal spanning arborescence +# (just with shifted weights). An optimal branching for G2 is similar to what +# appears in figure G (this is greedy_subopt_branching_1a below), but with the +# edge (3, 0, 5), which is now (3, 0, -5), removed. Thus, the optimal branching +# is not a spanning arborescence. The code finds optimal_branching_2a. +# An alternative and equivalent branching is optimal_branching_2b. We would +# need to modify the code to iterate through all equivalent optimal branchings. +# +# These are maximal branchings or arborescences. +optimal_branching_2a = [ + (5, 6, 4), + (6, 2, 11), + (6, 8, 5), + (8, 7, 8), + (2, 1, 7), + (2, 3, 11), + (3, 4, 7), +] +optimal_branching_2b = [ + (8, 7, 8), + (7, 3, 9), + (3, 4, 7), + (3, 6, 8), + (6, 2, 11), + (2, 1, 7), + (1, 5, 3), +] +optimal_arborescence_2 = [ + (0, 2, 2), + (2, 1, 7), + (2, 3, 11), + (1, 5, 3), + (3, 4, 7), + (3, 6, 8), + (6, 8, 5), + (8, 7, 8), +] + +# Two suboptimal maximal branchings on G1 obtained from a greedy algorithm. +# 1a matches what is shown in Figure G in Edmonds's paper. +greedy_subopt_branching_1a = [ + (5, 6, 14), + (6, 2, 21), + (6, 8, 15), + (8, 7, 18), + (2, 1, 17), + (2, 3, 21), + (3, 0, 5), + (3, 4, 17), +] +greedy_subopt_branching_1b = [ + (8, 7, 18), + (7, 6, 15), + (6, 2, 21), + (2, 1, 17), + (2, 3, 21), + (1, 5, 13), + (3, 0, 5), + (3, 4, 17), +] + + +def build_branching(edges, double=False): + G = nx.DiGraph() + for u, v, weight in edges: + G.add_edge(u, v, weight=weight) + if double: + G.add_edge(u + 9, v + 9, weight=weight) + return G + + +def sorted_edges(G, attr="weight", default=1): + edges = [(u, v, data.get(attr, default)) for (u, v, data) in G.edges(data=True)] + edges = sorted(edges, key=lambda x: (x[2], x[1], x[0])) + return edges + + +def assert_equal_branchings(G1, G2, attr="weight", default=1): + edges1 = list(G1.edges(data=True)) + edges2 = list(G2.edges(data=True)) + assert len(edges1) == len(edges2) + + # Grab the weights only. + e1 = sorted_edges(G1, attr, default) + e2 = sorted_edges(G2, attr, default) + + for a, b in zip(e1, e2): + assert a[:2] == b[:2] + np.testing.assert_almost_equal(a[2], b[2]) + + +################ + + +def test_optimal_branching1(): + G = build_branching(optimal_arborescence_1) + assert recognition.is_arborescence(G), True + assert branchings.branching_weight(G) == 131 + + +def test_optimal_branching2a(): + G = build_branching(optimal_branching_2a) + assert recognition.is_arborescence(G), True + assert branchings.branching_weight(G) == 53 + + +def test_optimal_branching2b(): + G = build_branching(optimal_branching_2b) + assert recognition.is_arborescence(G), True + assert branchings.branching_weight(G) == 53 + + +def test_optimal_arborescence2(): + G = build_branching(optimal_arborescence_2) + assert recognition.is_arborescence(G), True + assert branchings.branching_weight(G) == 51 + + +def test_greedy_suboptimal_branching1a(): + G = build_branching(greedy_subopt_branching_1a) + assert recognition.is_arborescence(G), True + assert branchings.branching_weight(G) == 128 + + +def test_greedy_suboptimal_branching1b(): + G = build_branching(greedy_subopt_branching_1b) + assert recognition.is_arborescence(G), True + assert branchings.branching_weight(G) == 127 + + +def test_greedy_max1(): + # Standard test. + # + G = G1() + B = branchings.greedy_branching(G) + # There are only two possible greedy branchings. The sorting is such + # that it should equal the second suboptimal branching: 1b. + B_ = build_branching(greedy_subopt_branching_1b) + assert_equal_branchings(B, B_) + + +def test_greedy_branching_kwarg_kind(): + G = G1() + with pytest.raises(nx.NetworkXException, match="Unknown value for `kind`."): + B = branchings.greedy_branching(G, kind="lol") + + +def test_greedy_branching_for_unsortable_nodes(): + G = nx.DiGraph() + G.add_weighted_edges_from([((2, 3), 5, 1), (3, "a", 1), (2, 4, 5)]) + edges = [(u, v, data.get("weight", 1)) for (u, v, data) in G.edges(data=True)] + with pytest.raises(TypeError): + edges.sort(key=itemgetter(2, 0, 1), reverse=True) + B = branchings.greedy_branching(G, kind="max").edges(data=True) + assert list(B) == [ + ((2, 3), 5, {"weight": 1}), + (3, "a", {"weight": 1}), + (2, 4, {"weight": 5}), + ] + + +def test_greedy_max2(): + # Different default weight. + # + G = G1() + del G[1][0][0]["weight"] + B = branchings.greedy_branching(G, default=6) + # Chosen so that edge (3,0,5) is not selected and (1,0,6) is instead. + + edges = [ + (1, 0, 6), + (1, 5, 13), + (7, 6, 15), + (2, 1, 17), + (3, 4, 17), + (8, 7, 18), + (2, 3, 21), + (6, 2, 21), + ] + B_ = build_branching(edges) + assert_equal_branchings(B, B_) + + +def test_greedy_max3(): + # All equal weights. + # + G = G1() + B = branchings.greedy_branching(G, attr=None) + + # This is mostly arbitrary...the output was generated by running the algo. + edges = [ + (2, 1, 1), + (3, 0, 1), + (3, 4, 1), + (5, 8, 1), + (6, 2, 1), + (7, 3, 1), + (7, 6, 1), + (8, 7, 1), + ] + B_ = build_branching(edges) + assert_equal_branchings(B, B_, default=1) + + +def test_greedy_min(): + G = G1() + B = branchings.greedy_branching(G, kind="min") + + edges = [ + (1, 0, 4), + (0, 2, 12), + (0, 4, 12), + (2, 5, 12), + (4, 7, 12), + (5, 8, 12), + (5, 6, 14), + (7, 3, 19), + ] + B_ = build_branching(edges) + assert_equal_branchings(B, B_) + + +def test_edmonds1_maxbranch(): + G = G1() + x = branchings.maximum_branching(G) + x_ = build_branching(optimal_arborescence_1) + assert_equal_branchings(x, x_) + + +def test_edmonds1_maxarbor(): + G = G1() + x = branchings.maximum_spanning_arborescence(G) + x_ = build_branching(optimal_arborescence_1) + assert_equal_branchings(x, x_) + + +def test_edmonds1_minimal_branching(): + # graph will have something like a minimum arborescence but no spanning one + G = nx.from_numpy_array(G_big_array, create_using=nx.DiGraph) + B = branchings.minimal_branching(G) + edges = [ + (3, 0, 5), + (0, 2, 12), + (0, 4, 12), + (2, 5, 12), + (4, 7, 12), + (5, 8, 12), + (5, 6, 14), + (2, 1, 17), + ] + B_ = build_branching(edges, double=True) + assert_equal_branchings(B, B_) + + +def test_edmonds2_maxbranch(): + G = G2() + x = branchings.maximum_branching(G) + x_ = build_branching(optimal_branching_2a) + assert_equal_branchings(x, x_) + + +def test_edmonds2_maxarbor(): + G = G2() + x = branchings.maximum_spanning_arborescence(G) + x_ = build_branching(optimal_arborescence_2) + assert_equal_branchings(x, x_) + + +def test_edmonds2_minarbor(): + G = G1() + x = branchings.minimum_spanning_arborescence(G) + # This was obtained from algorithm. Need to verify it independently. + # Branch weight is: 96 + edges = [ + (3, 0, 5), + (0, 2, 12), + (0, 4, 12), + (2, 5, 12), + (4, 7, 12), + (5, 8, 12), + (5, 6, 14), + (2, 1, 17), + ] + x_ = build_branching(edges) + assert_equal_branchings(x, x_) + + +def test_edmonds3_minbranch1(): + G = G1() + x = branchings.minimum_branching(G) + edges = [] + x_ = build_branching(edges) + assert_equal_branchings(x, x_) + + +def test_edmonds3_minbranch2(): + G = G1() + G.add_edge(8, 9, weight=-10) + x = branchings.minimum_branching(G) + edges = [(8, 9, -10)] + x_ = build_branching(edges) + assert_equal_branchings(x, x_) + + +# Need more tests + + +def test_mst(): + # Make sure we get the same results for undirected graphs. + # Example from: https://en.wikipedia.org/wiki/Kruskal's_algorithm + G = nx.Graph() + edgelist = [ + (0, 3, [("weight", 5)]), + (0, 1, [("weight", 7)]), + (1, 3, [("weight", 9)]), + (1, 2, [("weight", 8)]), + (1, 4, [("weight", 7)]), + (3, 4, [("weight", 15)]), + (3, 5, [("weight", 6)]), + (2, 4, [("weight", 5)]), + (4, 5, [("weight", 8)]), + (4, 6, [("weight", 9)]), + (5, 6, [("weight", 11)]), + ] + G.add_edges_from(edgelist) + G = G.to_directed() + x = branchings.minimum_spanning_arborescence(G) + + edges = [ + ({0, 1}, 7), + ({0, 3}, 5), + ({3, 5}, 6), + ({1, 4}, 7), + ({4, 2}, 5), + ({4, 6}, 9), + ] + + assert x.number_of_edges() == len(edges) + for u, v, d in x.edges(data=True): + assert ({u, v}, d["weight"]) in edges + + +def test_mixed_nodetypes(): + # Smoke test to make sure no TypeError is raised for mixed node types. + G = nx.Graph() + edgelist = [(0, 3, [("weight", 5)]), (0, "1", [("weight", 5)])] + G.add_edges_from(edgelist) + G = G.to_directed() + x = branchings.minimum_spanning_arborescence(G) + + +def test_edmonds1_minbranch(): + # Using -G_array and min should give the same as optimal_arborescence_1, + # but with all edges negative. + edges = [(u, v, -w) for (u, v, w) in optimal_arborescence_1] + + G = nx.from_numpy_array(-G_array, create_using=nx.DiGraph) + + # Quickly make sure max branching is empty. + x = branchings.maximum_branching(G) + x_ = build_branching([]) + assert_equal_branchings(x, x_) + + # Now test the min branching. + x = branchings.minimum_branching(G) + x_ = build_branching(edges) + assert_equal_branchings(x, x_) + + +def test_edge_attribute_preservation_normal_graph(): + # Test that edge attributes are preserved when finding an optimum graph + # using the Edmonds class for normal graphs. + G = nx.Graph() + + edgelist = [ + (0, 1, [("weight", 5), ("otherattr", 1), ("otherattr2", 3)]), + (0, 2, [("weight", 5), ("otherattr", 2), ("otherattr2", 2)]), + (1, 2, [("weight", 6), ("otherattr", 3), ("otherattr2", 1)]), + ] + G.add_edges_from(edgelist) + + B = branchings.maximum_branching(G, preserve_attrs=True) + + assert B[0][1]["otherattr"] == 1 + assert B[0][1]["otherattr2"] == 3 + + +def test_edge_attribute_preservation_multigraph(): + # Test that edge attributes are preserved when finding an optimum graph + # using the Edmonds class for multigraphs. + G = nx.MultiGraph() + + edgelist = [ + (0, 1, [("weight", 5), ("otherattr", 1), ("otherattr2", 3)]), + (0, 2, [("weight", 5), ("otherattr", 2), ("otherattr2", 2)]), + (1, 2, [("weight", 6), ("otherattr", 3), ("otherattr2", 1)]), + ] + G.add_edges_from(edgelist * 2) # Make sure we have duplicate edge paths + + B = branchings.maximum_branching(G, preserve_attrs=True) + + assert B[0][1][0]["otherattr"] == 1 + assert B[0][1][0]["otherattr2"] == 3 + + +def test_edge_attribute_discard(): + # Test that edge attributes are discarded if we do not specify to keep them + G = nx.Graph() + + edgelist = [ + (0, 1, [("weight", 5), ("otherattr", 1), ("otherattr2", 3)]), + (0, 2, [("weight", 5), ("otherattr", 2), ("otherattr2", 2)]), + (1, 2, [("weight", 6), ("otherattr", 3), ("otherattr2", 1)]), + ] + G.add_edges_from(edgelist) + + B = branchings.maximum_branching(G, preserve_attrs=False) + + edge_dict = B[0][1] + with pytest.raises(KeyError): + _ = edge_dict["otherattr"] + + +def test_partition_spanning_arborescence(): + """ + Test that we can generate minimum spanning arborescences which respect the + given partition. + """ + G = nx.from_numpy_array(G_array, create_using=nx.DiGraph) + G[3][0]["partition"] = nx.EdgePartition.EXCLUDED + G[2][3]["partition"] = nx.EdgePartition.INCLUDED + G[7][3]["partition"] = nx.EdgePartition.EXCLUDED + G[0][2]["partition"] = nx.EdgePartition.EXCLUDED + G[6][2]["partition"] = nx.EdgePartition.INCLUDED + + actual_edges = [ + (0, 4, 12), + (1, 0, 4), + (1, 5, 13), + (2, 3, 21), + (4, 7, 12), + (5, 6, 14), + (5, 8, 12), + (6, 2, 21), + ] + + B = branchings.minimum_spanning_arborescence(G, partition="partition") + assert_equal_branchings(build_branching(actual_edges), B) + + +def test_arborescence_iterator_min(): + """ + Tests the arborescence iterator. + + A brute force method found 680 arborescences in this graph. + This test will not verify all of them individually, but will check two + things + + * The iterator returns 680 arborescences + * The weight of the arborescences is non-strictly increasing + + for more information please visit + https://mjschwenne.github.io/2021/06/10/implementing-the-iterators.html + """ + G = nx.from_numpy_array(G_array, create_using=nx.DiGraph) + + arborescence_count = 0 + arborescence_weight = -math.inf + for B in branchings.ArborescenceIterator(G): + arborescence_count += 1 + new_arborescence_weight = B.size(weight="weight") + assert new_arborescence_weight >= arborescence_weight + arborescence_weight = new_arborescence_weight + + assert arborescence_count == 680 + + +def test_arborescence_iterator_max(): + """ + Tests the arborescence iterator. + + A brute force method found 680 arborescences in this graph. + This test will not verify all of them individually, but will check two + things + + * The iterator returns 680 arborescences + * The weight of the arborescences is non-strictly decreasing + + for more information please visit + https://mjschwenne.github.io/2021/06/10/implementing-the-iterators.html + """ + G = nx.from_numpy_array(G_array, create_using=nx.DiGraph) + + arborescence_count = 0 + arborescence_weight = math.inf + for B in branchings.ArborescenceIterator(G, minimum=False): + arborescence_count += 1 + new_arborescence_weight = B.size(weight="weight") + assert new_arborescence_weight <= arborescence_weight + arborescence_weight = new_arborescence_weight + + assert arborescence_count == 680 + + +def test_arborescence_iterator_initial_partition(): + """ + Tests the arborescence iterator with three included edges and three excluded + in the initial partition. + + A brute force method similar to the one used in the above tests found that + there are 16 arborescences which contain the included edges and not the + excluded edges. + """ + G = nx.from_numpy_array(G_array, create_using=nx.DiGraph) + included_edges = [(1, 0), (5, 6), (8, 7)] + excluded_edges = [(0, 2), (3, 6), (1, 5)] + + arborescence_count = 0 + arborescence_weight = -math.inf + for B in branchings.ArborescenceIterator( + G, init_partition=(included_edges, excluded_edges) + ): + arborescence_count += 1 + new_arborescence_weight = B.size(weight="weight") + assert new_arborescence_weight >= arborescence_weight + arborescence_weight = new_arborescence_weight + for e in included_edges: + assert e in B.edges + for e in excluded_edges: + assert e not in B.edges + assert arborescence_count == 16 + + +def test_branchings_with_default_weights(): + """ + Tests that various branching algorithms work on graphs without weights. + For more information, see issue #7279. + """ + graph = nx.erdos_renyi_graph(10, p=0.2, directed=True, seed=123) + + assert all( + "weight" not in d for (u, v, d) in graph.edges(data=True) + ), "test is for graphs without a weight attribute" + + # Calling these functions will modify graph inplace to add weights + # copy the graph to avoid this. + nx.minimum_spanning_arborescence(graph.copy()) + nx.maximum_spanning_arborescence(graph.copy()) + nx.minimum_branching(graph.copy()) + nx.maximum_branching(graph.copy()) + nx.algorithms.tree.minimal_branching(graph.copy()) + nx.algorithms.tree.branching_weight(graph.copy()) + nx.algorithms.tree.greedy_branching(graph.copy()) + + assert all( + "weight" not in d for (u, v, d) in graph.edges(data=True) + ), "The above calls should not modify the initial graph in-place" diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_coding.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_coding.py new file mode 100644 index 0000000000000000000000000000000000000000..26bd4083f52a0cc90b94c6de6d47b2c44e70a079 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_coding.py @@ -0,0 +1,114 @@ +"""Unit tests for the :mod:`~networkx.algorithms.tree.coding` module.""" + +from itertools import product + +import pytest + +import networkx as nx +from networkx.utils import edges_equal, nodes_equal + + +class TestPruferSequence: + """Unit tests for the Prüfer sequence encoding and decoding + functions. + + """ + + def test_nontree(self): + with pytest.raises(nx.NotATree): + G = nx.cycle_graph(3) + nx.to_prufer_sequence(G) + + def test_null_graph(self): + with pytest.raises(nx.NetworkXPointlessConcept): + nx.to_prufer_sequence(nx.null_graph()) + + def test_trivial_graph(self): + with pytest.raises(nx.NetworkXPointlessConcept): + nx.to_prufer_sequence(nx.trivial_graph()) + + def test_bad_integer_labels(self): + with pytest.raises(KeyError): + T = nx.Graph(nx.utils.pairwise("abc")) + nx.to_prufer_sequence(T) + + def test_encoding(self): + """Tests for encoding a tree as a Prüfer sequence using the + iterative strategy. + + """ + # Example from Wikipedia. + tree = nx.Graph([(0, 3), (1, 3), (2, 3), (3, 4), (4, 5)]) + sequence = nx.to_prufer_sequence(tree) + assert sequence == [3, 3, 3, 4] + + def test_decoding(self): + """Tests for decoding a tree from a Prüfer sequence.""" + # Example from Wikipedia. + sequence = [3, 3, 3, 4] + tree = nx.from_prufer_sequence(sequence) + assert nodes_equal(list(tree), list(range(6))) + edges = [(0, 3), (1, 3), (2, 3), (3, 4), (4, 5)] + assert edges_equal(list(tree.edges()), edges) + + def test_decoding2(self): + # Example from "An Optimal Algorithm for Prufer Codes". + sequence = [2, 4, 0, 1, 3, 3] + tree = nx.from_prufer_sequence(sequence) + assert nodes_equal(list(tree), list(range(8))) + edges = [(0, 1), (0, 4), (1, 3), (2, 4), (2, 5), (3, 6), (3, 7)] + assert edges_equal(list(tree.edges()), edges) + + def test_inverse(self): + """Tests that the encoding and decoding functions are inverses.""" + for T in nx.nonisomorphic_trees(4): + T2 = nx.from_prufer_sequence(nx.to_prufer_sequence(T)) + assert nodes_equal(list(T), list(T2)) + assert edges_equal(list(T.edges()), list(T2.edges())) + + for seq in product(range(4), repeat=2): + seq2 = nx.to_prufer_sequence(nx.from_prufer_sequence(seq)) + assert list(seq) == seq2 + + +class TestNestedTuple: + """Unit tests for the nested tuple encoding and decoding functions.""" + + def test_nontree(self): + with pytest.raises(nx.NotATree): + G = nx.cycle_graph(3) + nx.to_nested_tuple(G, 0) + + def test_unknown_root(self): + with pytest.raises(nx.NodeNotFound): + G = nx.path_graph(2) + nx.to_nested_tuple(G, "bogus") + + def test_encoding(self): + T = nx.full_rary_tree(2, 2**3 - 1) + expected = (((), ()), ((), ())) + actual = nx.to_nested_tuple(T, 0) + assert nodes_equal(expected, actual) + + def test_canonical_form(self): + T = nx.Graph() + T.add_edges_from([(0, 1), (0, 2), (0, 3)]) + T.add_edges_from([(1, 4), (1, 5)]) + T.add_edges_from([(3, 6), (3, 7)]) + root = 0 + actual = nx.to_nested_tuple(T, root, canonical_form=True) + expected = ((), ((), ()), ((), ())) + assert actual == expected + + def test_decoding(self): + balanced = (((), ()), ((), ())) + expected = nx.full_rary_tree(2, 2**3 - 1) + actual = nx.from_nested_tuple(balanced) + assert nx.is_isomorphic(expected, actual) + + def test_sensible_relabeling(self): + balanced = (((), ()), ((), ())) + T = nx.from_nested_tuple(balanced, sensible_relabeling=True) + edges = [(0, 1), (0, 2), (1, 3), (1, 4), (2, 5), (2, 6)] + assert nodes_equal(list(T), list(range(2**3 - 1))) + assert edges_equal(list(T.edges()), edges) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_mst.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_mst.py new file mode 100644 index 0000000000000000000000000000000000000000..f8945a71835dbfa35c0c45259c8c84b653b1f49b --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_mst.py @@ -0,0 +1,918 @@ +"""Unit tests for the :mod:`networkx.algorithms.tree.mst` module.""" + +import pytest + +import networkx as nx +from networkx.utils import edges_equal, nodes_equal + + +def test_unknown_algorithm(): + with pytest.raises(ValueError): + nx.minimum_spanning_tree(nx.Graph(), algorithm="random") + with pytest.raises( + ValueError, match="random is not a valid choice for an algorithm." + ): + nx.maximum_spanning_edges(nx.Graph(), algorithm="random") + + +class MinimumSpanningTreeTestBase: + """Base class for test classes for minimum spanning tree algorithms. + This class contains some common tests that will be inherited by + subclasses. Each subclass must have a class attribute + :data:`algorithm` that is a string representing the algorithm to + run, as described under the ``algorithm`` keyword argument for the + :func:`networkx.minimum_spanning_edges` function. Subclasses can + then implement any algorithm-specific tests. + """ + + def setup_method(self, method): + """Creates an example graph and stores the expected minimum and + maximum spanning tree edges. + """ + # This stores the class attribute `algorithm` in an instance attribute. + self.algo = self.algorithm + # This example graph comes from Wikipedia: + # https://en.wikipedia.org/wiki/Kruskal's_algorithm + edges = [ + (0, 1, 7), + (0, 3, 5), + (1, 2, 8), + (1, 3, 9), + (1, 4, 7), + (2, 4, 5), + (3, 4, 15), + (3, 5, 6), + (4, 5, 8), + (4, 6, 9), + (5, 6, 11), + ] + self.G = nx.Graph() + self.G.add_weighted_edges_from(edges) + self.minimum_spanning_edgelist = [ + (0, 1, {"weight": 7}), + (0, 3, {"weight": 5}), + (1, 4, {"weight": 7}), + (2, 4, {"weight": 5}), + (3, 5, {"weight": 6}), + (4, 6, {"weight": 9}), + ] + self.maximum_spanning_edgelist = [ + (0, 1, {"weight": 7}), + (1, 2, {"weight": 8}), + (1, 3, {"weight": 9}), + (3, 4, {"weight": 15}), + (4, 6, {"weight": 9}), + (5, 6, {"weight": 11}), + ] + + def test_minimum_edges(self): + edges = nx.minimum_spanning_edges(self.G, algorithm=self.algo) + # Edges from the spanning edges functions don't come in sorted + # orientation, so we need to sort each edge individually. + actual = sorted((min(u, v), max(u, v), d) for u, v, d in edges) + assert edges_equal(actual, self.minimum_spanning_edgelist) + + def test_maximum_edges(self): + edges = nx.maximum_spanning_edges(self.G, algorithm=self.algo) + # Edges from the spanning edges functions don't come in sorted + # orientation, so we need to sort each edge individually. + actual = sorted((min(u, v), max(u, v), d) for u, v, d in edges) + assert edges_equal(actual, self.maximum_spanning_edgelist) + + def test_without_data(self): + edges = nx.minimum_spanning_edges(self.G, algorithm=self.algo, data=False) + # Edges from the spanning edges functions don't come in sorted + # orientation, so we need to sort each edge individually. + actual = sorted((min(u, v), max(u, v)) for u, v in edges) + expected = [(u, v) for u, v, d in self.minimum_spanning_edgelist] + assert edges_equal(actual, expected) + + def test_nan_weights(self): + # Edge weights NaN never appear in the spanning tree. see #2164 + G = self.G + G.add_edge(0, 12, weight=float("nan")) + edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, data=False, ignore_nan=True + ) + actual = sorted((min(u, v), max(u, v)) for u, v in edges) + expected = [(u, v) for u, v, d in self.minimum_spanning_edgelist] + assert edges_equal(actual, expected) + # Now test for raising exception + edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, data=False, ignore_nan=False + ) + with pytest.raises(ValueError): + list(edges) + # test default for ignore_nan as False + edges = nx.minimum_spanning_edges(G, algorithm=self.algo, data=False) + with pytest.raises(ValueError): + list(edges) + + def test_nan_weights_MultiGraph(self): + G = nx.MultiGraph() + G.add_edge(0, 12, weight=float("nan")) + edges = nx.minimum_spanning_edges( + G, algorithm="prim", data=False, ignore_nan=False + ) + with pytest.raises(ValueError): + list(edges) + # test default for ignore_nan as False + edges = nx.minimum_spanning_edges(G, algorithm="prim", data=False) + with pytest.raises(ValueError): + list(edges) + + def test_nan_weights_order(self): + # now try again with a nan edge at the beginning of G.nodes + edges = [ + (0, 1, 7), + (0, 3, 5), + (1, 2, 8), + (1, 3, 9), + (1, 4, 7), + (2, 4, 5), + (3, 4, 15), + (3, 5, 6), + (4, 5, 8), + (4, 6, 9), + (5, 6, 11), + ] + G = nx.Graph() + G.add_weighted_edges_from([(u + 1, v + 1, wt) for u, v, wt in edges]) + G.add_edge(0, 7, weight=float("nan")) + edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, data=False, ignore_nan=True + ) + actual = sorted((min(u, v), max(u, v)) for u, v in edges) + shift = [(u + 1, v + 1) for u, v, d in self.minimum_spanning_edgelist] + assert edges_equal(actual, shift) + + def test_isolated_node(self): + # now try again with an isolated node + edges = [ + (0, 1, 7), + (0, 3, 5), + (1, 2, 8), + (1, 3, 9), + (1, 4, 7), + (2, 4, 5), + (3, 4, 15), + (3, 5, 6), + (4, 5, 8), + (4, 6, 9), + (5, 6, 11), + ] + G = nx.Graph() + G.add_weighted_edges_from([(u + 1, v + 1, wt) for u, v, wt in edges]) + G.add_node(0) + edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, data=False, ignore_nan=True + ) + actual = sorted((min(u, v), max(u, v)) for u, v in edges) + shift = [(u + 1, v + 1) for u, v, d in self.minimum_spanning_edgelist] + assert edges_equal(actual, shift) + + def test_minimum_tree(self): + T = nx.minimum_spanning_tree(self.G, algorithm=self.algo) + actual = sorted(T.edges(data=True)) + assert edges_equal(actual, self.minimum_spanning_edgelist) + + def test_maximum_tree(self): + T = nx.maximum_spanning_tree(self.G, algorithm=self.algo) + actual = sorted(T.edges(data=True)) + assert edges_equal(actual, self.maximum_spanning_edgelist) + + def test_disconnected(self): + G = nx.Graph([(0, 1, {"weight": 1}), (2, 3, {"weight": 2})]) + T = nx.minimum_spanning_tree(G, algorithm=self.algo) + assert nodes_equal(list(T), list(range(4))) + assert edges_equal(list(T.edges()), [(0, 1), (2, 3)]) + + def test_empty_graph(self): + G = nx.empty_graph(3) + T = nx.minimum_spanning_tree(G, algorithm=self.algo) + assert nodes_equal(sorted(T), list(range(3))) + assert T.number_of_edges() == 0 + + def test_attributes(self): + G = nx.Graph() + G.add_edge(1, 2, weight=1, color="red", distance=7) + G.add_edge(2, 3, weight=1, color="green", distance=2) + G.add_edge(1, 3, weight=10, color="blue", distance=1) + G.graph["foo"] = "bar" + T = nx.minimum_spanning_tree(G, algorithm=self.algo) + assert T.graph == G.graph + assert nodes_equal(T, G) + for u, v in T.edges(): + assert T.adj[u][v] == G.adj[u][v] + + def test_weight_attribute(self): + G = nx.Graph() + G.add_edge(0, 1, weight=1, distance=7) + G.add_edge(0, 2, weight=30, distance=1) + G.add_edge(1, 2, weight=1, distance=1) + G.add_node(3) + T = nx.minimum_spanning_tree(G, algorithm=self.algo, weight="distance") + assert nodes_equal(sorted(T), list(range(4))) + assert edges_equal(sorted(T.edges()), [(0, 2), (1, 2)]) + T = nx.maximum_spanning_tree(G, algorithm=self.algo, weight="distance") + assert nodes_equal(sorted(T), list(range(4))) + assert edges_equal(sorted(T.edges()), [(0, 1), (0, 2)]) + + +class TestBoruvka(MinimumSpanningTreeTestBase): + """Unit tests for computing a minimum (or maximum) spanning tree + using Borůvka's algorithm. + """ + + algorithm = "boruvka" + + def test_unicode_name(self): + """Tests that using a Unicode string can correctly indicate + Borůvka's algorithm. + """ + edges = nx.minimum_spanning_edges(self.G, algorithm="borůvka") + # Edges from the spanning edges functions don't come in sorted + # orientation, so we need to sort each edge individually. + actual = sorted((min(u, v), max(u, v), d) for u, v, d in edges) + assert edges_equal(actual, self.minimum_spanning_edgelist) + + +class MultigraphMSTTestBase(MinimumSpanningTreeTestBase): + # Abstract class + + def test_multigraph_keys_min(self): + """Tests that the minimum spanning edges of a multigraph + preserves edge keys. + """ + G = nx.MultiGraph() + G.add_edge(0, 1, key="a", weight=2) + G.add_edge(0, 1, key="b", weight=1) + min_edges = nx.minimum_spanning_edges + mst_edges = min_edges(G, algorithm=self.algo, data=False) + assert edges_equal([(0, 1, "b")], list(mst_edges)) + + def test_multigraph_keys_max(self): + """Tests that the maximum spanning edges of a multigraph + preserves edge keys. + """ + G = nx.MultiGraph() + G.add_edge(0, 1, key="a", weight=2) + G.add_edge(0, 1, key="b", weight=1) + max_edges = nx.maximum_spanning_edges + mst_edges = max_edges(G, algorithm=self.algo, data=False) + assert edges_equal([(0, 1, "a")], list(mst_edges)) + + +class TestKruskal(MultigraphMSTTestBase): + """Unit tests for computing a minimum (or maximum) spanning tree + using Kruskal's algorithm. + """ + + algorithm = "kruskal" + + def test_key_data_bool(self): + """Tests that the keys and data values are included in + MST edges based on whether keys and data parameters are + true or false""" + G = nx.MultiGraph() + G.add_edge(1, 2, key=1, weight=2) + G.add_edge(1, 2, key=2, weight=3) + G.add_edge(3, 2, key=1, weight=2) + G.add_edge(3, 1, key=1, weight=4) + + # keys are included and data is not included + mst_edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, keys=True, data=False + ) + assert edges_equal([(1, 2, 1), (2, 3, 1)], list(mst_edges)) + + # keys are not included and data is included + mst_edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, keys=False, data=True + ) + assert edges_equal( + [(1, 2, {"weight": 2}), (2, 3, {"weight": 2})], list(mst_edges) + ) + + # both keys and data are not included + mst_edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, keys=False, data=False + ) + assert edges_equal([(1, 2), (2, 3)], list(mst_edges)) + + # both keys and data are included + mst_edges = nx.minimum_spanning_edges( + G, algorithm=self.algo, keys=True, data=True + ) + assert edges_equal( + [(1, 2, 1, {"weight": 2}), (2, 3, 1, {"weight": 2})], list(mst_edges) + ) + + +class TestPrim(MultigraphMSTTestBase): + """Unit tests for computing a minimum (or maximum) spanning tree + using Prim's algorithm. + """ + + algorithm = "prim" + + def test_prim_mst_edges_simple_graph(self): + H = nx.Graph() + H.add_edge(1, 2, key=2, weight=3) + H.add_edge(3, 2, key=1, weight=2) + H.add_edge(3, 1, key=1, weight=4) + + mst_edges = nx.minimum_spanning_edges(H, algorithm=self.algo, ignore_nan=True) + assert edges_equal( + [(1, 2, {"key": 2, "weight": 3}), (2, 3, {"key": 1, "weight": 2})], + list(mst_edges), + ) + + def test_ignore_nan(self): + """Tests that the edges with NaN weights are ignored or + raise an Error based on ignore_nan is true or false""" + H = nx.MultiGraph() + H.add_edge(1, 2, key=1, weight=float("nan")) + H.add_edge(1, 2, key=2, weight=3) + H.add_edge(3, 2, key=1, weight=2) + H.add_edge(3, 1, key=1, weight=4) + + # NaN weight edges are ignored when ignore_nan=True + mst_edges = nx.minimum_spanning_edges(H, algorithm=self.algo, ignore_nan=True) + assert edges_equal( + [(1, 2, 2, {"weight": 3}), (2, 3, 1, {"weight": 2})], list(mst_edges) + ) + + # NaN weight edges raise Error when ignore_nan=False + with pytest.raises(ValueError): + list(nx.minimum_spanning_edges(H, algorithm=self.algo, ignore_nan=False)) + + def test_multigraph_keys_tree(self): + G = nx.MultiGraph() + G.add_edge(0, 1, key="a", weight=2) + G.add_edge(0, 1, key="b", weight=1) + T = nx.minimum_spanning_tree(G, algorithm=self.algo) + assert edges_equal([(0, 1, 1)], list(T.edges(data="weight"))) + + def test_multigraph_keys_tree_max(self): + G = nx.MultiGraph() + G.add_edge(0, 1, key="a", weight=2) + G.add_edge(0, 1, key="b", weight=1) + T = nx.maximum_spanning_tree(G, algorithm=self.algo) + assert edges_equal([(0, 1, 2)], list(T.edges(data="weight"))) + + +class TestSpanningTreeIterator: + """ + Tests the spanning tree iterator on the example graph in the 2005 Sörensen + and Janssens paper An Algorithm to Generate all Spanning Trees of a Graph in + Order of Increasing Cost + """ + + def setup_method(self): + # Original Graph + edges = [(0, 1, 5), (1, 2, 4), (1, 4, 6), (2, 3, 5), (2, 4, 7), (3, 4, 3)] + self.G = nx.Graph() + self.G.add_weighted_edges_from(edges) + # List of lists of spanning trees in increasing order + self.spanning_trees = [ + # 1, MST, cost = 17 + [ + (0, 1, {"weight": 5}), + (1, 2, {"weight": 4}), + (2, 3, {"weight": 5}), + (3, 4, {"weight": 3}), + ], + # 2, cost = 18 + [ + (0, 1, {"weight": 5}), + (1, 2, {"weight": 4}), + (1, 4, {"weight": 6}), + (3, 4, {"weight": 3}), + ], + # 3, cost = 19 + [ + (0, 1, {"weight": 5}), + (1, 4, {"weight": 6}), + (2, 3, {"weight": 5}), + (3, 4, {"weight": 3}), + ], + # 4, cost = 19 + [ + (0, 1, {"weight": 5}), + (1, 2, {"weight": 4}), + (2, 4, {"weight": 7}), + (3, 4, {"weight": 3}), + ], + # 5, cost = 20 + [ + (0, 1, {"weight": 5}), + (1, 2, {"weight": 4}), + (1, 4, {"weight": 6}), + (2, 3, {"weight": 5}), + ], + # 6, cost = 21 + [ + (0, 1, {"weight": 5}), + (1, 4, {"weight": 6}), + (2, 4, {"weight": 7}), + (3, 4, {"weight": 3}), + ], + # 7, cost = 21 + [ + (0, 1, {"weight": 5}), + (1, 2, {"weight": 4}), + (2, 3, {"weight": 5}), + (2, 4, {"weight": 7}), + ], + # 8, cost = 23 + [ + (0, 1, {"weight": 5}), + (1, 4, {"weight": 6}), + (2, 3, {"weight": 5}), + (2, 4, {"weight": 7}), + ], + ] + + def test_minimum_spanning_tree_iterator(self): + """ + Tests that the spanning trees are correctly returned in increasing order + """ + tree_index = 0 + for tree in nx.SpanningTreeIterator(self.G): + actual = sorted(tree.edges(data=True)) + assert edges_equal(actual, self.spanning_trees[tree_index]) + tree_index += 1 + + def test_maximum_spanning_tree_iterator(self): + """ + Tests that the spanning trees are correctly returned in decreasing order + """ + tree_index = 7 + for tree in nx.SpanningTreeIterator(self.G, minimum=False): + actual = sorted(tree.edges(data=True)) + assert edges_equal(actual, self.spanning_trees[tree_index]) + tree_index -= 1 + + +class TestSpanningTreeMultiGraphIterator: + """ + Uses the same graph as the above class but with an added edge of twice the weight. + """ + + def setup_method(self): + # New graph + edges = [ + (0, 1, 5), + (0, 1, 10), + (1, 2, 4), + (1, 2, 8), + (1, 4, 6), + (1, 4, 12), + (2, 3, 5), + (2, 3, 10), + (2, 4, 7), + (2, 4, 14), + (3, 4, 3), + (3, 4, 6), + ] + self.G = nx.MultiGraph() + self.G.add_weighted_edges_from(edges) + + # There are 128 trees. I'd rather not list all 128 here, and computing them + # on such a small graph actually doesn't take that long. + from itertools import combinations + + self.spanning_trees = [] + for e in combinations(self.G.edges, 4): + tree = self.G.edge_subgraph(e) + if nx.is_tree(tree): + self.spanning_trees.append(sorted(tree.edges(keys=True, data=True))) + + def test_minimum_spanning_tree_iterator_multigraph(self): + """ + Tests that the spanning trees are correctly returned in increasing order + """ + tree_index = 0 + last_weight = 0 + for tree in nx.SpanningTreeIterator(self.G): + actual = sorted(tree.edges(keys=True, data=True)) + weight = sum([e[3]["weight"] for e in actual]) + assert actual in self.spanning_trees + assert weight >= last_weight + tree_index += 1 + + def test_maximum_spanning_tree_iterator_multigraph(self): + """ + Tests that the spanning trees are correctly returned in decreasing order + """ + tree_index = 127 + # Maximum weight tree is 46 + last_weight = 50 + for tree in nx.SpanningTreeIterator(self.G, minimum=False): + actual = sorted(tree.edges(keys=True, data=True)) + weight = sum([e[3]["weight"] for e in actual]) + assert actual in self.spanning_trees + assert weight <= last_weight + tree_index -= 1 + + +def test_random_spanning_tree_multiplicative_small(): + """ + Using a fixed seed, sample one tree for repeatability. + """ + from math import exp + + pytest.importorskip("scipy") + + gamma = { + (0, 1): -0.6383, + (0, 2): -0.6827, + (0, 5): 0, + (1, 2): -1.0781, + (1, 4): 0, + (2, 3): 0, + (5, 3): -0.2820, + (5, 4): -0.3327, + (4, 3): -0.9927, + } + + # The undirected support of gamma + G = nx.Graph() + for u, v in gamma: + G.add_edge(u, v, lambda_key=exp(gamma[(u, v)])) + + solution_edges = [(2, 3), (3, 4), (0, 5), (5, 4), (4, 1)] + solution = nx.Graph() + solution.add_edges_from(solution_edges) + + sampled_tree = nx.random_spanning_tree(G, "lambda_key", seed=42) + + assert nx.utils.edges_equal(solution.edges, sampled_tree.edges) + + +@pytest.mark.slow +def test_random_spanning_tree_multiplicative_large(): + """ + Sample many trees from the distribution created in the last test + """ + from math import exp + from random import Random + + pytest.importorskip("numpy") + stats = pytest.importorskip("scipy.stats") + + gamma = { + (0, 1): -0.6383, + (0, 2): -0.6827, + (0, 5): 0, + (1, 2): -1.0781, + (1, 4): 0, + (2, 3): 0, + (5, 3): -0.2820, + (5, 4): -0.3327, + (4, 3): -0.9927, + } + + # The undirected support of gamma + G = nx.Graph() + for u, v in gamma: + G.add_edge(u, v, lambda_key=exp(gamma[(u, v)])) + + # Find the multiplicative weight for each tree. + total_weight = 0 + tree_expected = {} + for t in nx.SpanningTreeIterator(G): + # Find the multiplicative weight of the spanning tree + weight = 1 + for u, v, d in t.edges(data="lambda_key"): + weight *= d + tree_expected[t] = weight + total_weight += weight + + # Assert that every tree has an entry in the expected distribution + assert len(tree_expected) == 75 + + # Set the sample size and then calculate the expected number of times we + # expect to see each tree. This test uses a near minimum sample size where + # the most unlikely tree has an expected frequency of 5.15. + # (Minimum required is 5) + # + # Here we also initialize the tree_actual dict so that we know the keys + # match between the two. We will later take advantage of the fact that since + # python 3.7 dict order is guaranteed so the expected and actual data will + # have the same order. + sample_size = 1200 + tree_actual = {} + for t in tree_expected: + tree_expected[t] = (tree_expected[t] / total_weight) * sample_size + tree_actual[t] = 0 + + # Sample the spanning trees + # + # Assert that they are actually trees and record which of the 75 trees we + # have sampled. + # + # For repeatability, we want to take advantage of the decorators in NetworkX + # to randomly sample the same sample each time. However, if we pass in a + # constant seed to sample_spanning_tree we will get the same tree each time. + # Instead, we can create our own random number generator with a fixed seed + # and pass those into sample_spanning_tree. + rng = Random(37) + for _ in range(sample_size): + sampled_tree = nx.random_spanning_tree(G, "lambda_key", seed=rng) + assert nx.is_tree(sampled_tree) + + for t in tree_expected: + if nx.utils.edges_equal(t.edges, sampled_tree.edges): + tree_actual[t] += 1 + break + + # Conduct a Chi squared test to see if the actual distribution matches the + # expected one at an alpha = 0.05 significance level. + # + # H_0: The distribution of trees in tree_actual matches the normalized product + # of the edge weights in the tree. + # + # H_a: The distribution of trees in tree_actual follows some other + # distribution of spanning trees. + _, p = stats.chisquare(list(tree_actual.values()), list(tree_expected.values())) + + # Assert that p is greater than the significance level so that we do not + # reject the null hypothesis + assert not p < 0.05 + + +def test_random_spanning_tree_additive_small(): + """ + Sample a single spanning tree from the additive method. + """ + pytest.importorskip("scipy") + + edges = { + (0, 1): 1, + (0, 2): 1, + (0, 5): 3, + (1, 2): 2, + (1, 4): 3, + (2, 3): 3, + (5, 3): 4, + (5, 4): 5, + (4, 3): 4, + } + + # Build the graph + G = nx.Graph() + for u, v in edges: + G.add_edge(u, v, weight=edges[(u, v)]) + + solution_edges = [(0, 2), (1, 2), (2, 3), (3, 4), (3, 5)] + solution = nx.Graph() + solution.add_edges_from(solution_edges) + + sampled_tree = nx.random_spanning_tree( + G, weight="weight", multiplicative=False, seed=37 + ) + + assert nx.utils.edges_equal(solution.edges, sampled_tree.edges) + + +@pytest.mark.slow +def test_random_spanning_tree_additive_large(): + """ + Sample many spanning trees from the additive method. + """ + from random import Random + + pytest.importorskip("numpy") + stats = pytest.importorskip("scipy.stats") + + edges = { + (0, 1): 1, + (0, 2): 1, + (0, 5): 3, + (1, 2): 2, + (1, 4): 3, + (2, 3): 3, + (5, 3): 4, + (5, 4): 5, + (4, 3): 4, + } + + # Build the graph + G = nx.Graph() + for u, v in edges: + G.add_edge(u, v, weight=edges[(u, v)]) + + # Find the additive weight for each tree. + total_weight = 0 + tree_expected = {} + for t in nx.SpanningTreeIterator(G): + # Find the multiplicative weight of the spanning tree + weight = 0 + for u, v, d in t.edges(data="weight"): + weight += d + tree_expected[t] = weight + total_weight += weight + + # Assert that every tree has an entry in the expected distribution + assert len(tree_expected) == 75 + + # Set the sample size and then calculate the expected number of times we + # expect to see each tree. This test uses a near minimum sample size where + # the most unlikely tree has an expected frequency of 5.07. + # (Minimum required is 5) + # + # Here we also initialize the tree_actual dict so that we know the keys + # match between the two. We will later take advantage of the fact that since + # python 3.7 dict order is guaranteed so the expected and actual data will + # have the same order. + sample_size = 500 + tree_actual = {} + for t in tree_expected: + tree_expected[t] = (tree_expected[t] / total_weight) * sample_size + tree_actual[t] = 0 + + # Sample the spanning trees + # + # Assert that they are actually trees and record which of the 75 trees we + # have sampled. + # + # For repeatability, we want to take advantage of the decorators in NetworkX + # to randomly sample the same sample each time. However, if we pass in a + # constant seed to sample_spanning_tree we will get the same tree each time. + # Instead, we can create our own random number generator with a fixed seed + # and pass those into sample_spanning_tree. + rng = Random(37) + for _ in range(sample_size): + sampled_tree = nx.random_spanning_tree( + G, "weight", multiplicative=False, seed=rng + ) + assert nx.is_tree(sampled_tree) + + for t in tree_expected: + if nx.utils.edges_equal(t.edges, sampled_tree.edges): + tree_actual[t] += 1 + break + + # Conduct a Chi squared test to see if the actual distribution matches the + # expected one at an alpha = 0.05 significance level. + # + # H_0: The distribution of trees in tree_actual matches the normalized product + # of the edge weights in the tree. + # + # H_a: The distribution of trees in tree_actual follows some other + # distribution of spanning trees. + _, p = stats.chisquare(list(tree_actual.values()), list(tree_expected.values())) + + # Assert that p is greater than the significance level so that we do not + # reject the null hypothesis + assert not p < 0.05 + + +def test_random_spanning_tree_empty_graph(): + G = nx.Graph() + rst = nx.tree.random_spanning_tree(G) + assert len(rst.nodes) == 0 + assert len(rst.edges) == 0 + + +def test_random_spanning_tree_single_node_graph(): + G = nx.Graph() + G.add_node(0) + rst = nx.tree.random_spanning_tree(G) + assert len(rst.nodes) == 1 + assert len(rst.edges) == 0 + + +def test_random_spanning_tree_single_node_loop(): + G = nx.Graph() + G.add_node(0) + G.add_edge(0, 0) + rst = nx.tree.random_spanning_tree(G) + assert len(rst.nodes) == 1 + assert len(rst.edges) == 0 + + +class TestNumberSpanningTrees: + @classmethod + def setup_class(cls): + global np + np = pytest.importorskip("numpy") + sp = pytest.importorskip("scipy") + + def test_nst_disconnected(self): + G = nx.empty_graph(2) + assert np.isclose(nx.number_of_spanning_trees(G), 0) + + def test_nst_no_nodes(self): + G = nx.Graph() + with pytest.raises(nx.NetworkXPointlessConcept): + nx.number_of_spanning_trees(G) + + def test_nst_weight(self): + G = nx.Graph() + G.add_edge(1, 2, weight=1) + G.add_edge(1, 3, weight=1) + G.add_edge(2, 3, weight=2) + # weights are ignored + assert np.isclose(nx.number_of_spanning_trees(G), 3) + # including weight + assert np.isclose(nx.number_of_spanning_trees(G, weight="weight"), 5) + + def test_nst_negative_weight(self): + G = nx.Graph() + G.add_edge(1, 2, weight=1) + G.add_edge(1, 3, weight=-1) + G.add_edge(2, 3, weight=-2) + # weights are ignored + assert np.isclose(nx.number_of_spanning_trees(G), 3) + # including weight + assert np.isclose(nx.number_of_spanning_trees(G, weight="weight"), -1) + + def test_nst_selfloop(self): + # self-loops are ignored + G = nx.complete_graph(3) + G.add_edge(1, 1) + assert np.isclose(nx.number_of_spanning_trees(G), 3) + + def test_nst_multigraph(self): + G = nx.MultiGraph() + G.add_edge(1, 2) + G.add_edge(1, 2) + G.add_edge(1, 3) + G.add_edge(2, 3) + assert np.isclose(nx.number_of_spanning_trees(G), 5) + + def test_nst_complete_graph(self): + # this is known as Cayley's formula + N = 5 + G = nx.complete_graph(N) + assert np.isclose(nx.number_of_spanning_trees(G), N ** (N - 2)) + + def test_nst_path_graph(self): + G = nx.path_graph(5) + assert np.isclose(nx.number_of_spanning_trees(G), 1) + + def test_nst_cycle_graph(self): + G = nx.cycle_graph(5) + assert np.isclose(nx.number_of_spanning_trees(G), 5) + + def test_nst_directed_noroot(self): + G = nx.empty_graph(3, create_using=nx.MultiDiGraph) + with pytest.raises(nx.NetworkXError): + nx.number_of_spanning_trees(G) + + def test_nst_directed_root_not_exist(self): + G = nx.empty_graph(3, create_using=nx.MultiDiGraph) + with pytest.raises(nx.NetworkXError): + nx.number_of_spanning_trees(G, root=42) + + def test_nst_directed_not_weak_connected(self): + G = nx.DiGraph() + G.add_edge(1, 2) + G.add_edge(3, 4) + assert np.isclose(nx.number_of_spanning_trees(G, root=1), 0) + + def test_nst_directed_cycle_graph(self): + G = nx.DiGraph() + G = nx.cycle_graph(7, G) + assert np.isclose(nx.number_of_spanning_trees(G, root=0), 1) + + def test_nst_directed_complete_graph(self): + G = nx.DiGraph() + G = nx.complete_graph(7, G) + assert np.isclose(nx.number_of_spanning_trees(G, root=0), 7**5) + + def test_nst_directed_multi(self): + G = nx.MultiDiGraph() + G = nx.cycle_graph(3, G) + G.add_edge(1, 2) + assert np.isclose(nx.number_of_spanning_trees(G, root=0), 2) + + def test_nst_directed_selfloop(self): + G = nx.MultiDiGraph() + G = nx.cycle_graph(3, G) + G.add_edge(1, 1) + assert np.isclose(nx.number_of_spanning_trees(G, root=0), 1) + + def test_nst_directed_weak_connected(self): + G = nx.MultiDiGraph() + G = nx.cycle_graph(3, G) + G.remove_edge(1, 2) + assert np.isclose(nx.number_of_spanning_trees(G, root=0), 0) + + def test_nst_directed_weighted(self): + # from root=1: + # arborescence 1: 1->2, 1->3, weight=2*1 + # arborescence 2: 1->2, 2->3, weight=2*3 + G = nx.DiGraph() + G.add_edge(1, 2, weight=2) + G.add_edge(1, 3, weight=1) + G.add_edge(2, 3, weight=3) + Nst = nx.number_of_spanning_trees(G, root=1, weight="weight") + assert np.isclose(Nst, 8) + Nst = nx.number_of_spanning_trees(G, root=2, weight="weight") + assert np.isclose(Nst, 0) + Nst = nx.number_of_spanning_trees(G, root=3, weight="weight") + assert np.isclose(Nst, 0) diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_operations.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_operations.py new file mode 100644 index 0000000000000000000000000000000000000000..284d94e2e5059de267b5ea47f6012a42c6ac4639 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_operations.py @@ -0,0 +1,53 @@ +from itertools import chain + +import networkx as nx +from networkx.utils import edges_equal, nodes_equal + + +def _check_custom_label_attribute(input_trees, res_tree, label_attribute): + res_attr_dict = nx.get_node_attributes(res_tree, label_attribute) + res_attr_set = set(res_attr_dict.values()) + input_label = (tree for tree, root in input_trees) + input_label_set = set(chain.from_iterable(input_label)) + return res_attr_set == input_label_set + + +def test_empty_sequence(): + """Joining the empty sequence results in the tree with one node.""" + T = nx.join_trees([]) + assert len(T) == 1 + assert T.number_of_edges() == 0 + + +def test_single(): + """Joining just one tree yields a tree with one more node.""" + T = nx.empty_graph(1) + trees = [(T, 0)] + actual_with_label = nx.join_trees(trees, label_attribute="custom_label") + expected = nx.path_graph(2) + assert nodes_equal(list(expected), list(actual_with_label)) + assert edges_equal(list(expected.edges()), list(actual_with_label.edges())) + + +def test_basic(): + """Joining multiple subtrees at a root node.""" + trees = [(nx.full_rary_tree(2, 2**2 - 1), 0) for i in range(2)] + expected = nx.full_rary_tree(2, 2**3 - 1) + actual = nx.join_trees(trees, label_attribute="old_labels") + assert nx.is_isomorphic(actual, expected) + assert _check_custom_label_attribute(trees, actual, "old_labels") + + actual_without_label = nx.join_trees(trees) + assert nx.is_isomorphic(actual_without_label, expected) + # check that no labels were stored + assert all(not data for _, data in actual_without_label.nodes(data=True)) + + +def test_first_label(): + """Test the functionality of the first_label argument.""" + T1 = nx.path_graph(3) + T2 = nx.path_graph(2) + actual = nx.join_trees([(T1, 0), (T2, 0)], first_label=10) + expected_nodes = set(range(10, 16)) + assert set(actual.nodes()) == expected_nodes + assert set(actual.neighbors(10)) == {11, 14} diff --git a/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_recognition.py b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_recognition.py new file mode 100644 index 0000000000000000000000000000000000000000..105f5a89e9b10d37d1cc140880a66bc860d2e9f8 --- /dev/null +++ b/janus/lib/python3.10/site-packages/networkx/algorithms/tree/tests/test_recognition.py @@ -0,0 +1,174 @@ +import pytest + +import networkx as nx + + +class TestTreeRecognition: + graph = nx.Graph + multigraph = nx.MultiGraph + + @classmethod + def setup_class(cls): + cls.T1 = cls.graph() + + cls.T2 = cls.graph() + cls.T2.add_node(1) + + cls.T3 = cls.graph() + cls.T3.add_nodes_from(range(5)) + edges = [(i, i + 1) for i in range(4)] + cls.T3.add_edges_from(edges) + + cls.T5 = cls.multigraph() + cls.T5.add_nodes_from(range(5)) + edges = [(i, i + 1) for i in range(4)] + cls.T5.add_edges_from(edges) + + cls.T6 = cls.graph() + cls.T6.add_nodes_from([6, 7]) + cls.T6.add_edge(6, 7) + + cls.F1 = nx.compose(cls.T6, cls.T3) + + cls.N4 = cls.graph() + cls.N4.add_node(1) + cls.N4.add_edge(1, 1) + + cls.N5 = cls.graph() + cls.N5.add_nodes_from(range(5)) + + cls.N6 = cls.graph() + cls.N6.add_nodes_from(range(3)) + cls.N6.add_edges_from([(0, 1), (1, 2), (2, 0)]) + + cls.NF1 = nx.compose(cls.T6, cls.N6) + + def test_null_tree(self): + with pytest.raises(nx.NetworkXPointlessConcept): + nx.is_tree(self.graph()) + + def test_null_tree2(self): + with pytest.raises(nx.NetworkXPointlessConcept): + nx.is_tree(self.multigraph()) + + def test_null_forest(self): + with pytest.raises(nx.NetworkXPointlessConcept): + nx.is_forest(self.graph()) + + def test_null_forest2(self): + with pytest.raises(nx.NetworkXPointlessConcept): + nx.is_forest(self.multigraph()) + + def test_is_tree(self): + assert nx.is_tree(self.T2) + assert nx.is_tree(self.T3) + assert nx.is_tree(self.T5) + + def test_is_not_tree(self): + assert not nx.is_tree(self.N4) + assert not nx.is_tree(self.N5) + assert not nx.is_tree(self.N6) + + def test_is_forest(self): + assert nx.is_forest(self.T2) + assert nx.is_forest(self.T3) + assert nx.is_forest(self.T5) + assert nx.is_forest(self.F1) + assert nx.is_forest(self.N5) + + def test_is_not_forest(self): + assert not nx.is_forest(self.N4) + assert not nx.is_forest(self.N6) + assert not nx.is_forest(self.NF1) + + +class TestDirectedTreeRecognition(TestTreeRecognition): + graph = nx.DiGraph + multigraph = nx.MultiDiGraph + + +def test_disconnected_graph(): + # https://github.com/networkx/networkx/issues/1144 + G = nx.Graph() + G.add_edges_from([(0, 1), (1, 2), (2, 0), (3, 4)]) + assert not nx.is_tree(G) + + G = nx.DiGraph() + G.add_edges_from([(0, 1), (1, 2), (2, 0), (3, 4)]) + assert not nx.is_tree(G) + + +def test_dag_nontree(): + G = nx.DiGraph() + G.add_edges_from([(0, 1), (0, 2), (1, 2)]) + assert not nx.is_tree(G) + assert nx.is_directed_acyclic_graph(G) + + +def test_multicycle(): + G = nx.MultiDiGraph() + G.add_edges_from([(0, 1), (0, 1)]) + assert not nx.is_tree(G) + assert nx.is_directed_acyclic_graph(G) + + +def test_emptybranch(): + G = nx.DiGraph() + G.add_nodes_from(range(10)) + assert nx.is_branching(G) + assert not nx.is_arborescence(G) + + +def test_is_branching_empty_graph_raises(): + G = nx.DiGraph() + with pytest.raises(nx.NetworkXPointlessConcept, match="G has no nodes."): + nx.is_branching(G) + + +def test_path(): + G = nx.DiGraph() + nx.add_path(G, range(5)) + assert nx.is_branching(G) + assert nx.is_arborescence(G) + + +def test_notbranching1(): + # Acyclic violation. + G = nx.MultiDiGraph() + G.add_nodes_from(range(10)) + G.add_edges_from([(0, 1), (1, 0)]) + assert not nx.is_branching(G) + assert not nx.is_arborescence(G) + + +def test_notbranching2(): + # In-degree violation. + G = nx.MultiDiGraph() + G.add_nodes_from(range(10)) + G.add_edges_from([(0, 1), (0, 2), (3, 2)]) + assert not nx.is_branching(G) + assert not nx.is_arborescence(G) + + +def test_notarborescence1(): + # Not an arborescence due to not spanning. + G = nx.MultiDiGraph() + G.add_nodes_from(range(10)) + G.add_edges_from([(0, 1), (0, 2), (1, 3), (5, 6)]) + assert nx.is_branching(G) + assert not nx.is_arborescence(G) + + +def test_notarborescence2(): + # Not an arborescence due to in-degree violation. + G = nx.MultiDiGraph() + nx.add_path(G, range(5)) + G.add_edge(6, 4) + assert not nx.is_branching(G) + assert not nx.is_arborescence(G) + + +def test_is_arborescense_empty_graph_raises(): + G = nx.DiGraph() + with pytest.raises(nx.NetworkXPointlessConcept, match="G has no nodes."): + nx.is_arborescence(G)