[RLlib]: Fix FQE Policy call (#26671)

rllib/offline/estimators/fqe_torch_model.py

@@ -110,8 +110,9 @@ class FQETorchModel:
             A list of losses for each training iteration
         """
         losses = []
-        if self.minibatch_size is None:
-            minibatch_size = batch.count
+        minibatch_size = self.minibatch_size or batch.count
+        # Copy batch for shuffling
+        batch = batch.copy(shallow=True)
         for _ in range(self.n_iters):
             minibatch_losses = []
             batch.shuffle()
@@ -209,18 +210,29 @@ class FQETorchModel:
         input_dict = {SampleBatch.OBS: obs}
         seq_lens = torch.ones(len(obs), device=self.device, dtype=int)
         state_batches = []
-        if self.policy.action_distribution_fn and is_overridden(
-            self.policy.action_distribution_fn
-        ):
-            dist_inputs, dist_class, _ = self.policy.action_distribution_fn(
-                self.policy,
-                self.policy.model,
-                input_dict=input_dict,
-                state_batches=state_batches,
-                seq_lens=seq_lens,
-                explore=False,
-                is_training=False,
-            )
+        if is_overridden(self.policy.action_distribution_fn):
+            try:
+                # TorchPolicyV2 function signature
+                dist_inputs, dist_class, _ = self.policy.action_distribution_fn(
+                    self.policy.model,
+                    obs_batch=input_dict,
+                    state_batches=state_batches,
+                    seq_lens=seq_lens,
+                    explore=False,
+                    is_training=False,
+                )
+            except TypeError:
+                # TorchPolicyV1 function signature for compatibility with DQN
+                # TODO: Remove this once DQNTorchPolicy is migrated to PolicyV2
+                dist_inputs, dist_class, _ = self.policy.action_distribution_fn(
+                    self.policy,
+                    self.policy.model,
+                    input_dict=input_dict,
+                    state_batches=state_batches,
+                    seq_lens=seq_lens,
+                    explore=False,
+                    is_training=False,
+                )
         else:
             dist_class = self.policy.dist_class
             dist_inputs, _ = self.policy.model(input_dict, state_batches, seq_lens)

rllib/offline/estimators/tests/test_ope.py

@@ -10,10 +10,14 @@ from ray.rllib.offline.estimators import (
 from ray.rllib.offline.estimators.fqe_torch_model import FQETorchModel
 from ray.rllib.offline.json_reader import JsonReader
 from ray.rllib.policy.sample_batch import concat_samples
+from ray.rllib.utils.test_utils import check
+from ray.rllib.utils.numpy import convert_to_numpy
 from pathlib import Path
 import os
+import copy
 import numpy as np
 import gym
+import torch
 
 
 class TestOPE(unittest.TestCase):
@@ -162,6 +166,48 @@ class TestOPE(unittest.TestCase):
         print(*list(std_est.items()), sep="\n")
         print("\n\n\n")
 
+    def test_fqe_model(self):
+        # Test FQETorchModel for:
+        # (1) Check that it does not modify the underlying batch during training
+        # (2) Check that the stoppign criteria from FQE are working correctly
+        # (3) Check that using fqe._compute_action_probs equals brute force
+        # iterating over all actions with policy.compute_log_likelihoods
+        fqe = FQETorchModel(
+            policy=self.algo.get_policy(),
+            gamma=self.gamma,
+            **self.q_model_config,
+        )
+        tmp_batch = copy.deepcopy(self.batch)
+        losses = fqe.train(self.batch)
+
+        # Make sure FQETorchModel.train() does not modify self.batch
+        check(tmp_batch, self.batch)
+
+        # Make sure FQE stopping criteria are respected
+        assert (
+            len(losses) == fqe.n_iters or losses[-1] < fqe.delta
+        ), f"FQE.train() terminated early in {len(losses)} steps with final loss"
+        f"{losses[-1]} for n_iters: {fqe.n_iters} and delta: {fqe.delta}"
+
+        # Test fqe._compute_action_probs against "brute force" method
+        # of computing log_prob for each possible action individually
+        # using policy.compute_log_likelihoods
+        obs = torch.tensor(self.batch["obs"], device=fqe.device)
+        action_probs = fqe._compute_action_probs(obs)
+        action_probs = convert_to_numpy(action_probs)
+
+        tmp_probs = []
+        for act in range(fqe.policy.action_space.n):
+            tmp_actions = np.zeros_like(self.batch["actions"]) + act
+            log_probs = fqe.policy.compute_log_likelihoods(
+                actions=tmp_actions,
+                obs_batch=self.batch["obs"],
+            )
+            tmp_probs.append(torch.exp(log_probs))
+        tmp_probs = torch.stack(tmp_probs).transpose(0, 1)
+        tmp_probs = convert_to_numpy(tmp_probs)
+        check(action_probs, tmp_probs, decimals=3)
+
     def test_multiple_inputs(self):
         # TODO (Rohan138): Test with multiple input files
         pass