File size: 12,973 Bytes
8f6558d
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
# -*- coding: utf-8 -*-
# File   : batchnorm.py
# Author : Jiayuan Mao
# Email  : [email protected]
# Date   : 27/01/2018
# 
# This file is part of Synchronized-BatchNorm-PyTorch.
# https://github.com/vacancy/Synchronized-BatchNorm-PyTorch
# Distributed under MIT License.

import collections

import torch
import torch.nn.functional as F

from torch.nn.modules.batchnorm import _BatchNorm
from torch.nn.parallel._functions import ReduceAddCoalesced, Broadcast

from .comm import SyncMaster

__all__ = ['SynchronizedBatchNorm1d', 'SynchronizedBatchNorm2d', 'SynchronizedBatchNorm3d']


def _sum_ft(tensor):
    """sum over the first and last dimention"""
    return tensor.sum(dim=0).sum(dim=-1)


def _unsqueeze_ft(tensor):
    """add new dementions at the front and the tail"""
    return tensor.unsqueeze(0).unsqueeze(-1)


_ChildMessage = collections.namedtuple('_ChildMessage', ['sum', 'ssum', 'sum_size'])
_MasterMessage = collections.namedtuple('_MasterMessage', ['sum', 'inv_std'])


class _SynchronizedBatchNorm(_BatchNorm):
    def __init__(self, num_features, eps=1e-5, momentum=0.1, affine=True):
        super(_SynchronizedBatchNorm, self).__init__(num_features, eps=eps, momentum=momentum, affine=affine)

        self._sync_master = SyncMaster(self._data_parallel_master)

        self._is_parallel = False
        self._parallel_id = None
        self._slave_pipe = None

    def forward(self, input):
        # If it is not parallel computation or is in evaluation mode, use PyTorch's implementation.
        if not (self._is_parallel and self.training):
            return F.batch_norm(
                input, self.running_mean, self.running_var, self.weight, self.bias,
                self.training, self.momentum, self.eps)

        # Resize the input to (B, C, -1).
        input_shape = input.size()
        input = input.view(input.size(0), self.num_features, -1)

        # Compute the sum and square-sum.
        sum_size = input.size(0) * input.size(2)
        input_sum = _sum_ft(input)
        input_ssum = _sum_ft(input ** 2)

        # Reduce-and-broadcast the statistics.
        if self._parallel_id == 0:
            mean, inv_std = self._sync_master.run_master(_ChildMessage(input_sum, input_ssum, sum_size))
        else:
            mean, inv_std = self._slave_pipe.run_slave(_ChildMessage(input_sum, input_ssum, sum_size))

        # Compute the output.
        if self.affine:
            # MJY:: Fuse the multiplication for speed.
            output = (input - _unsqueeze_ft(mean)) * _unsqueeze_ft(inv_std * self.weight) + _unsqueeze_ft(self.bias)
        else:
            output = (input - _unsqueeze_ft(mean)) * _unsqueeze_ft(inv_std)

        # Reshape it.
        return output.view(input_shape)

    def __data_parallel_replicate__(self, ctx, copy_id):
        self._is_parallel = True
        self._parallel_id = copy_id

        # parallel_id == 0 means master device.
        if self._parallel_id == 0:
            ctx.sync_master = self._sync_master
        else:
            self._slave_pipe = ctx.sync_master.register_slave(copy_id)

    def _data_parallel_master(self, intermediates):
        """Reduce the sum and square-sum, compute the statistics, and broadcast it."""

        # Always using same "device order" makes the ReduceAdd operation faster.
        # Thanks to:: Tete Xiao (http://tetexiao.com/)
        intermediates = sorted(intermediates, key=lambda i: i[1].sum.get_device())

        to_reduce = [i[1][:2] for i in intermediates]
        to_reduce = [j for i in to_reduce for j in i]  # flatten
        target_gpus = [i[1].sum.get_device() for i in intermediates]

        sum_size = sum([i[1].sum_size for i in intermediates])
        sum_, ssum = ReduceAddCoalesced.apply(target_gpus[0], 2, *to_reduce)
        mean, inv_std = self._compute_mean_std(sum_, ssum, sum_size)

        broadcasted = Broadcast.apply(target_gpus, mean, inv_std)

        outputs = []
        for i, rec in enumerate(intermediates):
            outputs.append((rec[0], _MasterMessage(*broadcasted[i*2:i*2+2])))

        return outputs

    def _compute_mean_std(self, sum_, ssum, size):
        """Compute the mean and standard-deviation with sum and square-sum. This method
        also maintains the moving average on the master device."""
        assert size > 1, 'BatchNorm computes unbiased standard-deviation, which requires size > 1.'
        mean = sum_ / size
        sumvar = ssum - sum_ * mean
        unbias_var = sumvar / (size - 1)
        bias_var = sumvar / size

        self.running_mean = (1 - self.momentum) * self.running_mean + self.momentum * mean.data
        self.running_var = (1 - self.momentum) * self.running_var + self.momentum * unbias_var.data

        return mean, bias_var.clamp(self.eps) ** -0.5


class SynchronizedBatchNorm1d(_SynchronizedBatchNorm):
    r"""Applies Synchronized Batch Normalization over a 2d or 3d input that is seen as a
    mini-batch.

    .. math::

        y = \frac{x - mean[x]}{ \sqrt{Var[x] + \epsilon}} * gamma + beta

    This module differs from the built-in PyTorch BatchNorm1d as the mean and
    standard-deviation are reduced across all devices during training.

    For example, when one uses `nn.DataParallel` to wrap the network during
    training, PyTorch's implementation normalize the tensor on each device using
    the statistics only on that device, which accelerated the computation and
    is also easy to implement, but the statistics might be inaccurate.
    Instead, in this synchronized version, the statistics will be computed
    over all training samples distributed on multiple devices.
    
    Note that, for one-GPU or CPU-only case, this module behaves exactly same
    as the built-in PyTorch implementation.

    The mean and standard-deviation are calculated per-dimension over
    the mini-batches and gamma and beta are learnable parameter vectors
    of size C (where C is the input size).

    During training, this layer keeps a running estimate of its computed mean
    and variance. The running sum is kept with a default momentum of 0.1.

    During evaluation, this running mean/variance is used for normalization.

    Because the BatchNorm is done over the `C` dimension, computing statistics
    on `(N, L)` slices, it's common terminology to call this Temporal BatchNorm

    Args:
        num_features: num_features from an expected input of size
            `batch_size x num_features [x width]`
        eps: a value added to the denominator for numerical stability.
            Default: 1e-5
        momentum: the value used for the running_mean and running_var
            computation. Default: 0.1
        affine: a boolean value that when set to ``True``, gives the layer learnable
            affine parameters. Default: ``True``

    Shape:
        - Input: :math:`(N, C)` or :math:`(N, C, L)`
        - Output: :math:`(N, C)` or :math:`(N, C, L)` (same shape as input)

    Examples:
        >>> # With Learnable Parameters
        >>> m = SynchronizedBatchNorm1d(100)
        >>> # Without Learnable Parameters
        >>> m = SynchronizedBatchNorm1d(100, affine=False)
        >>> input = torch.autograd.Variable(torch.randn(20, 100))
        >>> output = m(input)
    """

    def _check_input_dim(self, input):
        if input.dim() != 2 and input.dim() != 3:
            raise ValueError('expected 2D or 3D input (got {}D input)'
                             .format(input.dim()))
        super(SynchronizedBatchNorm1d, self)._check_input_dim(input)


class SynchronizedBatchNorm2d(_SynchronizedBatchNorm):
    r"""Applies Batch Normalization over a 4d input that is seen as a mini-batch
    of 3d inputs

    .. math::

        y = \frac{x - mean[x]}{ \sqrt{Var[x] + \epsilon}} * gamma + beta

    This module differs from the built-in PyTorch BatchNorm2d as the mean and
    standard-deviation are reduced across all devices during training.

    For example, when one uses `nn.DataParallel` to wrap the network during
    training, PyTorch's implementation normalize the tensor on each device using
    the statistics only on that device, which accelerated the computation and
    is also easy to implement, but the statistics might be inaccurate.
    Instead, in this synchronized version, the statistics will be computed
    over all training samples distributed on multiple devices.
    
    Note that, for one-GPU or CPU-only case, this module behaves exactly same
    as the built-in PyTorch implementation.

    The mean and standard-deviation are calculated per-dimension over
    the mini-batches and gamma and beta are learnable parameter vectors
    of size C (where C is the input size).

    During training, this layer keeps a running estimate of its computed mean
    and variance. The running sum is kept with a default momentum of 0.1.

    During evaluation, this running mean/variance is used for normalization.

    Because the BatchNorm is done over the `C` dimension, computing statistics
    on `(N, H, W)` slices, it's common terminology to call this Spatial BatchNorm

    Args:
        num_features: num_features from an expected input of
            size batch_size x num_features x height x width
        eps: a value added to the denominator for numerical stability.
            Default: 1e-5
        momentum: the value used for the running_mean and running_var
            computation. Default: 0.1
        affine: a boolean value that when set to ``True``, gives the layer learnable
            affine parameters. Default: ``True``

    Shape:
        - Input: :math:`(N, C, H, W)`
        - Output: :math:`(N, C, H, W)` (same shape as input)

    Examples:
        >>> # With Learnable Parameters
        >>> m = SynchronizedBatchNorm2d(100)
        >>> # Without Learnable Parameters
        >>> m = SynchronizedBatchNorm2d(100, affine=False)
        >>> input = torch.autograd.Variable(torch.randn(20, 100, 35, 45))
        >>> output = m(input)
    """

    def _check_input_dim(self, input):
        if input.dim() != 4:
            raise ValueError('expected 4D input (got {}D input)'
                             .format(input.dim()))
        super(SynchronizedBatchNorm2d, self)._check_input_dim(input)


class SynchronizedBatchNorm3d(_SynchronizedBatchNorm):
    r"""Applies Batch Normalization over a 5d input that is seen as a mini-batch
    of 4d inputs

    .. math::

        y = \frac{x - mean[x]}{ \sqrt{Var[x] + \epsilon}} * gamma + beta

    This module differs from the built-in PyTorch BatchNorm3d as the mean and
    standard-deviation are reduced across all devices during training.

    For example, when one uses `nn.DataParallel` to wrap the network during
    training, PyTorch's implementation normalize the tensor on each device using
    the statistics only on that device, which accelerated the computation and
    is also easy to implement, but the statistics might be inaccurate.
    Instead, in this synchronized version, the statistics will be computed
    over all training samples distributed on multiple devices.
    
    Note that, for one-GPU or CPU-only case, this module behaves exactly same
    as the built-in PyTorch implementation.

    The mean and standard-deviation are calculated per-dimension over
    the mini-batches and gamma and beta are learnable parameter vectors
    of size C (where C is the input size).

    During training, this layer keeps a running estimate of its computed mean
    and variance. The running sum is kept with a default momentum of 0.1.

    During evaluation, this running mean/variance is used for normalization.

    Because the BatchNorm is done over the `C` dimension, computing statistics
    on `(N, D, H, W)` slices, it's common terminology to call this Volumetric BatchNorm
    or Spatio-temporal BatchNorm

    Args:
        num_features: num_features from an expected input of
            size batch_size x num_features x depth x height x width
        eps: a value added to the denominator for numerical stability.
            Default: 1e-5
        momentum: the value used for the running_mean and running_var
            computation. Default: 0.1
        affine: a boolean value that when set to ``True``, gives the layer learnable
            affine parameters. Default: ``True``

    Shape:
        - Input: :math:`(N, C, D, H, W)`
        - Output: :math:`(N, C, D, H, W)` (same shape as input)

    Examples:
        >>> # With Learnable Parameters
        >>> m = SynchronizedBatchNorm3d(100)
        >>> # Without Learnable Parameters
        >>> m = SynchronizedBatchNorm3d(100, affine=False)
        >>> input = torch.autograd.Variable(torch.randn(20, 100, 35, 45, 10))
        >>> output = m(input)
    """

    def _check_input_dim(self, input):
        if input.dim() != 5:
            raise ValueError('expected 5D input (got {}D input)'
                             .format(input.dim()))
        super(SynchronizedBatchNorm3d, self)._check_input_dim(input)