class PrioritizedReplayBuffer(ReplayBuffer):
def __init__(self, size, alpha):
"""Create Prioritized Replay buffer.
Parameters
----------
size: int
Max number of transitions to store in the buffer. When the buffer
overflows the old memories are dropped.
alpha: float
how much prioritization is used
(0 - no prioritization, 1 - full prioritization)
See Also
--------
ReplayBuffer.__init__
"""
super(PrioritizedReplayBuffer, self).__init__(size)
assert alpha > 0
self._alpha = alpha
it_capacity = 1
while it_capacity < size:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
def add(self, *args, **kwargs):
"""See ReplayBuffer.store_effect"""
idx = self._next_idx
super().add(*args, **kwargs)
self._it_sum[idx] = self._max_priority ** self._alpha
self._it_min[idx] = self._max_priority ** self._alpha
def _sample_proportional(self, batch_size):
res = []
for _ in range(batch_size):
# TODO(szymon): should we ensure no repeats?
mass = random.random() * self._it_sum.sum(0, len(self._storage) - 1)
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def sample(self, batch_size, beta):
"""Sample a batch of experiences.
compared to ReplayBuffer.sample
it also returns importance weights and idxes
of sampled experiences.
Parameters
----------
batch_size: int
How many transitions to sample.
beta: float
To what degree to use importance weights
(0 - no corrections, 1 - full correction)
Returns
-------
obs_batch: np.array
batch of observations
act_batch: np.array
batch of actions executed given obs_batch
rew_batch: np.array
rewards received as results of executing act_batch
next_obs_batch: np.array
next set of observations seen after executing act_batch
done_mask: np.array
done_mask[i] = 1 if executing act_batch[i] resulted in
the end of an episode and 0 otherwise.
weights: np.array
Array of shape (batch_size,) and dtype np.float32
denoting importance weight of each sampled transition
idxes: np.array
Array of shape (batch_size,) and dtype np.int32
idexes in buffer of sampled experiences
"""
assert beta > 0
idxes = self._sample_proportional(batch_size)
weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage)) ** (-beta)
for idx in idxes:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage)) ** (-beta)
weights.append(weight / max_weight)
weights = np.array(weights)
encoded_sample = self._encode_sample(idxes)
return tuple(list(encoded_sample) + [weights, idxes])
def update_priorities(self, idxes, priorities):
"""Update priorities of sampled transitions.
sets priority of transition at index idxes[i] in buffer
to priorities[i].
Parameters
----------
idxes: [int]
List of idxes of sampled transitions
priorities: [float]
List of updated priorities corresponding to
transitions at the sampled idxes denoted by
variable `idxes`.
"""
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
assert priority > 0
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = priority ** self._alpha
self._it_min[idx] = priority ** self._alpha
self._max_priority = max(self._max_priority, priority)
class PrioritizedReplayBuffer(ReplayBuffer):
def __init__(self, size, alpha):
"""Create Prioritized Replay buffer.
Parameters
----------
size: int
Max number of transitions to store in the buffer. When the buffer
overflows the old memories are dropped.
alpha: float
how much prioritization is used
(0 - no prioritization, 1 - full prioritization)
See Also
--------
ReplayBuffer.__init__
"""
super(PrioritizedReplayBuffer, self).__init__(size)
assert alpha >= 0
self._alpha = alpha
it_capacity = 1
while it_capacity < size:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
def add(self, *args, **kwargs):
"""See ReplayBuffer.store_effect"""
idx = self._next_idx
super().add(*args, **kwargs)
self._it_sum[idx] = self._max_priority**self._alpha
self._it_min[idx] = self._max_priority**self._alpha
def _sample_proportional(self, batch_size):
res = []
for _ in range(batch_size):
# TODO(szymon): should we ensure no repeats?
mass = random.random() * self._it_sum.sum(0,
len(self._storage) - 1)
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def sample(self, batch_size, beta):
"""Sample a batch of experiences.
compared to ReplayBuffer.sample
it also returns importance weights and idxes
of sampled experiences.
Parameters
----------
batch_size: int
How many transitions to sample.
beta: float
To what degree to use importance weights
(0 - no corrections, 1 - full correction)
Returns
-------
obs_batch: np.array
batch of observations
act_batch: np.array
batch of actions executed given obs_batch
rew_batch: np.array
rewards received as results of executing act_batch
next_obs_batch: np.array
next set of observations seen after executing act_batch
done_mask: np.array
done_mask[i] = 1 if executing act_batch[i] resulted in
the end of an episode and 0 otherwise.
weights: np.array
Array of shape (batch_size,) and dtype np.float32
denoting importance weight of each sampled transition
idxes: np.array
Array of shape (batch_size,) and dtype np.int32
idexes in buffer of sampled experiences
"""
assert beta > 0
idxes = self._sample_proportional(batch_size)
weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage))**(-beta)
for idx in idxes:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage))**(-beta)
weights.append(weight / max_weight)
weights = np.array(weights)
encoded_sample = self._encode_sample(idxes)
return tuple(list(encoded_sample) + [weights, idxes])
def update_priorities(self, idxes, priorities):
"""Update priorities of sampled transitions.
sets priority of transition at index idxes[i] in buffer
to priorities[i].
Parameters
----------
idxes: [int]
List of idxes of sampled transitions
priorities: [float]
List of updated priorities corresponding to
transitions at the sampled idxes denoted by
variable `idxes`.
"""
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
assert priority > 0
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = priority**self._alpha
self._it_min[idx] = priority**self._alpha
self._max_priority = max(self._max_priority, priority)
class ReplayMemory:
def __init__(self, replay_size, alpha=0.6):
self.replay_size = replay_size
self.cnt = 0
self._alpha = alpha
it_capacity = 1
while it_capacity < replay_size:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
self._storage = []
self._maxsize = replay_size
self._next_idx = 0
def add(self, data):
#new_data = []
#for i in data:
# i.wait_to_read()
# new_data.append(copyto(i))
if self._next_idx >= len(self._storage):
self._storage.append(data)
#print self._storage
else:
self._storage[self._next_idx] = data
self._next_idx = (self._next_idx + 1) % self._maxsize
idx = self._next_idx
self._it_sum[idx] = self._max_priority ** self._alpha
self._it_min[idx] = self._max_priority ** self._alpha
def _sample_proportional(self, batch_size):
res = []
for _ in range(batch_size):
mass = random.random() * self._it_sum.sum(0, len(self._storage) - 1)
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def sample(self, batch_size, beta=0.4):
assert beta > 0
idxes = self._sample_proportional(batch_size)
weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage)) ** (-beta)
for idx in idxes:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage)) ** (-beta)
weights.append(weight / max_weight)
#print self._it_min.min(), weights
weights = np.array(weights)
weights /= np.sum(weights)
ret = []
for i in xrange(batch_size):
ret.append(self._storage[idxes[i]])
return (ret, idxes, weights)
def update_priorities(self, idxes, priorities):
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
#print priority
assert priority > 0
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = priority ** self._alpha
self._it_min[idx] = priority ** self._alpha
self._max_priority = max(self._max_priority, priority)
class PrioritizedReplayBuffer(SimpleReplayBuffer):
def __init__(self, MAX_LEN, alpha: float = 0.6):
"""
Create Prioritized Replay buffer.
Parameters
----------
size: int
Max number of transitions to store in the buffer. When the buffer
overflows the old memories are dropped.
alpha: float
how much prioritization is used
(0 - no prioritization, 1 - full prioritization)
See Also
--------
SimpleReplayBuffer.__init__
"""
super(PrioritizedReplayBuffer, self).__init__(MAX_LEN)
assert alpha >= 0
self._alpha = alpha
it_capacity = 1
while it_capacity < MAX_LEN:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
def add(self, experience: Experience):
"""See SimpleReplayBuffer.store_effect"""
idx = self._next_idx
super().add(experience)
self._it_sum[idx] = self._max_priority**self._alpha
self._it_min[idx] = self._max_priority**self._alpha
def _sample_proportional(self, batch_size: int) -> List[int]:
res = []
p_total = self._it_sum.sum(0, len(self._storage) - 1)
every_range_len = p_total / batch_size
for i in range(batch_size):
mass = random() * every_range_len + i * every_range_len
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def sample(
self,
batch_size: int,
beta: float = 0.4
) -> Tuple[List[Experience], np.ndarray, List[int]]: # type: ignore
"""Sample a batch of experiences.
compared to SimpleReplayBuffer.sample
it also returns importance weights and idxes
of sampled experiences.
Parameters
----------
batch_size: int
How many transitions to sample.
beta: float
To what degree to use importance weights
(0 - no corrections, 1 - full correction)
Returns
-------
experiences: List[Experience]
batch of experiences
weights: np.array
Array of shape (batch_size,) and dtype np.float32
denoting importance weight of each sampled transition
idxes: np.array
Array of shape (batch_size,) and dtype np.int32
idexes in buffer of sampled experiences
"""
assert beta > 0
idxes = self._sample_proportional(batch_size)
weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage))**(-beta)
for idx in idxes:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage))**(-beta)
weights.append(weight / max_weight)
weights = np.array(weights)
encoded_sample = self._encode_sample(idxes)
return (encoded_sample, weights, idxes)
def update_priorities(self, idxes, priorities):
"""Update priorities of sampled transitions.
sets priority of transition at index idxes[i] in buffer
to priorities[i].
Parameters
----------
idxes: [int]
List of idxes of sampled transitions
priorities: [float]
List of updated priorities corresponding to
transitions at the sampled idxes denoted by
variable `idxes`.
"""
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
assert priority > 0
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = priority**self._alpha
self._it_min[idx] = priority**self._alpha
self._max_priority = max(self._max_priority, priority)
class PrioritizedReplayMemory(object):
def __init__(self,
capacity=100000,
priority_fraction=0.0,
discount_gamma_game_reward=1.0,
discount_gamma_graph_reward=1.0,
discount_gamma_count_reward=1.0,
accumulate_reward_from_final=False):
# prioritized replay memory
self._storage = []
self.capacity = capacity
self._next_idx = 0
assert priority_fraction >= 0
self._alpha = priority_fraction
it_capacity = 1
while it_capacity < capacity:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
self.discount_gamma_game_reward = discount_gamma_game_reward
self.discount_gamma_graph_reward = discount_gamma_graph_reward
self.discount_gamma_count_reward = discount_gamma_count_reward
self.accumulate_reward_from_final = accumulate_reward_from_final
def __len__(self):
return len(self._storage)
@property
def storage(self):
"""[(np.ndarray, float, float, np.ndarray, bool)]: content of the replay buffer"""
return self._storage
@property
def buffer_size(self):
"""float: Max capacity of the buffer"""
return self.capacity
def can_sample(self, n_samples):
"""
Check if n_samples samples can be sampled
from the buffer.
:param n_samples: (int)
:return: (bool)
"""
return len(self) >= n_samples
def is_full(self):
"""
Check whether the replay buffer is full or not.
:return: (bool)
"""
return len(self) == self.buffer_size
def add(self, *args):
"""
add a new transition to the buffer
"""
idx = self._next_idx
data = Transition(*args)
if self._next_idx >= len(self._storage):
self._storage.append(data)
else:
self._storage[self._next_idx] = data
self._next_idx = (self._next_idx + 1) % self.capacity
self._it_sum[idx] = self._max_priority**self._alpha
self._it_min[idx] = self._max_priority**self._alpha
def get_next_final_pos(self, which_memory, head):
i = head
while True:
if i >= len(self._storage):
return None
if self._storage[i].is_final:
return i
i += 1
return None
def _get_single_transition(self, idx, n):
assert n > 0
head = idx
# if n is 1, then head can't be is_final
if n == 1:
if self._storage[head].is_final:
return None
# if n > 1, then all except tail can't be is_final
else:
if np.any([item.is_final
for item in self._storage[head:head + n]]):
return None
next_final = self.get_next_final_pos(self._storage, head)
if next_final is None:
return None
# all good
obs = self._storage[head].observation_list
candidate = self._storage[head].action_candidate_list
chosen_indices = self._storage[head].chosen_indices
graph_triplets = self._storage[head].graph_triplets
next_obs = self._storage[head + n].observation_list
next_candidate = self._storage[head + n].action_candidate_list
next_graph_triplets = self._storage[head + n].graph_triplets
tmp = next_final - head + 1 if self.accumulate_reward_from_final else n + 1
rewards_up_to_next_final = [
self.discount_gamma_game_reward**i * self._storage[head + i].reward
for i in range(tmp)
]
reward = torch.sum(torch.stack(rewards_up_to_next_final))
graph_rewards_up_to_next_final = [
self.discount_gamma_graph_reward**i *
self._storage[head + i].graph_reward for i in range(tmp)
]
graph_reward = torch.sum(torch.stack(graph_rewards_up_to_next_final))
count_rewards_up_to_next_final = [
self.discount_gamma_count_reward**i *
self._storage[head + i].count_reward for i in range(tmp)
]
count_reward = torch.sum(torch.stack(count_rewards_up_to_next_final))
return (obs, candidate, chosen_indices, graph_triplets,
reward + graph_reward + count_reward, next_obs, next_candidate,
next_graph_triplets)
def _encode_sample(self, idxes, ns):
actual_indices, actual_ns = [], []
obs, candidate, chosen_indices, graph_triplets, reward, next_obs, next_candidate, next_graph_triplets = [], [], [], [], [], [], [], []
for i, n in zip(idxes, ns):
t = self._get_single_transition(i, n)
if t is None:
continue
actual_indices.append(i)
actual_ns.append(n)
obs.append(t[0])
candidate.append(t[1])
chosen_indices.append(t[2])
graph_triplets.append(t[3])
reward.append(t[4])
next_obs.append(t[5])
next_candidate.append(t[6])
next_graph_triplets.append(t[7])
if len(actual_indices) == 0:
return None
chosen_indices = np.array(chosen_indices) # batch
reward = torch.stack(reward, 0) # batch
actual_ns = np.array(actual_ns)
return [
obs, candidate, chosen_indices, graph_triplets, reward, next_obs,
next_candidate, next_graph_triplets, actual_indices, actual_ns
]
def sample(self, batch_size, beta=0, multi_step=1):
assert beta > 0
idxes = self._sample_proportional(batch_size)
weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage))**(-beta)
# sample n
ns = np.random.randint(1, multi_step + 1, size=batch_size)
encoded_sample = self._encode_sample(idxes, ns)
if encoded_sample is None:
return None
actual_indices = encoded_sample[-2]
for idx in actual_indices:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage))**(-beta)
weights.append(weight / max_weight)
weights = np.array(weights)
return encoded_sample + [weights]
def _get_single_sequence_transition(self, idx, sample_history_length):
assert sample_history_length > 0
head = idx
# if n is 1, then head can't be is_final
if sample_history_length == 1:
if self._storage[head].is_final:
return None
# if n > 1, then all except tail can't be is_final
else:
if np.any([
item.is_final
for item in self._storage[head:head +
sample_history_length]
]):
return None
next_final = self.get_next_final_pos(self._storage, head)
if next_final is None:
return None
# all good
res = []
for m in range(sample_history_length):
obs = self._storage[head + m].observation_list
candidate = self._storage[head + m].action_candidate_list
chosen_indices = self._storage[head + m].chosen_indices
graph_triplets = self._storage[head + m].graph_triplets
next_obs = self._storage[head + m + 1].observation_list
next_candidate = self._storage[head + m + 1].action_candidate_list
next_graph_triplets = self._storage[head + m + 1].graph_triplets
tmp = next_final - (
head + m) + 1 if self.accumulate_reward_from_final else 1
rewards_up_to_next_final = [
self.discount_gamma_game_reward**i *
self._storage[head + m + i].reward for i in range(tmp)
]
reward = torch.sum(torch.stack(rewards_up_to_next_final))
graph_rewards_up_to_next_final = [
self.discount_gamma_graph_reward**i *
self._storage[head + m + i].graph_reward for i in range(tmp)
]
graph_reward = torch.sum(
torch.stack(graph_rewards_up_to_next_final))
count_rewards_up_to_next_final = [
self.discount_gamma_count_reward**i *
self._storage[head + m + i].count_reward for i in range(tmp)
]
count_reward = torch.sum(
torch.stack(count_rewards_up_to_next_final))
res.append([
obs, candidate, chosen_indices, graph_triplets,
reward + graph_reward + count_reward, next_obs, next_candidate,
next_graph_triplets
])
return res
def _encode_sample_sequence(self, idxes, sample_history_length):
assert sample_history_length > 0
res = []
for _ in range(sample_history_length):
tmp = []
for i in range(8):
tmp.append([])
res.append(tmp)
actual_indices = []
# obs, candidate, chosen_indices, graph_triplets, reward, next_obs, next_candidate, next_graph_triplets
for i in idxes:
t = self._get_single_sequence_transition(i, sample_history_length)
if t is None:
continue
actual_indices.append(i)
for step in range(sample_history_length):
t_s = t[step]
res[step][0].append(t_s[0])
res[step][1].append(t_s[1])
res[step][2].append(t_s[2])
res[step][3].append(t_s[3])
res[step][4].append(t_s[4])
res[step][5].append(t_s[5])
res[step][6].append(t_s[6])
res[step][7].append(t_s[7])
if len(actual_indices) == 0:
return None
for i in range(sample_history_length):
res[i][2] = np.array(res[i][2]) # batch
res[i][4] = torch.stack(res[i][4], 0) # batch
return res + [actual_indices]
def sample_sequence(self, batch_size, beta=0, sample_history_length=1):
assert beta > 0
idxes = self._sample_proportional(batch_size)
res_weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage))**(-beta)
encoded_sample = self._encode_sample_sequence(idxes,
sample_history_length)
if encoded_sample is None:
return None
actual_indices = encoded_sample[-1]
for _h in range(sample_history_length):
tmp_weights = []
for idx in actual_indices:
p_sample = self._it_sum[idx + _h] / self._it_sum.sum()
weight = (p_sample * len(self._storage))**(-beta)
tmp_weights.append(weight / max_weight)
tmp_weights = np.array(tmp_weights)
res_weights.append(tmp_weights)
return encoded_sample + [res_weights]
def _sample_proportional(self, batch_size):
res = []
for _ in range(batch_size):
mass = random.random() * self._it_sum.sum(0,
len(self._storage) - 1)
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def update_priorities(self, idxes, priorities):
"""
Update priorities of sampled transitions.
sets priority of transition at index idxes[i] in buffer
to priorities[i].
:param idxes: ([int]) List of idxes of sampled transitions
:param priorities: ([float]) List of updated priorities corresponding to transitions at the sampled idxes
denoted by variable `idxes`.
"""
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
assert priority > 0
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = priority**self._alpha
self._it_min[idx] = priority**self._alpha
self._max_priority = max(self._max_priority, priority)
def avg_rewards(self):
if len(self._storage) == 0:
return 0.0
rewards = [self._storage[i].reward for i in range(len(self._storage))]
return to_np(torch.mean(torch.stack(rewards)))
class PrioritizedReplayMemory:
def __init__(self, size, alpha=0.6, beta_start=0.4, beta_frames=100000):
super(PrioritizedReplayMemory, self).__init__()
self._storage = []
self._maxsize = size
self._next_idx = 0
assert alpha >= 0
self._alpha = alpha
self.beta_start = beta_start
self.beta_frames = beta_frames
self.frame = 1
it_capacity = 1
while it_capacity < size:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
self.experience = namedtuple(
"Experience",
field_names=["state", "action", "reward", "next_state", "done"])
def beta_by_frame(self, frame_idx):
return min(
1.0, self.beta_start + frame_idx *
(1.0 - self.beta_start) / self.beta_frames)
def push(self, state, action, reward, next_state, done):
idx = self._next_idx
if self._next_idx >= len(self._storage):
self._storage.append(
self.experience(state, action, reward, next_state, done))
else:
self._storage[self._next_idx] = self.experience(
state, action, reward, next_state, done)
self._next_idx = (self._next_idx + 1) % self._maxsize
self._it_sum[idx] = self._max_priority**self._alpha
self._it_min[idx] = self._max_priority**self._alpha
def _encode_sample(self, idxes):
states = torch.from_numpy(
np.vstack([self._storage[i].state
for i in idxes])).float().to(device)
actions = torch.from_numpy(
np.vstack([self._storage[i].action
for i in idxes])).float().to(device)
rewards = torch.from_numpy(
np.vstack([self._storage[i].reward
for i in idxes])).float().to(device)
next_states = torch.from_numpy(
np.vstack([self._storage[i].next_state
for i in idxes])).float().to(device)
dones = torch.from_numpy(
np.vstack([self._storage[i].done
for i in idxes]).astype(np.uint8)).float().to(device)
return (states, actions, rewards, next_states, dones)
def _sample_proportional(self, batch_size):
res = []
for _ in range(batch_size):
mass = random.random() * self._it_sum.sum(0,
len(self._storage) - 1)
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def sample(self, batch_size):
idxes = self._sample_proportional(batch_size)
weights = []
#find smallest sampling prob: p_min = smallest priority^alpha / sum of priorities^alpha
p_min = self._it_min.min() / self._it_sum.sum()
beta = self.beta_by_frame(self.frame)
self.frame += 1
#max_weight given to smallest prob
max_weight = (p_min * len(self._storage))**(-beta)
for idx in idxes:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage))**(-beta)
weights.append(weight / max_weight)
weights = torch.tensor(weights, device=device, dtype=torch.float)
encoded_sample = self._encode_sample(idxes)
return encoded_sample, idxes, weights
def update_priorities(self, idxes, priorities):
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = (priority + 1e-5)**self._alpha
self._it_min[idx] = (priority + 1e-5)**self._alpha
self._max_priority = max(self._max_priority, (priority + 1e-5))
class PrioritizedReplayBuffer(ReplayBuffer):
def __init__(self, size, alpha):
"""Create Prioritized Replay buffer.
Parameters
----------
size: int
Max number of transitions to store in the buffer. When the buffer
overflows the old memories are dropped.
alpha: float
how much prioritization is used
(0 - no prioritization, 1 - full prioritization)
See Also
--------
ReplayBuffer.__init__
"""
super(PrioritizedReplayBuffer, self).__init__(size)
assert alpha > 0
self._alpha = alpha
it_capacity = 1
while it_capacity < size:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
def add(self, *args, **kwargs):
"""See ReplayBuffer.store_effect"""
idx = self._next_idx
super().add(*args, **kwargs)
self._it_sum[idx] = self._max_priority**self._alpha
self._it_min[idx] = self._max_priority**self._alpha
def _sample_proportional(self, batch_size):
res = []
for _ in range(batch_size):
# TODO(szymon): should we ensure no repeats?
mass = random.random() * self._it_sum.sum(0,
len(self._storage) - 1)
idx = self._it_sum.find_prefixsum_idx(mass)
res.append(idx)
return res
def sample(self, batch_size, beta):
assert beta > 0
idxes = self._sample_proportional(batch_size)
weights = []
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self._storage))**(-beta)
for idx in idxes:
p_sample = self._it_sum[idx] / self._it_sum.sum()
weight = (p_sample * len(self._storage))**(-beta)
weights.append(weight / max_weight)
weights = np.array(weights)
encoded_sample = self._encode_sample(idxes)
return tuple(list(encoded_sample) + [weights, idxes])
def update_priorities(self, idxes, priorities):
"""Update priorities of sampled transitions.
sets priority of transition at index idxes[i] in buffer
to priorities[i].
Parameters
----------
idxes: [int]
List of idxes of sampled transitions
priorities: [float]
List of updated priorities corresponding to
transitions at the sampled idxes denoted by
variable `idxes`.
"""
assert len(idxes) == len(priorities)
for idx, priority in zip(idxes, priorities):
assert priority > 0
assert 0 <= idx < len(self._storage)
self._it_sum[idx] = priority**self._alpha
self._it_min[idx] = priority**self._alpha
self._max_priority = max(self._max_priority, priority)
class PrioritizedReplayBuffer(ReplayBuffer):
"""
Adapt from https://github.com/hill-a/stable-baselines/blob/master/stable_baselines/common/buffers.py
"""
def __init__(self, obs_space, action_space, capacity, exponent, device, optimize_memory_usage=False):
super().__init__(obs_space, action_space, capacity, device,
optimize_memory_usage=optimize_memory_usage)
assert exponent >= 0
self.exponent = exponent
it_capacity = 1
while it_capacity < self.capacity:
it_capacity *= 2
self._it_sum = SumSegmentTree(it_capacity)
self._it_min = MinSegmentTree(it_capacity)
self._max_priority = 1.0
def _sample_proportional(self, batch_size):
total = self._it_sum.sum(0, len(self) - 1)
mass = np.random.random(size=batch_size) * total
idx = self._it_sum.find_prefixsum_idx(mass)
# replace idx == self.idx
if self.full and self.optimize_memory_usage:
while np.any(idx == self.idx):
replace_mass = np.random.random(len(idx == self.idx)) * total
replace_idx = self._it_sum.find_prefixsum_idx(replace_mass)
idx[idx == self.idx] = replace_idx
return idx
def add(self, obs, action, reward, next_obs, done):
idx = self.idx
super().add(obs, action, reward, next_obs, done)
self._it_sum[idx] = self._max_priority ** self.exponent
self._it_min[idx] = self._max_priority ** self.exponent
def sample(self, batch_size, beta=0):
assert beta >= 0
idxes = self._sample_proportional(batch_size)
p_min = self._it_min.min() / self._it_sum.sum()
max_weight = (p_min * len(self)) ** (-beta)
p_sample = self._it_sum[idxes] / self._it_sum.sum()
weights = (p_sample * len(self)) ** (-beta) / max_weight
obses, actions, rewards, next_obses, not_dones = self._sample(idxes)
priority_kwargs = {
'weights': weights,
'idxes': idxes
}
return obses, actions, rewards, next_obses, not_dones, priority_kwargs
def update_priorities(self, idxes, priorities):
assert len(idxes) == len(priorities)
assert np.min(priorities) > 0
assert np.min(idxes) >= 0
assert np.max(idxes) < len(self)
self._it_sum[idxes] = priorities ** self.exponent
self._it_min[idxes] = priorities ** self.exponent
self._max_priority = max(self._max_priority, np.max(priorities))