add PermutationResetSampler

automata.py

@@ -699,7 +699,55 @@ class QuaternionSampler(AutomatonSampler):
     return x, self.f(x)
 
 
+class PermutationResetSampler(AutomatonSampler):
+  def __init__(self, data_config):
+    super().__init__(data_config)
+
+    self.n = data_config['n']
+    self.generators = data_config['generators']
+    self.perm_probs = data_config['perm_probs']
+    if type(self.generators[0]) is str:
+        self.generators = [ np.array(list(map(int, list(g)))) for g in self.generators ]
+
+    self.vocab_size = math.factorial(self.n) # states = permutations; maybe rename
+    self.n_generators = len(self.generators) # actions = generators
+    self.n_actions = self.vocab_size + self.n_generators # 1 reset symbol per state, 1 apply symbol per generator
 
+    self.init_state = np.arange(self.n) # identity permutation
+    
+    # lookup tables
+    self.int2perm = list(map(np.array, itertools.permutations(range(self.n))))
+    self.perm2int = {tuple(p):i for i,p in enumerate(self.int2perm)}
+    
+    # interval lengths
+    T = self.sample_length()
+    self.lags = [1]
+    while self.lags[-1]*2 < T:
+        self.lags.append(self.lags[-1]*2)
+
+  def f(self, x):
+    curr_state = self.init_state
+    states = []
+    for action_id in x:
+      if action_id >= self.vocab_size:
+        curr_state = self.generators[action_id - self.vocab_size][curr_state]
+      else:
+        curr_state = self.int2perm[action_id]
+      states.append(self.perm2int[tuple(curr_state)])
+    return np.array(states, dtype=np.int64)
+
+  def sample(self):
+    T = self.sample_length()
+    x = self.np_rng.choice(range(self.n_generators), p=self.perm_probs, size=T) + self.vocab_size
+    
+    i = 0
+    reset_in = 0 # always start with reset
+    while i < T:
+        if reset_in == 0:
+            x[i] = self.np_rng.choice(range(self.vocab_size))
+            i += self.np_rng.choice(self.lags)
+    
+    return x, self.f(x)
 
 
 
@@ -714,6 +762,7 @@ dataset_map = {
   'parity': ParitySampler,
   'quaternion': QuaternionSampler,
   'symmetric': SymmetricSampler,
+  'permutation_reset': PermutationResetSampler
   # TODO: add Dyck
   }