Merge pull request #118 from kengz/policy-gradient

ActorCritic and DDPG

Author: kengz

rl/agent/actor_critic.py

@@ -0,0 +1,139 @@
+import numpy as np
+from rl.agent.dqn import DQN
+from rl.util import logger
+
+
+class ActorCritic(DQN):
+
+    '''
+    Actor Critic algorithm. The actor's policy
+    is adjusted in the direction that will lead to
+    better actions, guided by the critic
+    Implementation adapted from
+    http://www.rage.net/~greg/2016-07-05-ActorCritic-with-OpenAI-Gym.html
+
+    Assumes one of the policies in actor_critic.py are being used
+    '''
+
+    def __init__(self, env_spec,
+                 train_per_n_new_exp=1,
+                 gamma=0.95, lr=0.1,
+                 epi_change_lr=None,
+                 batch_size=16, n_epoch=5, hidden_layers=None,
+                 hidden_layers_activation='sigmoid',
+                 output_layer_activation='linear',
+                 auto_architecture=False,
+                 num_hidden_layers=3,
+                 first_hidden_layer_size=256,
+                 num_initial_channels=16,
+                 **kwargs):  # absorb generic param without breaking
+        # import only when needed to contain side-effects
+        from keras.layers.core import Dense
+        from keras.models import Sequential, load_model
+        self.Dense = Dense
+        self.Sequential = Sequential
+        self.load_model = load_model
+
+        super(ActorCritic, self).__init__(env_spec,
+                                          train_per_n_new_exp,
+                                          gamma, lr,
+                                          epi_change_lr,
+                                          batch_size, n_epoch, hidden_layers,
+                                          hidden_layers_activation,
+                                          output_layer_activation,
+                                          auto_architecture,
+                                          num_hidden_layers,
+                                          first_hidden_layer_size,
+                                          num_initial_channels,
+                                          **kwargs)
+
+    def build_model(self):
+        self.build_actor()
+        self.build_critic()
+        logger.info("Actor and critic models built")
+
+    def build_actor(self):
+        actor = self.Sequential()
+        super(ActorCritic, self).build_hidden_layers(actor)
+        actor.add(self.Dense(self.env_spec['action_dim'],
+                             init='lecun_uniform',
+                             activation=self.output_layer_activation))
+        logger.info("Actor summary")
+        actor.summary()
+        self.actor = actor
+
+    def build_critic(self):
+        critic = self.Sequential()
+        super(ActorCritic, self).build_hidden_layers(critic)
+        critic.add(self.Dense(1,
+                              init='lecun_uniform',
+                              activation=self.output_layer_activation))
+        logger.info("Critic summary")
+        critic.summary()
+        self.critic = critic
+
+    def compile_model(self):
+        self.actor.compile(
+            loss='mse',
+            optimizer=self.optimizer.keras_optimizer)
+        self.critic.compile(
+            loss='mse',
+            optimizer=self.optimizer.keras_optimizer)
+        logger.info("Actor and critic compiled")
+
+    def recompile_model(self, sys_vars):
+        '''
+        Option to change model optimizer settings
+        Currently only used for changing the learning rate
+        Compiling does not affect the model weights
+        '''
+        if self.epi_change_lr is not None:
+            if (sys_vars['epi'] == self.epi_change_lr and
+                    sys_vars['t'] == 0):
+                self.lr = self.lr / 10.0
+                self.optimizer.change_optim_param(**{'lr': self.lr})
+                self.actor.compile(
+                    loss='mse',
+                    optimizer=self.optimizer.keras_optimizer)
+                self.critic.compile(
+                    loss='mse',
+                    optimizer=self.optimizer.keras_optimizer)
+                logger.info(
+                    'Actor and critic models recompiled with new settings: '
+                    'Learning rate: {}'.format(self.lr))
+
+    def train_critic(self, minibatch):
+        Q_vals = np.clip(self.critic.predict(minibatch['states']),
+                         -self.clip_val, self.clip_val)
+        Q_next_vals = np.clip(self.critic.predict(minibatch['next_states']),
+                              -self.clip_val, self.clip_val)
+        Q_targets = minibatch['rewards'] + self.gamma * \
+            (1 - minibatch['terminals']) * Q_next_vals.squeeze()
+        Q_targets = np.expand_dims(Q_targets, axis=1)
+
+        actor_delta = Q_next_vals - Q_vals
+        loss = self.critic.train_on_batch(minibatch['states'], Q_targets)
+
+        errors = abs(np.sum(Q_vals - Q_targets, axis=1))
+        self.memory.update(errors)
+        return loss, actor_delta
+
+    def train_actor(self, minibatch, actor_delta):
+        old_vals = self.actor.predict(minibatch['states'])
+        if self.env_spec['actions'] == 'continuous':
+            A_targets = np.zeros(
+                (actor_delta.shape[0], self.env_spec['action_dim']))
+            for j in range(A_targets.shape[1]):
+                A_targets[:, j] = actor_delta.squeeze()
+        else:
+            A_targets = minibatch['actions'] * actor_delta + \
+                (1 - minibatch['actions']) * old_vals
+
+        loss = self.actor.train_on_batch(minibatch['states'], A_targets)
+        return loss
+
+    def train_an_epoch(self):
+        minibatch = self.memory.rand_minibatch(self.batch_size)
+        critic_loss, actor_delta = self.train_critic(minibatch)
+        actor_loss = self.train_actor(minibatch, actor_delta)
+        return critic_loss + actor_loss