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import numpy as np
import abc
class AbstractReplayBuffer(abc.ABC):
@abc.abstractmethod
def add(self, time_step):
pass
@abc.abstractmethod
def __next__(self, ):
pass
@abc.abstractmethod
def __len__(self, ):
pass
class EfficientReplayBuffer(AbstractReplayBuffer):
'''Fast + efficient replay buffer implementation in numpy.'''
def __init__(self, buffer_size, batch_size, nstep, discount, frame_stack,
data_specs=None, sarsa=False):
self.buffer_size = buffer_size
self.data_dict = {}
self.index = -1
self.traj_index = 0
self.frame_stack = frame_stack
self._recorded_frames = frame_stack + 1
self.batch_size = batch_size
self.nstep = nstep
self.discount = discount
self.full = False
self.discount_vec = np.power(discount, np.arange(nstep)) # n_step - first dim should broadcast
self.next_dis = discount ** nstep
self.sarsa = sarsa
def _initial_setup(self, time_step):
self.index = 0
self.obs_shape = list(time_step.observation.shape)
self.ims_channels = self.obs_shape[0] // self.frame_stack
self.act_shape = time_step.action.shape
self.obs = np.zeros([self.buffer_size, self.ims_channels, *self.obs_shape[1:]], dtype=np.uint8)
self.act = np.zeros([self.buffer_size, *self.act_shape], dtype=np.float32)
self.rew = np.zeros([self.buffer_size], dtype=np.float32)
self.dis = np.zeros([self.buffer_size], dtype=np.float32)
self.valid = np.zeros([self.buffer_size], dtype=np.bool_)
def add_data_point(self, time_step):
first = time_step.first()
latest_obs = time_step.observation[-self.ims_channels:]
if first:
end_index = self.index + self.frame_stack
end_invalid = end_index + self.frame_stack + 1
if end_invalid > self.buffer_size:
if end_index > self.buffer_size:
end_index = end_index % self.buffer_size
self.obs[self.index:self.buffer_size] = latest_obs
self.obs[0:end_index] = latest_obs
self.full = True
else:
self.obs[self.index:end_index] = latest_obs
end_invalid = end_invalid % self.buffer_size
self.valid[self.index:self.buffer_size] = False
self.valid[0:end_invalid] = False
else:
self.obs[self.index:end_index] = latest_obs
self.valid[self.index:end_invalid] = False
self.index = end_index
self.traj_index = 1
else:
np.copyto(self.obs[self.index], latest_obs) # Check most recent image
np.copyto(self.act[self.index], time_step.action)
self.rew[self.index] = time_step.reward
self.dis[self.index] = time_step.discount
self.valid[(self.index + self.frame_stack) % self.buffer_size] = False
if self.traj_index >= self.nstep:
self.valid[(self.index - self.nstep + 1) % self.buffer_size] = True
self.index += 1
self.traj_index += 1
if self.index == self.buffer_size:
self.index = 0
self.full = True
def add(self, time_step):
if self.index == -1:
self._initial_setup(time_step)
self.add_data_point(time_step)
def __next__(self, ):
indices = np.random.choice(self.valid.nonzero()[0], size=self.batch_size)
return self.gather_nstep_indices(indices)
def gather_nstep_indices(self, indices):
n_samples = indices.shape[0]
all_gather_ranges = np.stack([np.arange(indices[i] - self.frame_stack, indices[i] + self.nstep)
for i in range(n_samples)], axis=0) % self.buffer_size
gather_ranges = all_gather_ranges[:, self.frame_stack:] # bs x nstep
obs_gather_ranges = all_gather_ranges[:, :self.frame_stack]
nobs_gather_ranges = all_gather_ranges[:, -self.frame_stack:]
all_rewards = self.rew[gather_ranges]
# Could implement below operation as a matmul in pytorch for marginal additional speed improvement
rew = np.sum(all_rewards * self.discount_vec, axis=1, keepdims=True)
obs = np.reshape(self.obs[obs_gather_ranges], [n_samples, *self.obs_shape])
nobs = np.reshape(self.obs[nobs_gather_ranges], [n_samples, *self.obs_shape])
act = self.act[indices]
dis = np.expand_dims(self.next_dis * self.dis[nobs_gather_ranges[:, -1]], axis=-1)
if self.sarsa:
nact = self.act[indices + self.nstep]
return (obs, act, rew, dis, nobs, nact)
return (obs, act, rew, dis, nobs)
def __len__(self):
if self.full:
return self.buffer_size
else:
return self.index
def get_train_and_val_indices(self, validation_percentage):
all_indices = self.valid.nonzero()[0]
num_indices = all_indices.shape[0]
num_val = int(num_indices * validation_percentage)
np.random.shuffle(all_indices)
val_indices, train_indices = np.split(all_indices,
[num_val])
return train_indices, val_indices
def get_obs_act_batch(self, indices):
n_samples = indices.shape[0]
obs_gather_ranges = np.stack([np.arange(indices[i] - self.frame_stack, indices[i])
for i in range(n_samples)], axis=0) % self.buffer_size
obs = np.reshape(self.obs[obs_gather_ranges], [n_samples, *self.obs_shape])
act = self.act[indices]
return obs, act
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