mirror of
https://github.com/labmlai/annotated_deep_learning_paper_implementations.git
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253 lines
9.1 KiB
Python
253 lines
9.1 KiB
Python
"""
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---
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title: DQN Experiment with Atari Breakout
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summary: Implementation of DQN experiment with Atari Breakout
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---
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# DQN Experiment with Atari Breakout
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This experiment trains a Deep Q Network (DQN) to play Atari Breakout game on OpenAI Gym.
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It runs the [game environments on multiple processes](../game.html) to sample efficiently.
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"""
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import numpy as np
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import torch
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from labml import tracker, experiment, logger, monit
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from labml_helpers.schedule import Piecewise
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from labml_nn.rl.dqn import QFuncLoss
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from labml_nn.rl.dqn.model import Model
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from labml_nn.rl.dqn.replay_buffer import ReplayBuffer
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from labml_nn.rl.game import Worker
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# Select device
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if torch.cuda.is_available():
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device = torch.device("cuda:0")
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else:
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device = torch.device("cpu")
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def obs_to_torch(obs: np.ndarray) -> torch.Tensor:
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"""Scale observations from `[0, 255]` to `[0, 1]`"""
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return torch.tensor(obs, dtype=torch.float32, device=device) / 255.
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class Trainer:
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"""
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## Trainer
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"""
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def __init__(self):
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# #### Configurations
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# number of workers
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self.n_workers = 8
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# steps sampled on each update
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self.worker_steps = 4
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# number of training iterations
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self.train_epochs = 8
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# number of updates
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self.updates = 1_000_000
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# size of mini batch for training
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self.mini_batch_size = 32
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# exploration as a function of updates
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self.exploration_coefficient = Piecewise(
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[
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(0, 1.0),
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(25_000, 0.1),
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(self.updates / 2, 0.01)
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], outside_value=0.01)
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# update target network every 250 update
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self.update_target_model = 250
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# $\beta$ for replay buffer as a function of updates
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self.prioritized_replay_beta = Piecewise(
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[
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(0, 0.4),
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(self.updates, 1)
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], outside_value=1)
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# Replay buffer with $\alpha = 0.6$. Capacity of the replay buffer must be a power of 2.
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self.replay_buffer = ReplayBuffer(2 ** 14, 0.6)
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# Model for sampling and training
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self.model = Model().to(device)
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# target model to get $\color{orange}Q(s';\color{orange}{\theta_i^{-}})$
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self.target_model = Model().to(device)
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# create workers
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self.workers = [Worker(47 + i) for i in range(self.n_workers)]
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# initialize tensors for observations
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self.obs = np.zeros((self.n_workers, 4, 84, 84), dtype=np.uint8)
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for worker in self.workers:
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worker.child.send(("reset", None))
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for i, worker in enumerate(self.workers):
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self.obs[i] = worker.child.recv()
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# loss function
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self.loss_func = QFuncLoss(0.99)
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# optimizer
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self.optimizer = torch.optim.Adam(self.model.parameters(), lr=2.5e-4)
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def _sample_action(self, q_value: torch.Tensor, exploration_coefficient: float):
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"""
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#### $\epsilon$-greedy Sampling
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When sampling actions we use a $\epsilon$-greedy strategy, where we
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take a greedy action with probabiliy $1 - \epsilon$ and
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take a random action with probability $\epsilon$.
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We refer to $\epsilon$ as `exploration_coefficient`.
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"""
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# Sampling doesn't need gradients
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with torch.no_grad():
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# Sample the action with highest Q-value. This is the greedy action.
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greedy_action = torch.argmax(q_value, dim=-1)
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# Uniformly sample and action
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random_action = torch.randint(q_value.shape[-1], greedy_action.shape, device=q_value.device)
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# Whether to chose greedy action or the random action
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is_choose_rand = torch.rand(greedy_action.shape, device=q_value.device) < exploration_coefficient
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# Pick the action based on `is_choose_rand`
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return torch.where(is_choose_rand, random_action, greedy_action).cpu().numpy()
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def sample(self, exploration_coefficient: float):
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"""### Sample data"""
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# This doesn't need gradients
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with torch.no_grad():
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# Sample `worker_steps`
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for t in range(self.worker_steps):
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# Get Q_values for the current observation
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q_value = self.model(obs_to_torch(self.obs))
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# Sample actions
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actions = self._sample_action(q_value, exploration_coefficient)
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# Run sampled actions on each worker
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for w, worker in enumerate(self.workers):
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worker.child.send(("step", actions[w]))
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# Collect information from each worker
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for w, worker in enumerate(self.workers):
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# Get results after executing the actions
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next_obs, reward, done, info = worker.child.recv()
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# Add transition to replay buffer
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self.replay_buffer.add(self.obs[w], actions[w], reward, next_obs, done)
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# update episode information
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# collect episode info, which is available if an episode finished;
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# this includes total reward and length of the episode -
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# look at `Game` to see how it works.
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if info:
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tracker.add('reward', info['reward'])
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tracker.add('length', info['length'])
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# update current observation
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self.obs[w] = next_obs
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def train(self, beta: float):
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"""
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### Train the model
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"""
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for _ in range(self.train_epochs):
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# Sample from priority replay buffer
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samples = self.replay_buffer.sample(self.mini_batch_size, beta)
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# Get the predicted Q-value
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q_value = self.model(obs_to_torch(samples['obs']))
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# Get the Q-values of the next state for [Double Q-learning](index.html).
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# Gradients shouldn't propagate for these
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with torch.no_grad():
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# Get $\color{cyan}Q(s';\color{cyan}{\theta_i})$
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double_q_value = self.model(obs_to_torch(samples['next_obs']))
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# Get $\color{orange}Q(s';\color{orange}{\theta_i^{-}})$
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target_q_value = self.target_model(obs_to_torch(samples['next_obs']))
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# Compute Temporal Difference (TD) errors, $\delta$, and the loss, $\mathcal{L}(\theta)$.
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td_errors, loss = self.loss_func(q_value,
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q_value.new_tensor(samples['action']),
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double_q_value, target_q_value,
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q_value.new_tensor(samples['done']),
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q_value.new_tensor(samples['reward']),
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q_value.new_tensor(samples['weights']))
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# Calculate priorities for replay buffer $p_i = |\delta_i| + \epsilon$
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new_priorities = np.abs(td_errors.cpu().numpy()) + 1e-6
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# Update replay buffer priorities
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self.replay_buffer.update_priorities(samples['indexes'], new_priorities)
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# Zero out the previously calculated gradients
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self.optimizer.zero_grad()
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# Calculate gradients
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loss.backward()
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# Clip gradients
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torch.nn.utils.clip_grad_norm_(self.model.parameters(), max_norm=0.5)
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# Update parameters based on gradients
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self.optimizer.step()
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def run_training_loop(self):
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"""
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### Run training loop
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"""
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# Last 100 episode information
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tracker.set_queue('reward', 100, True)
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tracker.set_queue('length', 100, True)
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# Copy to target network initially
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self.target_model.load_state_dict(self.model.state_dict())
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for update in monit.loop(self.updates):
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# $\epsilon$, exploration fraction
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exploration = self.exploration_coefficient(update)
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tracker.add('exploration', exploration)
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# $\beta$ for prioritized replay
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beta = self.prioritized_replay_beta(update)
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tracker.add('beta', beta)
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# Sample with current policy
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self.sample(exploration)
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# Start training after the buffer is full
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if self.replay_buffer.is_full():
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# Train the model
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self.train(beta)
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# Periodically update target network
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if update % self.update_target_model == 0:
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self.target_model.load_state_dict(self.model.state_dict())
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# Save tracked indicators.
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tracker.save()
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# Add a new line to the screen periodically
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if (update + 1) % 1_000 == 0:
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logger.log()
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def destroy(self):
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"""
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### Destroy
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Stop the workers
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"""
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for worker in self.workers:
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worker.child.send(("close", None))
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def main():
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# Create the experiment
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experiment.create(name='dqn')
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# Initialize the trainer
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m = Trainer()
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# Run and monitor the experiment
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with experiment.start():
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m.run_training_loop()
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# Stop the workers
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m.destroy()
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# ## Run it
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if __name__ == "__main__":
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main()
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