class DQNAgent:
def __init__(self):
self.action_space = env.action_space.n # number of actions
self.discount_rate = 0.99
self.stack_frames = 4 # number of frames stacked
self.lr = 2.5e-5
self.model = self.build_deep_q_model() # build the main network
self.target_model = self.build_deep_q_model(
) # build the target network
mask_shape = (1, env.action_space.n)
self.batch_size = 32 # number of batches to learn from
self.priority_replay_size = 1000000 # max replay memory size
self.priority_replay = Memory(
self.priority_replay_size) # create the replay memory
self.exploration_rate = AnnealingVariable(
1., .01,
400000) # exploration rate (start_value, final_value, n_steps)
self.mask = np.ones(
mask_shape, dtype=np.float32
) # mask used in the training to train only the q values for which the agent performed and action
self.one_hot = np.eye(env.action_space.n, dtype=np.float32)
self.update_target_frequency = 10000 # update target every
self.replay_frequency = 4 # learn from memories frequency
# creates the network and returns it
def build_deep_q_model(self, image_size: tuple = (84, 84)) -> keras.Model:
# weights initializer - he init
initializer = keras.initializers.VarianceScaling(scale=2.0)
# input layer - takes (84,84,84,4) images
cnn_input = keras.layers.Input((*image_size, self.stack_frames),
name="cnninpt")
# mask input - one hot when want only q_value for particular action
mask_input = keras.layers.Input((self.action_space, ), name="mask")
# first Conv2D layer
cnn = keras.layers.Conv2D(32,
8,
strides=4,
activation="relu",
padding='valid',
kernel_initializer=initializer)(cnn_input)
# second Conv2D layer
cnn = keras.layers.Conv2D(64,
4,
strides=2,
activation="relu",
padding='valid',
kernel_initializer=initializer)(cnn)
# third Conv2D layer
cnn = keras.layers.Conv2D(64,
3,
strides=1,
activation="relu",
padding='valid',
kernel_initializer=initializer)(cnn)
# flatten the kernels from previous layers
cnn = keras.layers.Flatten()(cnn)
# fully connected layer
cnn = keras.layers.Dense(512,
activation="relu",
kernel_initializer=initializer)(cnn)
# output layer, q_values for every action in enviroment
cnn = keras.layers.Dense(self.action_space, name="output")(cnn)
# multiply output by mask to give true output
output = keras.layers.Multiply()([cnn, mask_input])
# create the model
model = keras.Model(inputs=[cnn_input, mask_input], outputs=output)
# add loss function and method of optimization
model.compile(loss=huber_loss,
optimizer=keras.optimizers.Adam(lr=self.lr))
print(model.summary())
return model
# samples a batch of #batch_size from the priority replay
def sample(self):
batch = self.priority_replay.sample(
self.batch_size) # sample batch according to priorities
X_state = [None] * len(batch) # create empty list #batch_size
X_action = [None] * len(batch)
X_reward = [None] * len(batch)
X_done = [None] * len(batch)
X_next_state = [None] * len(batch)
# for each batch - retrieve the particualar entries
for i in range(len(batch)):
o = batch[i][1]
X_state[i] = np.array(o[0], copy=False)
X_action[i] = o[1]
X_reward[i] = o[2]
X_done[i] = o[3]
X_next_state[i] = np.array(o[4], copy=False)
return np.array(X_state), np.array(X_action), np.array(
X_reward), np.array(X_done), np.array(X_next_state), batch
# train on the samples in memory
def learn_from_memories(self):
X_state, X_action, X_reward, X_done, X_next_state, batch = self.sample(
)
# repeat the base mask (all actions) for all the samples in the batch
mask = np.repeat(self.mask, len(X_state), axis=0)
# q for the next_state is 0 if episode has ended or else the max of q values according to the target network
q_next = np.max(self.target_model.predict_on_batch(
[X_next_state, mask]),
axis=1)
q_next[X_done] = 0.0
# the q predictions on batch
pred = self.model.predict_on_batch([X_state, self.mask])
# the q predictions for each action taken only
pred_action = pred[range(pred.shape[0]), X_action]
# calculate the target / true values
target_q = X_reward + self.discount_rate * q_next
# get the error - priorirty
error = abs(target_q - pred_action)
# update errors - priorities
for i in range(len(batch)):
idx = batch[i][0]
self.priority_replay.update(idx, error[i])
# assign target_q to the appropriate true_q columns for which the agent performed an action
# all other true q values are 0 and the agent is not trained based on their value
true_q = np.zeros((len(X_state), env.action_space.n), dtype=np.float32)
# for every row, for the columns the agent picked that action assign target_q
true_q[range(true_q.shape[0]), X_action] = target_q
# train only on actions the agent chose - One hot mask from action batch
return self.model.fit([X_state, self.one_hot[X_action]],
true_q,
verbose=0,
epochs=1)
# helper function to initialize the priority replay with init_size samples
def init_priority_replay(self, init_size=50000):
while init_size > 0:
done = False
state = env.reset() # reset the env
while not done:
# behave randomly
action = env.action_space.sample()
next_state, reward, done, _ = env.step(action)
# save batch of experience to memory
self.save_to_memory(state, action, reward, done, next_state)
state = next_state
init_size -= 1
# takes the experience and stores it in replay memory
def save_to_memory(self, state, action, reward, done, next_state):
error = self.get_error(state, action, reward, done,
next_state) # find error - priority
self.priority_replay.add(
error, (state, action, reward, done,
next_state)) # save to memory according to priority
# behaves epsilon greedily
def epsilon_greedy_policy(self, state, epsilon=0.01):
if np.random.random() < epsilon:
return env.action_space.sample() # pick randomly
q_values = self.predict_qvalues(state)
return np.argmax(q_values) # pick optimal action - max q(s,a)
# calculate the error of prediction
def get_error(self, state, action, reward, done, next_state):
# q next is 0 for terminal states else predict it from target network
if done:
q_next = 0.0
else:
next_state = np.expand_dims(next_state, axis=0)
q_next = self.target_model.predict([next_state, self.mask])
predicted_q = self.predict_qvalues(state)
# error = true - predicted for action taken
error = abs(reward + self.discount_rate * np.max(q_next) -
predicted_q[0, action])
return error
# predicts and returns q values from state
def predict_qvalues(self, state: np.ndarray):
# keras needs first dimension to be batch size even if only one sample
state = np.expand_dims(state, axis=0)
return self.model.predict([state, self.mask])
# trains the agent for max_steps
def train_model(self, max_steps, stats):
print("Start Training ")
while max_steps > 0:
r_per_episode = 0
error = 0
done = False
state = env.reset()
while not done: # the episode has not ended
# find action according to epsilon greedy behaviour with epsilon = exploration rate
action = self.epsilon_greedy_policy(
state, self.exploration_rate.value)
# decrease the exploration rate
self.exploration_rate.step()
max_steps -= 1
# take the action and observe next observation, reward, done
next_state, reward, done, _ = env.step(action)
r_per_episode += reward
# save this experience to memory
self.save_to_memory(state, action, reward, done, next_state)
state = next_state
# time to train from priority replay
if max_steps % self.replay_frequency == 0:
hist = self.learn_from_memories()
error += hist.history['loss'][0]
# time to update the target network
if max_steps % self.update_target_frequency == 0:
self.target_model.set_weights(self.model.get_weights())
# update stats
stats(self, r_per_episode)
# save stats at the end of training
stats.save_stats()
# test the agent for nepisodes
def play(self, nepisodes, exploration_rate, stats):
rewards_arr = np.zeros(nepisodes)
for episode in range(nepisodes):
episode_reward = 0
done = False
state = env.reset()
while not done:
env.render()
# time.sleep(0.05)
action = self.epsilon_greedy_policy(state, exploration_rate)
next_state, reward, done, _ = env.step(action)
episode_reward += reward
state = next_state
rewards_arr[episode] = episode_reward
stats(self, episode_reward)
print(episode_reward)
stats.save_stats()
return rewards_arr
def save_weights(self):
print("PRINT")
self.model.save_weights("PongDQNWeights.h5")
def save_model(self):
self.model.save("DqnPongModel.h5")
def restore_weights(self):
print("Restoring model weights Pong")
self.model.load_weights("DqnPongModel.h5")
def train_thread(agent, max_eps, env, discount_rate, optimizer,
statistics: Stats, exploration_rate: AnnealingVariable,
number):
# create local network and init its weights equal to the global
local_network = Actor_Critic(env.action_space.n)
# prepare it (must do this when eager execution is enabled)
local_network(
tf.convert_to_tensor(np.random.random((1, 84, 84, 4)),
dtype=tf.float32))
local_network.set_weights(agent.global_network.get_weights())
# lr_decay_anneal = AnnealingVariable(1e-4, 1e-24, 10e6)
global episodes # number of total episodes done for all threads
# local lists for states, rewards and actions
states, rewards, actions = [], [], []
while episodes < max_eps:
r_per_episode = 0.0
done = False
step = 0
state = env.reset()
# still training
while not done and episodes < max_eps:
exploration_rate.step() # decay the exploration rate
states.append(
state) # add the observation/state into the state list
# find acction to pick according to the probs network and the exploration rate
action = pick_action(env, local_network, state,
exploration_rate.value)
# do the action and observe the next state, reward and if the episode is over
next_state, reward, done, _ = env.step(action)
# lr_decay_anneal.step()
# append the reward experienced in the reward list
rewards.append(reward)
# append action taken
actions.append(action)
r_per_episode += reward
step += 1
# if gathered enough experience or the episode is over -> train on experience gathered
if step % train_frequency == 0 or done:
# Gradient tape records the gradient during the evaluation of the loss function
# -> eager execution MUST be enabled to work
with tf.GradientTape() as tape:
# compute loss for each batch of experience
loss = compute_loss_from_batch(local_network, states,
rewards, actions, done,
next_state, discount_rate)
# rewind the tape and get the gradients of the loss
# for the weights of the local network (Actor-Critic)
gradients = tape.gradient(loss,
local_network.trainable_weights)
# used because multiple threads
lock.acquire()
# agent.lr.assign(lr_decay_anneal.value)
# apply the gradients found from the local network into the global network for the global weights
optimizer.apply_gradients(
zip(gradients, agent.global_network.trainable_weights))
# update local network with weights of global
local_network.set_weights(agent.global_network.get_weights())
lock.release()
# empty state, reward, action list
states, rewards, actions = [], [], []
state = next_state
with lock:
# save stats
if episodes < max_eps:
episodes += 1
statistics(agent, r_per_episode)