-
Notifications
You must be signed in to change notification settings - Fork 0
/
distributed.py
254 lines (213 loc) · 8.43 KB
/
distributed.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
import math
import pickle
import torch
import torch.utils.data as data
import torch.distributed as dist
from torch.utils.data.sampler import Sampler, BatchSampler
__all__ = ['get_world_size', 'get_rank', 'synchronize', 'is_main_process',
'all_gather', 'make_data_sampler', 'make_batch_data_sampler',
'reduce_dict', 'reduce_loss_dict']
# reference: https://github.com/facebookresearch/maskrcnn-benchmark/blob/master/maskrcnn_benchmark/utils/comm.py
def get_world_size():
if not dist.is_available():
return 1
if not dist.is_initialized():
return 1
return dist.get_world_size()
def get_rank():
if not dist.is_available():
return 0
if not dist.is_initialized():
return 0
return dist.get_rank()
def is_main_process():
return get_rank() == 0
def synchronize():
"""
Helper function to synchronize (barrier) among all processes when
using distributed training
"""
if not dist.is_available():
return
if not dist.is_initialized():
return
world_size = dist.get_world_size()
if world_size == 1:
return
dist.barrier()
def all_gather(data):
"""
Run all_gather on arbitrary picklable data (not necessarily tensors)
Args:
data: any picklable object
Returns:
list[data]: list of data gathered from each rank
"""
world_size = get_world_size()
if world_size == 1:
return [data]
# serialized to a Tensor
buffer = pickle.dumps(data)
storage = torch.ByteStorage.from_buffer(buffer)
tensor = torch.ByteTensor(storage).to("cuda")
# obtain Tensor size of each rank
local_size = torch.IntTensor([tensor.numel()]).to("cuda")
size_list = [torch.IntTensor([0]).to("cuda") for _ in range(world_size)]
dist.all_gather(size_list, local_size)
size_list = [int(size.item()) for size in size_list]
max_size = max(size_list)
# receiving Tensor from all ranks
# we pad the tensor because torch all_gather does not support
# gathering tensors of different shapes
tensor_list = []
for _ in size_list:
tensor_list.append(torch.ByteTensor(size=(max_size,)).to("cuda"))
if local_size != max_size:
padding = torch.ByteTensor(size=(max_size - local_size,)).to("cuda")
tensor = torch.cat((tensor, padding), dim=0)
dist.all_gather(tensor_list, tensor)
data_list = []
for size, tensor in zip(size_list, tensor_list):
buffer = tensor.cpu().numpy().tobytes()[:size]
data_list.append(pickle.loads(buffer))
return data_list
def reduce_dict(input_dict, average=True):
"""
Args:
input_dict (dict): all the values will be reduced
average (bool): whether to do average or sum
Reduce the values in the dictionary from all processes so that process with rank
0 has the averaged results. Returns a dict with the same fields as
input_dict, after reduction.
"""
world_size = get_world_size()
if world_size < 2:
return input_dict
with torch.no_grad():
names = []
values = []
# sort the keys so that they are consistent across processes
for k in sorted(input_dict.keys()):
names.append(k)
values.append(input_dict[k])
values = torch.stack(values, dim=0)
dist.reduce(values, dst=0)
if dist.get_rank() == 0 and average:
# only main process gets accumulated, so only divide by
# world_size in this case
values /= world_size
reduced_dict = {k: v for k, v in zip(names, values)}
return reduced_dict
def reduce_loss_dict(loss_dict):
"""
Reduce the loss dictionary from all processes so that process with rank
0 has the averaged results. Returns a dict with the same fields as
loss_dict, after reduction.
"""
world_size = get_world_size()
if world_size < 2:
return loss_dict
with torch.no_grad():
loss_names = []
all_losses = []
for k in sorted(loss_dict.keys()):
loss_names.append(k)
all_losses.append(loss_dict[k])
all_losses = torch.stack(all_losses, dim=0)
dist.reduce(all_losses, dst=0)
if dist.get_rank() == 0:
# only main process gets accumulated, so only divide by
# world_size in this case
all_losses /= world_size
reduced_losses = {k: v for k, v in zip(loss_names, all_losses)}
return reduced_losses
def make_data_sampler(dataset, shuffle, distributed):
if distributed:
return DistributedSampler(dataset, shuffle=shuffle)
if shuffle:
sampler = data.sampler.RandomSampler(dataset)
else:
sampler = data.sampler.SequentialSampler(dataset)
return sampler
def make_batch_data_sampler(sampler, images_per_batch, num_iters=None, start_iter=0):
batch_sampler = data.sampler.BatchSampler(sampler, images_per_batch, drop_last=True)
if num_iters is not None:
batch_sampler = IterationBasedBatchSampler(batch_sampler, num_iters, start_iter)
return batch_sampler
# Code is copy-pasted from https://github.com/facebookresearch/maskrcnn-benchmark/blob/master/maskrcnn_benchmark/data/samplers/distributed.py
class DistributedSampler(Sampler):
"""Sampler that restricts data loading to a subset of the dataset.
It is especially useful in conjunction with
:class:`torch.nn.parallel.DistributedDataParallel`. In such case, each
process can pass a DistributedSampler instance as a DataLoader sampler,
and load a subset of the original dataset that is exclusive to it.
.. note::
Dataset is assumed to be of constant size.
Arguments:
dataset: Dataset used for sampling.
num_replicas (optional): Number of processes participating in
distributed training.
rank (optional): Rank of the current process within num_replicas.
"""
def __init__(self, dataset, num_replicas=None, rank=None, shuffle=True):
if num_replicas is None:
if not dist.is_available():
raise RuntimeError("Requires distributed package to be available")
num_replicas = dist.get_world_size()
if rank is None:
if not dist.is_available():
raise RuntimeError("Requires distributed package to be available")
rank = dist.get_rank()
self.dataset = dataset
self.num_replicas = num_replicas
self.rank = rank
self.epoch = 0
self.num_samples = int(math.ceil(len(self.dataset) * 1.0 / self.num_replicas))
self.total_size = self.num_samples * self.num_replicas
self.shuffle = shuffle
def __iter__(self):
if self.shuffle:
# deterministically shuffle based on epoch
g = torch.Generator()
g.manual_seed(self.epoch)
indices = torch.randperm(len(self.dataset), generator=g).tolist()
else:
indices = torch.arange(len(self.dataset)).tolist()
# add extra samples to make it evenly divisible
indices += indices[: (self.total_size - len(indices))]
assert len(indices) == self.total_size
# subsample
offset = self.num_samples * self.rank
indices = indices[offset: offset + self.num_samples]
assert len(indices) == self.num_samples
return iter(indices)
def __len__(self):
return self.num_samples
def set_epoch(self, epoch):
self.epoch = epoch
class IterationBasedBatchSampler(BatchSampler):
"""
Wraps a BatchSampler, resampling from it until
a specified number of iterations have been sampled
"""
def __init__(self, batch_sampler, num_iterations, start_iter=0):
self.batch_sampler = batch_sampler
self.num_iterations = num_iterations
self.start_iter = start_iter
def __iter__(self):
iteration = self.start_iter
while iteration <= self.num_iterations:
# if the underlying sampler has a set_epoch method, like
# DistributedSampler, used for making each process see
# a different split of the dataset, then set it
if hasattr(self.batch_sampler.sampler, "set_epoch"):
self.batch_sampler.sampler.set_epoch(iteration)
for batch in self.batch_sampler:
iteration += 1
if iteration > self.num_iterations:
break
yield batch
def __len__(self):
return self.num_iterations
if __name__ == '__main__':
pass