forked from PaddlePaddle/PaddleSeg
-
Notifications
You must be signed in to change notification settings - Fork 0
/
binary_cross_entropy_loss.py
175 lines (165 loc) · 8.16 KB
/
binary_cross_entropy_loss.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
# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import paddle
import paddle.nn as nn
import paddle.nn.functional as F
from paddleseg.cvlibs import manager
@manager.LOSSES.add_component
class BCELoss(nn.Layer):
r"""
This operator combines the sigmoid layer and the :ref:`api_nn_loss_BCELoss` layer.
Also, we can see it as the combine of ``sigmoid_cross_entropy_with_logits``
layer and some reduce operations.
This measures the element-wise probability error in classification tasks
in which each class is independent.
This can be thought of as predicting labels for a data-point, where labels
are not mutually exclusive. For example, a news article can be about
politics, technology or sports at the same time or none of these.
First this operator calculate loss function as follows:
.. math::
Out = -Labels * \\log(\\sigma(Logit)) - (1 - Labels) * \\log(1 - \\sigma(Logit))
We know that :math:`\\sigma(Logit) = \\frac{1}{1 + \\e^{-Logit}}`. By substituting this we get:
.. math::
Out = Logit - Logit * Labels + \\log(1 + \\e^{-Logit})
For stability and to prevent overflow of :math:`\\e^{-Logit}` when Logit < 0,
we reformulate the loss as follows:
.. math::
Out = \\max(Logit, 0) - Logit * Labels + \\log(1 + \\e^{-\|Logit\|})
Then, if ``weight`` or ``pos_weight`` is not None, this operator multiply the
weight tensor on the loss `Out`. The ``weight`` tensor will attach different
weight on every items in the batch. The ``pos_weight`` will attach different
weight on the positive label of each class.
Finally, this operator applies reduce operation on the loss.
If :attr:`reduction` set to ``'none'``, the operator will return the original loss `Out`.
If :attr:`reduction` set to ``'mean'``, the reduced mean loss is :math:`Out = MEAN(Out)`.
If :attr:`reduction` set to ``'sum'``, the reduced sum loss is :math:`Out = SUM(Out)`.
Note that the target labels ``label`` should be numbers between 0 and 1.
Args:
weight (Tensor | str, optional): A manual rescaling weight given to the loss of each
batch element. If given, it has to be a 1D Tensor whose size is `[N, ]`,
The data type is float32, float64. If type is str, it should equal to 'dynamic'.
It will compute weight dynamically in every step.
Default is ``'None'``.
pos_weight (float|str, optional): A weight of positive examples. If type is str,
it should equal to 'dynamic'. It will compute weight dynamically in every step.
Default is ``'None'``.
ignore_index (int64, optional): Specifies a target value that is ignored
and does not contribute to the input gradient. Default ``255``.
edge_label (bool, optional): Whether to use edge label. Default: False
Shapes:
logit (Tensor): The input predications tensor. 2-D tensor with shape: [N, *],
N is batch_size, `*` means number of additional dimensions. The ``logit``
is usually the output of Linear layer. Available dtype is float32, float64.
label (Tensor): The target labels tensor. 2-D tensor with the same shape as
``logit``. The target labels which values should be numbers between 0 and 1.
Available dtype is float32, float64.
Returns:
A callable object of BCEWithLogitsLoss.
Examples:
.. code-block:: python
import paddle
paddle.disable_static()
logit = paddle.to_tensor([5.0, 1.0, 3.0], dtype="float32")
label = paddle.to_tensor([1.0, 0.0, 1.0], dtype="float32")
bce_logit_loss = paddle.nn.BCEWithLogitsLoss()
output = bce_logit_loss(logit, label)
print(output.numpy()) # [0.45618808]
"""
def __init__(self,
weight=None,
pos_weight=None,
ignore_index=255,
edge_label=False):
super().__init__()
self.weight = weight
self.pos_weight = pos_weight
self.ignore_index = ignore_index
self.edge_label = edge_label
self.EPS = 1e-10
if self.weight is not None:
if isinstance(self.weight, str):
if self.weight != 'dynamic':
raise ValueError(
"if type of `weight` is str, it should equal to 'dynamic', but it is {}"
.format(self.weight))
elif not isinstance(self.weight, paddle.Tensor):
raise TypeError(
'The type of `weight` is wrong, it should be Tensor or str, but it is {}'
.format(type(self.weight)))
if self.pos_weight is not None:
if isinstance(self.pos_weight, str):
if self.pos_weight != 'dynamic':
raise ValueError(
"if type of `pos_weight` is str, it should equal to 'dynamic', but it is {}"
.format(self.pos_weight))
elif isinstance(self.pos_weight, float):
self.pos_weight = paddle.to_tensor(
self.pos_weight, dtype='float32')
else:
raise TypeError(
'The type of `pos_weight` is wrong, it should be float or str, but it is {}'
.format(type(self.pos_weight)))
def forward(self, logit, label):
"""
Forward computation.
Args:
logit (Tensor): Logit tensor, the data type is float32, float64. Shape is
(N, C), where C is number of classes, and if shape is more than 2D, this
is (N, C, D1, D2,..., Dk), k >= 1.
label (Tensor): Label tensor, the data type is int64. Shape is (N, C), where each
value is 0 or 1, and if shape is more than 2D, this is
(N, C, D1, D2,..., Dk), k >= 1.
"""
if len(label.shape) != len(logit.shape):
label = paddle.unsqueeze(label, 1)
mask = (label != self.ignore_index)
label = paddle.where(mask, label, paddle.zeros_like(label))
mask = paddle.cast(mask, 'float32')
# label.shape should equal to the logit.shape
if label.shape[1] != logit.shape[1]:
label = label.squeeze(1)
label = F.one_hot(label, logit.shape[1])
label = label.transpose((0, 3, 1, 2))
if isinstance(self.weight, str):
pos_index = (label == 1)
neg_index = (label == 0)
pos_num = paddle.sum(pos_index.astype('float32'))
neg_num = paddle.sum(neg_index.astype('float32'))
sum_num = pos_num + neg_num
weight_pos = 2 * neg_num / (sum_num + self.EPS)
weight_neg = 2 * pos_num / (sum_num + self.EPS)
weight = weight_pos * label + weight_neg * (1 - label)
else:
weight = self.weight
if isinstance(self.pos_weight, str):
pos_index = (label == 1)
neg_index = (label == 0)
pos_num = paddle.sum(pos_index.astype('float32'))
neg_num = paddle.sum(neg_index.astype('float32'))
sum_num = pos_num + neg_num
pos_weight = 2 * neg_num / (sum_num + self.EPS)
else:
pos_weight = self.pos_weight
label = label.astype('float32')
loss = paddle.nn.functional.binary_cross_entropy_with_logits(
logit,
label,
weight=weight,
reduction='none',
pos_weight=pos_weight)
loss = loss * mask
loss = paddle.mean(loss) / (paddle.mean(mask) + self.EPS)
label.stop_gradient = True
mask.stop_gradient = True
return loss