class Agent():
"""Interacts with and learns from the environment."""
def __init__(self, state_size, action_size):
"""Initialize an Agent object.
Params
======
state_size (int): dimension of each state
action_size (int): dimension of each action
seed (int): random seed
"""
self.state_size = state_size
self.action_size = action_size
# Q-Network
self.qnetwork_local = QNetwork(state_size, action_size).to(device)
self.qnetwork_target = QNetwork(state_size, action_size).to(device)
self.optimizer = optim.Adam(self.qnetwork_local.parameters(), lr=LR)
# Replay memory
self.memory = ReplayBuffer(action_size, BUFFER_SIZE, BATCH_SIZE)
# Initialize time step (for updating every UPDATE_EVERY steps)
self.t_step = 0
def step(self, state, action, reward, next_state, done):
# Save experience in replay memory
self.memory.add(state, action, reward, next_state, done)
# Learn every UPDATE_EVERY time steps.
self.t_step = (self.t_step + 1) % UPDATE_EVERY
if self.t_step == 0:
# If enough samples are available in memory, get random subset and learn
if len(self.memory) > BATCH_SIZE:
experiences = self.memory.sample()
self.learn(experiences, GAMMA)
def act(self, state, eps=0.):
"""Returns actions for given state as per current policy.
Params
======
state (array_like): current state
eps (float): epsilon, for epsilon-greedy action selection
"""
state = torch.from_numpy(state).float().unsqueeze(0).to(device)
self.qnetwork_local.eval()
with torch.no_grad():
action_values = self.qnetwork_local(state)
self.qnetwork_local.train()
# Epsilon-greedy action selection
if random.random() > eps:
return np.argmax(action_values.cpu().data.numpy())
else:
return random.choice(np.arange(self.action_size))
def learn(self, experiences, gamma):
"""Update value parameters using given batch of experience tuples.
Params
======
experiences (Tuple[torch.Variable]): tuple of (s, a, r, s', done) tuples
gamma (float): discount factor
"""
states, actions, rewards, next_states, dones = experiences
states = torch.from_numpy(states).float().to(device)
actions = torch.from_numpy(actions).long().to(device)
rewards = torch.from_numpy(rewards).float().to(device)
next_states = torch.from_numpy(next_states).float().to(device)
dones = torch.from_numpy(dones).float().to(device)
# Get max predicted Q values (for next states) from target model
Q_targets_next = self.qnetwork_target(next_states).detach().max(
1)[0].unsqueeze(1)
# Compute Q targets for current states
Q_targets = rewards + (gamma * Q_targets_next * (1 - dones))
# Get expected Q values from local model
Q_expected = self.qnetwork_local(states).gather(1, actions)
# Compute loss
loss = F.mse_loss(Q_expected, Q_targets)
# Minimize the loss
self.optimizer.zero_grad()
loss.backward()
self.optimizer.step()
# ------------------- update target network ------------------- #
self.soft_update(self.qnetwork_local, self.qnetwork_target, TAU)
def soft_update(self, local_model, target_model, tau):
"""Soft update model parameters.
θ_target = τ*θ_local + (1 - τ)*θ_target
Params
======
local_model (PyTorch model): weights will be copied from
target_model (PyTorch model): weights will be copied to
tau (float): interpolation parameter
"""
for target_param, local_param in zip(target_model.parameters(),
local_model.parameters()):
target_param.data.copy_(tau * local_param.data +
(1.0 - tau) * target_param.data)
class Agent:
"""Interacts with and learns from the environment."""
def __init__(self, state_size, action_size, seed):
"""Initialize an Agent object.
Params
======
state_size (int): dimension of each state
action_size (int): dimension of each action
seed (int): random seed
"""
self.state_size = state_size
self.action_size = action_size
self.seed = random.seed(seed)
# Q-Network
self.qnetwork_local = QNetwork(state_size, action_size,
seed).to(device)
self.qnetwork_target = QNetwork(state_size, action_size,
seed).to(device)
self.optimizer = optim.Adam(self.qnetwork_local.parameters(), lr=LR)
# Replay memory
self.memory = ReplayBuffer(action_size, BUFFER_SIZE, BATCH_SIZE, seed)
# Initialize time step (for updating every UPDATE_EVERY steps)
self.t_step = 0
def step(self, state, action, reward, next_state, done):
# Save experience in replay memory
self.memory.add(state, action, reward, next_state, done)
# Learn every UPDATE_EVERY time steps.
self.t_step = (self.t_step + 1) % UPDATE_EVERY
if self.t_step == 0:
# If enough samples are available in memory, get random subset and learn
if len(self.memory) > BATCH_SIZE:
experiences = self.memory.sample()
self.learn(experiences, GAMMA)
def act(self, state, eps=0.):
"""Returns actions for given state as per current policy.
Params
======
state (array_like): current state
eps (float): epsilon, for epsilon-greedy action selection
"""
state = torch.from_numpy(state).float().unsqueeze(0).to(device)
self.qnetwork_local.eval()
with torch.no_grad():
action_values = self.qnetwork_local(state)
self.qnetwork_local.train()
# Epsilon-greedy action selection
if random.random() > eps:
return np.argmax(action_values.cpu().data.numpy())
else:
return random.choice(np.arange(self.action_size))
def learn(self, experiences, gamma):
"""Update value parameters using given batch of experience tuples.
Params
======
experiences (Tuple[torch.Variable]): tuple of (s, a, r, s', done) tuples
gamma (float): discount factor
"""
def loss_dqn(output, target):
loss = target - output
return (target - output)**2
states, actions, rewards, next_states, dones = experiences
# Reset gradients
# Calculate the value of the target in the next state
pred = self.qnetwork_target(next_states) # (64, 4)
target = rewards # (64, 1)
for i in range(BATCH_SIZE):
# Check for dones
if dones[i] == False:
target[i] = rewards[i] + GAMMA * torch.max(pred[i])
# The loss
output = self.qnetwork_local(states)
# Use gather in order to have the correct slicing
output_action_value = output.gather(1, actions.view(-1, 1))
loss = loss_dqn(output_action_value, target).mean()
# Reset gradients
self.optimizer.zero_grad()
loss.backward()
self.optimizer.step()
# ------------------- update target network ------------------- #
self.soft_update(self.qnetwork_local, self.qnetwork_target, TAU)
def soft_update(self, local_model, target_model, tau):
"""Soft update model parameters.
θ_target = τ*θ_local + (1 - τ)*θ_target
Params
======
local_model (PyTorch model): weights will be copied from
target_model (PyTorch model): weights will be copied to
tau (float): interpolation parameter
"""
for target_param, local_param in zip(target_model.parameters(),
local_model.parameters()):
target_param.data.copy_(tau * local_param.data +
(1.0 - tau) * target_param.data)
class Agent():
'''Interacts and learns from the environment'''
def __init__(self, state_size, action_size, seed):
"""Initialize an Agent object
Params
======
state_size (int): dimension of each state
action_size (int): dimension of each action
seed(int): random seed
"""
self.state_size = state_size
self.action_size = action_size
self.seed = random.seed(seed)
# Q-Network
self.qnetwork_local = QNetwork(state_size, action_size, seed).to(device)
self.qnetwork_target = QNetwork(state_size, action_size, seed).to(device)
self.optimizer = optim.Adam(self.qnetwork_local.parameters(), lr=LR)
# Replay memory
self.memory = ReplayBuffer(action_size, BUFFER_SIZE, BATCH_SIZE, seed)
# initialise the timestep (for updating every UPDATE_EVERY steps)
self.t_step = 0
def step(self, state, action, reward, next_state, done):
# Save experience in the replay memory
self.memory.add(state, action, reward, next_state, done)
# Learn every UPDATE_EVERY time steps
self.t_step = (self.t_step +1) % UPDATE_EVERY
if self.t_step ==0:
# Get random subset from the memory, but ONLY if there are enough samples
if len(self.memory) > BATCH_SIZE:
experiences = self.memory.sample()
self.learn(experiences, GAMMA)
def act(self, state, eps=0.):
"""Returns actions for given state as per current policy
Params
------
state(array_like): current state
eps(float): epsilon, epsilon-greedy action selection (to keep element of exploration)
"""
# convert the state from the Unity network into a torch tensor
state = torch.from_numpy(state).float().unsqueeze(0).to(device)
# Note to pass it through the deep network, we need to take the numpy array and:
# 1 - convert it to torch array with from_numpy()
# 2 - convert it to float 32 as that is what is expected. Use .float()
# 3 - Add a dimension on axis 0 with .unsqueeze(0). Because pytorch expects a BATCH of 1 dimensional arrays
# to be fed into its network. For example feeding in a batch of 64 arrays, each of length 37. In our case,
# with reinforcement learning we are only feeding one at a time, but the network still expects it to be 2D.
self.qnetwork_local.eval()
with torch.no_grad():
action_values = self.qnetwork_local(state)
self.qnetwork_local.train()
# Epsilon-greedy action selection
if random.random() > eps:
return np.argmax(action_values.cpu().data.numpy())
else:
return random.choice(np.arange(self.action_size))
def learn(self, experiences, gamma):
"""Update value paratmers of the deep-Q network using given batch of experience tuples
Params
------
experiences (Tuple[torch.Variable]): tuple of (s, a, r, s', done) tuples
gamma (float): discount factor
"""
states, actions, rewards, next_states, dones = experiences
# get the max predicted Q values for the next states, from the target model
# note: detach just detaches the tensor from the grad_fn - i.e. we are going to do some non-tracked
# computations based on the value of this tensor (we DON'T update the target model at this stage)
Q_targets_next = self.qnetwork_target(next_states).detach().max(1)[0].unsqueeze(1)
# compute Q targets for current states
Q_targets = rewards + (gamma * Q_targets_next * (1-dones))
# Get expected Q values from local model
Q_expected = self.qnetwork_local(states).gather(1, actions)
# compute loss
loss = F.mse_loss(Q_expected, Q_targets)
# Minimise the loss
self.optimizer.zero_grad()
loss.backward()
self.optimizer.step()
# update target network
self.soft_update(self.qnetwork_local, self.qnetwork_target, TAU)
def soft_update(self, local_model, target_model, tau):
"""Soft update model parameters
θ_target = τ*θ_local + (1 - τ)*θ_target
Params
======
local_model (Pytorch model): weights will be copied from
taret_model (Pytorch model): weights will be copied to
tau (float): interpolation parameter
"""
for target_param, local_param in zip(target_model.parameters(), local_model.parameters()):
target_param.data.copy_(tau*local_param.data + (1.0-tau) * target_param.data)
class Agent(object):
def __init__(self, state_size, action_size, seed, config):
self.state_size = state_size
self.action_size = action_size
self.config = config
self.seed = random.seed(seed)
self.local_q_net = QNetwork(state_size, action_size, seed).to(device)
self.target_q_net = QNetwork(state_size, action_size, seed).to(device)
self.optimizer = optim.Adam(self.local_q_net.parameters(),
lr=config["LR"])
self.memory = ReplayBuffer(action_size, config["BUFFER_SIZE"],
config["BATCH_SIZE"], seed)
self.t_step = 0
def step(self, state, action, reward, next_state, done):
self.memory.add(state, action, reward, next_state, done)
self.t_step = (self.t_step + 1) % self.config["UPDATE_EVERY"]
if self.t_step == 0:
# if agent experienced enough
if len(self.memory) > self.config["BATCH_SIZE"]:
experiences = self.memory.sample()
# Learn from previous experiences
self.learn(experiences, self.config["GAMMA"])
def act(self, state, eps=0.0):
state = torch.from_numpy(state).float().unsqueeze(0).to(device)
self.local_q_net.eval()
with torch.no_grad():
action_values = self.local_q_net(state)
self.local_q_net.train()
if random.random() > eps:
return np.argmax(action_values.cpu().data.numpy())
else:
return random.choice(np.arange(self.action_size))
def learn(self, experiences, gamma):
# Double Q Learning
states, actions, rewards, next_states, dones = experiences
# Get next action estimation with local q network
q_targets_next_expected = self.local_q_net(next_states).detach()
q_targets_next_expected_actions = q_targets_next_expected.max(
1)[1].unsqueeze(1)
# Calculate Next Targets
q_targets_next = self.target_q_net(next_states).gather(
1, q_targets_next_expected_actions)
# Non over-estimated targets
q_targets = rewards + (gamma * q_targets_next * (1 - dones))
# Expected value
q_expected = self.local_q_net(states).gather(1, actions)
loss = torch.nn.functional.mse_loss(q_expected, q_targets)
self.optimizer.zero_grad()
loss.backward()
self.optimizer.step()
self.soft_update(self.local_q_net, self.target_q_net,
self.config["TAU"])
def soft_update(self, local_net, target_net, tau):
for target_param, local_param in zip(target_net.parameters(),
local_net.parameters()):
target_param.data.copy_(tau * local_param.data +
(1 - tau) * target_param.data)