Enable GAIL to decay

ml-agents/mlagents/trainers/ppo/optimizer_torch.py

         }
 
         for reward_provider in self.reward_signals.values():
-            update_stats.update(reward_provider.update(batch))
+            update_stats.update(
+                reward_provider.update(batch, self.policy.get_current_step())
+            )
 
         return update_stats
 

ml-agents/mlagents/trainers/sac/optimizer_torch.py

         return update_stats
 
     def update_reward_signals(
-        self, reward_signal_minibatches: Mapping[str, AgentBuffer], num_sequences: int
+        self,
+        reward_signal_minibatches: Mapping[str, AgentBuffer],
+        num_sequences: int,
+        global_step: int,
-            update_stats.update(self.reward_signals[name].update(update_buffer))
+            update_stats.update(
+                self.reward_signals[name].update(
+                    update_buffer, self.policy.get_current_step()
+                )
+            )
         return update_stats
 
     def get_modules(self):

ml-agents/mlagents/trainers/sac/trainer.py

                         sequence_length=self.policy.sequence_length,
                     )
             update_stats = self.optimizer.update_reward_signals(
-                reward_signal_minibatches, n_sequences
+                reward_signal_minibatches, n_sequences, self.step
             )
             for stat_name, value in update_stats.items():
                 batch_update_stats[stat_name].append(value)

ml-agents/mlagents/trainers/settings.py

 class GAILSettings(RewardSignalSettings):
     encoding_size: int = 64
     learning_rate: float = 3e-4
+    learning_rate_schedule: ScheduleType = ScheduleType.CONSTANT
+    decay_steps: int = 0
     use_actions: bool = False
     use_vail: bool = False
     demo_path: str = attr.ib(kw_only=True)

ml-agents/mlagents/trainers/torch/components/reward_providers/base_reward_provider.py

         )
 
     @abstractmethod
-    def update(self, mini_batch: AgentBuffer) -> Dict[str, np.ndarray]:
+    def update(
+        self, mini_batch: AgentBuffer, global_step: int
+    ) -> Dict[str, np.ndarray]:
+        :param global_step: The trainer's global step. Used to decay reward signals over time.
         :return: A dictionary from string to stats values
         """
         raise NotImplementedError(

ml-agents/mlagents/trainers/torch/components/reward_providers/curiosity_reward_provider.py

         rewards = np.minimum(rewards, 1.0 / self.strength)
         return rewards * self._has_updated_once
 
-    def update(self, mini_batch: AgentBuffer) -> Dict[str, np.ndarray]:
+    def update(
+        self, mini_batch: AgentBuffer, global_step: int
+    ) -> Dict[str, np.ndarray]:
         self._has_updated_once = True
         forward_loss = self._network.compute_forward_loss(mini_batch)
         inverse_loss = self._network.compute_inverse_loss(mini_batch)

ml-agents/mlagents/trainers/torch/components/reward_providers/extrinsic_reward_provider.py

     def evaluate(self, mini_batch: AgentBuffer) -> np.ndarray:
         return np.array(mini_batch[BufferKey.ENVIRONMENT_REWARDS], dtype=np.float32)
 
-    def update(self, mini_batch: AgentBuffer) -> Dict[str, np.ndarray]:
+    def update(
+        self, mini_batch: AgentBuffer, global_step: int
+    ) -> Dict[str, np.ndarray]:
         return {}

ml-agents/mlagents/trainers/torch/components/reward_providers/gail_reward_provider.py

             settings.demo_path, 1, specs
         )  # This is supposed to be the sequence length but we do not have access here
         params = list(self._discriminator_network.parameters())
+        self.decay_learning_rate = ModelUtils.DecayedValue(
+            settings.learning_rate_schedule,
+            settings.learning_rate,
+            1e-10,
+            settings.decay_steps,
+        )
         self.optimizer = torch.optim.Adam(params, lr=settings.learning_rate)
 
     def evaluate(self, mini_batch: AgentBuffer) -> np.ndarray:
                 )
             )
 
-    def update(self, mini_batch: AgentBuffer) -> Dict[str, np.ndarray]:
+    def update(
+        self, mini_batch: AgentBuffer, global_step: int
+    ) -> Dict[str, np.ndarray]:
+        decay_lr = self.decay_learning_rate.get_value(global_step)
         expert_batch = self._demo_buffer.sample_mini_batch(
             mini_batch.num_experiences, 1
         )
+        ModelUtils.update_learning_rate(self.optimizer, decay_lr)
         self.optimizer.zero_grad()
         loss.backward()
         self.optimizer.step()

ml-agents/mlagents/trainers/torch/components/reward_providers/rnd_reward_provider.py

             rewards = torch.sum((prediction - target) ** 2, dim=1)
         return rewards.detach().cpu().numpy()
 
-    def update(self, mini_batch: AgentBuffer) -> Dict[str, np.ndarray]:
+    def update(
+        self, mini_batch: AgentBuffer, global_step: int
+    ) -> Dict[str, np.ndarray]:
         with torch.no_grad():
             target = self._random_network(mini_batch)
         prediction = self._training_network(mini_batch)