paper_extraction / src /extract_cross_barcode_features.py
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"""Cross-barcode (PairedAttention) features via Prim-MST RTD approximation.
Port of `RTD_simplified_summ_only` from paper/drive_folder/cross_barcodes_approximation.ipynb,
generalized over the 144 (layer, head) pairs and across samples, with a batched GPU
implementation that processes all pairs of a sample in parallel.
Public API:
- ``rtd_simplified(a1, a2, q)`` β€” single-pair convenience wrapper.
- ``rtd_simplified_batched(A1, A2, q)`` β€” vectorized over P pairs at once.
- ``compute_cross_barcode_features(...)`` β€” runs the pipeline over a dataset.
Private:
- ``_prim_mst_sum_loop(adj)`` β€” original per-matrix reference (slow, single).
- ``_prim_mst_sum(adj)`` β€” batched implementation; accepts (n,n) or (B,n,n).
- ``_rtd_simplified_loop(a1,a2,q)`` β€” original notebook-faithful single-pair reference.
"""
from __future__ import annotations
from pathlib import Path
from typing import List, Tuple
import numpy as np
import torch
from tqdm import tqdm
# ---------------------------------------------------------------------------
# Reference implementations (kept for tests)
# ---------------------------------------------------------------------------
def _prim_mst_sum_loop(adj: torch.Tensor) -> torch.Tensor:
"""Reference single-matrix Prim-MST sum (loop form).
Faithful re-implementation of paper/drive_folder/cross_barcodes_approximation.ipynb
`prim_algo_simplified`.
"""
n = adj.shape[0]
infty = adj.max().item() + 10.0
dst = torch.full((n,), infty, device=adj.device, dtype=adj.dtype)
anc = -torch.ones(n, device=adj.device, dtype=torch.long)
visited = torch.zeros(n, device=adj.device, dtype=torch.bool)
s = torch.zeros((), device=adj.device, dtype=adj.dtype)
v = 0
for _ in range(n - 1):
visited[v] = True
improved = dst > adj[v]
anc = torch.where(improved, torch.full_like(anc, v), anc)
dst = torch.minimum(dst, adj[v])
dst = torch.where(visited, torch.full_like(dst, infty), dst)
v = int(torch.argmin(dst).item())
s = s + adj[v, anc[v]]
return s
def _rtd_simplified_loop(a1: torch.Tensor, a2: torch.Tensor, q: float = 0.9) -> torch.Tensor:
"""Reference single-pair RTD (loop form)."""
r1 = a1 / torch.quantile(a1, q)
r2 = a2 / torch.quantile(a2, q)
rmin = torch.minimum(r1, r2)
return (_prim_mst_sum_loop(r1) - _prim_mst_sum_loop(rmin)) + (
_prim_mst_sum_loop(r2) - _prim_mst_sum_loop(rmin)
)
# ---------------------------------------------------------------------------
# Batched implementation (production path)
# ---------------------------------------------------------------------------
def _prim_mst_sum(adj: torch.Tensor) -> torch.Tensor:
"""Sum of MST edge weights for a batch of dense weighted adjacency matrices.
Accepts either (n, n) or (B, n, n). Equivalent to running Prim's algorithm
independently on each matrix in the batch, but with the inner ``argmin``
loop running once across the whole batch in a single GPU kernel per step.
Returns:
() if input was (n, n); (B,) if input was (B, n, n).
"""
squeeze_out = False
if adj.ndim == 2:
adj = adj.unsqueeze(0)
squeeze_out = True
B, n, _ = adj.shape
device, dtype = adj.device, adj.dtype
infty = float(adj.amax().item() + 10.0)
dst = torch.full((B, n), infty, device=device, dtype=dtype)
anc = torch.full((B, n), -1, device=device, dtype=torch.long)
visited = torch.zeros((B, n), device=device, dtype=torch.bool)
s = torch.zeros(B, device=device, dtype=dtype)
v = torch.zeros(B, device=device, dtype=torch.long) # all start at vertex 0
batch_idx = torch.arange(B, device=device)
for _ in range(n - 1):
visited[batch_idx, v] = True
row = adj[batch_idx, v] # (B, n)
improved = dst > row # (B, n)
anc = torch.where(improved, v.unsqueeze(1).expand_as(anc), anc)
dst = torch.minimum(dst, row)
dst = torch.where(visited, torch.full_like(dst, infty), dst)
v = dst.argmin(dim=1) # (B,)
s = s + adj[batch_idx, v, anc[batch_idx, v]]
return s.squeeze(0) if squeeze_out else s
def rtd_simplified_batched(a1: torch.Tensor, a2: torch.Tensor, q: float = 0.9) -> torch.Tensor:
"""Batched sum-of-MST RTD estimator.
Args:
a1, a2: shape (P, n, n) β€” P pairs of nΓ—n attention matrices.
Returns:
rtd: shape (P,) RTD scores.
"""
P = a1.shape[0]
a1_flat = a1.reshape(P, -1)
a2_flat = a2.reshape(P, -1)
q1 = torch.quantile(a1_flat, q, dim=1).view(P, 1, 1)
q2 = torch.quantile(a2_flat, q, dim=1).view(P, 1, 1)
r1 = a1 / q1
r2 = a2 / q2
rmin = torch.minimum(r1, r2)
stacked = torch.cat([r1, r2, rmin], dim=0) # (3P, n, n)
s = _prim_mst_sum(stacked).view(3, P)
r1_sum, r2_sum, rmin_sum = s[0], s[1], s[2]
return (r1_sum - rmin_sum) + (r2_sum - rmin_sum)
def rtd_simplified(a1: torch.Tensor, a2: torch.Tensor, q: float = 0.9) -> torch.Tensor:
"""Single-pair RTD β€” thin wrapper over the batched path."""
return rtd_simplified_batched(a1.unsqueeze(0), a2.unsqueeze(0), q=q).squeeze(0)
# ---------------------------------------------------------------------------
# Pair selection strategies
# ---------------------------------------------------------------------------
def _pairs_all_144() -> List[Tuple[int, int, int, int]]:
"""144 pairs: last-layer heads (11, j) crossed with last-head layers (k, 11)."""
pairs = []
for j in range(12):
for k in range(12):
pairs.append((11, j, k, 11))
return pairs
def _pairs_last_layer() -> List[Tuple[int, int, int, int]]:
"""Cross-barcodes **inside the last layer** β€” every unordered pair of heads
(hi, hj) within layer 11, excluding the diagonal hi == hj (RTD is symmetric
and zero on identical matrices). 12 choose 2 = 66 pairs.
"""
return _pairs_last_n_layers(1)
def _pairs_last_n_layers(n: int) -> List[Tuple[int, int, int, int]]:
"""All unique unordered pairs among the (layer, head) attention matrices
drawn from the last ``n`` layers β€” that is, layers in [12 - n, 11].
With L=12 layers and H=12 heads, this yields ``C(n*H, 2)`` pairs:
n=1 β†’ 66, n=2 β†’ 276, n=3 β†’ 630, n=4 β†’ 1128, n=12 β†’ 10296.
"""
L, H = 12, 12
layers = list(range(L - n, L))
attentions = [(layer, head) for layer in layers for head in range(H)]
out = []
for i in range(len(attentions)):
for j in range(i + 1, len(attentions)):
li, hi = attentions[i]
lj, hj = attentions[j]
out.append((li, hi, lj, hj))
return out
def _pairs_stratified(layer_indices: List[int]) -> List[Tuple[int, int, int, int]]:
"""All unordered (layer, head) pairs among heads at the given layer indices.
With H=12 heads per layer, len(layer_indices)=k gives C(k*H, 2) pairs.
k=3 β†’ 630, k=4 β†’ 1128.
"""
H = 12
attentions = [(layer, head) for layer in layer_indices for head in range(H)]
out = []
for i in range(len(attentions)):
for j in range(i + 1, len(attentions)):
li, hi = attentions[i]
lj, hj = attentions[j]
out.append((li, hi, lj, hj))
return out
def _resolve_pairs(strategy: str) -> List[Tuple[int, int, int, int]]:
if strategy == "all_144":
return _pairs_all_144()
if strategy == "last_layer":
return _pairs_last_n_layers(1)
if strategy == "last_2_layers":
return _pairs_last_n_layers(2)
if strategy == "last_3_layers":
return _pairs_last_n_layers(3)
if strategy == "last_4_layers":
return _pairs_last_n_layers(4)
if strategy == "all_pairs":
return _pairs_last_n_layers(12) # all C(144, 2) = 10,296 pairs
# Stratified depth-spanning strategies (start / middle / end)
if strategy == "stratified_3":
return _pairs_stratified([1, 6, 11]) # early / mid / late, 36 heads β†’ 630 pairs
if strategy == "stratified_4":
return _pairs_stratified([0, 4, 8, 11]) # 48 heads β†’ 1128 pairs
if strategy == "stratified_6":
return _pairs_stratified([0, 2, 5, 7, 9, 11]) # 72 heads β†’ 2556 pairs
# Paper's i–k–j strategy (Kostenok et al. Β§III.A): for fixed pivot layer k,
# pair (A_{i,k}, A_{k,j}) β€” i.e. heads at layer-i ↔ heads at layer-j with
# head index = k or j respectively. We interpret this as "fix pivot
# layer k, pair layer-i head k vs layer-j head h_pivot for every (i, j) in
# the layer grid". The paper's tensor shape (12,12,144) suggests
# 12 Γ— 12 = 144 unique (i, j) ordered pairs per pivot k.
if strategy == "paper_ikj_k11":
return _pairs_paper_ikj(k_layers=[11]) # 144 ordered pairs β†’ 78 unordered
if strategy == "paper_ikj_k6":
return _pairs_paper_ikj(k_layers=[6])
if strategy == "paper_ikj_multi":
return _pairs_paper_ikj(k_layers=[3, 6, 9, 11]) # 4 pivots β†’ ~300 unique pairs
raise ValueError(f"unknown pairs_strategy: {strategy}")
def _pairs_paper_ikj(k_layers: List[int]) -> List[Tuple[int, int, int, int]]:
"""Paper's i-k-j cross-barcode pairing: for each pivot layer k and each
layer pair (i, j), generate (layer_i head_k, layer_j head_k).
All 12 Γ— 12 ordered (i, j) for a fixed k β†’ 144 directed pairs. We keep
only unordered (i < j) for symmetry β†’ 78 per pivot. Multi-pivot stacks.
"""
L = 12
seen = set()
out = []
for k in k_layers:
for i in range(L):
for j in range(L):
if i == j:
continue
# treat k as the shared head index for both matrices
a, b = (i, k), (j, k)
if (a, b) in seen or (b, a) in seen:
continue
seen.add((a, b))
out.append((i, k, j, k))
return out
# ---------------------------------------------------------------------------
# Driver
# ---------------------------------------------------------------------------
def compute_cross_barcode_features(
attn_dir: Path,
indices: List[int],
*,
device: torch.device,
pairs_strategy: str = "last_layer",
quantile: float = 0.9,
) -> Tuple[np.ndarray, List[str]]:
pairs = _resolve_pairs(pairs_strategy)
feature_names = [f"cb_L{li}H{hi}_L{lj}H{hj}" for li, hi, lj, hj in pairs]
P = len(pairs)
pairs_t = torch.tensor(pairs, device=device, dtype=torch.long)
li, hi, lj, hj = pairs_t[:, 0], pairs_t[:, 1], pairs_t[:, 2], pairs_t[:, 3]
out = np.zeros((len(indices), P), dtype=np.float32)
for n, idx in enumerate(tqdm(indices, desc="cross-barcode")):
path = attn_dir / f"{idx:06d}.npz"
with np.load(path) as data:
attn = data["attn"].astype(np.float32) # (L, H, T, T)
attn_t = torch.from_numpy(attn).to(device)
A1 = attn_t[li, hi] # (P, T, T)
A2 = attn_t[lj, hj] # (P, T, T)
out[n] = rtd_simplified_batched(A1, A2, q=quantile).detach().cpu().numpy()
return out, feature_names