#625 fix entropy shape

src/imitation/algorithms/pebble/entropy_reward.py

@@ -94,7 +94,8 @@ def _entropy_reward(self, state, action, next_state, done):
         all_observations = all_observations.reshape((-1, *self.obs_shape))
 
         if all_observations.shape[0] < self.nearest_neighbor_k:
-            # not enough observations to compare to, fall back to the learned function
+            # not enough observations to compare to, fall back to the learned function;
+            # (falling back to a constant may also be ok)
             return self.learned_reward_fn(state, action, next_state, done)
         else:
             # TODO #625: deal with the conversion back and forth between np and torch
@@ -104,7 +105,7 @@ def _entropy_reward(self, state, action, next_state, done):
                 self.nearest_neighbor_k,
             )
             normalized_entropies = self.entropy_stats.forward(entropies)
-        return normalized_entropies.numpy()
+            return normalized_entropies.numpy()
 
     def __getstate__(self):
         state = self.__dict__.copy()

src/imitation/util/util.py

@@ -389,5 +389,4 @@ def compute_state_entropy(
         # a point is itself, which we want to skip.
         assert distances_tensor.shape[-1] > k
         knn_dists = th.kthvalue(distances_tensor, k=k + 1, dim=1).values
-        state_entropy = knn_dists
-    return state_entropy.unsqueeze(1)
+        return knn_dists

tests/algorithms/pebble/test_entropy_reward.py

@@ -21,20 +21,20 @@
 
 
 def test_pebble_entropy_reward_returns_entropy_for_pretraining(rng):
-    all_observations = rng.random((BUFFER_SIZE, VENVS, *(OBS_SHAPE)))
+    all_observations = rng.random((BUFFER_SIZE, VENVS, *OBS_SHAPE))
 
     reward_fn = PebbleStateEntropyReward(Mock(), K)
     reward_fn.set_replay_buffer(
         ReplayBufferView(all_observations, lambda: slice(None)), OBS_SHAPE
     )
 
     # Act
-    observations = th.rand((BATCH_SIZE, *(OBS_SHAPE)))
+    observations = th.rand((BATCH_SIZE, *OBS_SHAPE))
     reward = reward_fn(observations, PLACEHOLDER, PLACEHOLDER, PLACEHOLDER)
 
     # Assert
     expected = util.compute_state_entropy(
-        observations, all_observations.reshape(-1, *(OBS_SHAPE)), K
+        observations, all_observations.reshape(-1, *OBS_SHAPE), K
     )
     expected_normalized = reward_fn.entropy_stats.normalize(
         th.as_tensor(expected)