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- # Copyright (c) 2021 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 math
- class ArcMargin(nn.Layer):
- def __init__(self,
- embedding_size,
- class_num,
- margin=0.5,
- scale=80.0,
- easy_margin=False):
- super().__init__()
- self.embedding_size = embedding_size
- self.class_num = class_num
- self.margin = margin
- self.scale = scale
- self.easy_margin = easy_margin
- self.weight = self.create_parameter(
- shape=[self.embedding_size, self.class_num],
- is_bias=False,
- default_initializer=paddle.nn.initializer.XavierNormal())
- def forward(self, input, label=None):
- input_norm = paddle.sqrt(
- paddle.sum(paddle.square(input), axis=1, keepdim=True))
- input = paddle.divide(input, input_norm)
- weight_norm = paddle.sqrt(
- paddle.sum(paddle.square(self.weight), axis=0, keepdim=True))
- weight = paddle.divide(self.weight, weight_norm)
- cos = paddle.matmul(input, weight)
- if not self.training or label is None:
- return cos
- sin = paddle.sqrt(1.0 - paddle.square(cos) + 1e-6)
- cos_m = math.cos(self.margin)
- sin_m = math.sin(self.margin)
- phi = cos * cos_m - sin * sin_m
- th = math.cos(self.margin) * (-1)
- mm = math.sin(self.margin) * self.margin
- if self.easy_margin:
- phi = self._paddle_where_more_than(cos, 0, phi, cos)
- else:
- phi = self._paddle_where_more_than(cos, th, phi, cos - mm)
- one_hot = paddle.nn.functional.one_hot(label, self.class_num)
- one_hot = paddle.squeeze(one_hot, axis=[1])
- output = paddle.multiply(one_hot, phi) + paddle.multiply(
- (1.0 - one_hot), cos)
- output = output * self.scale
- return output
- def _paddle_where_more_than(self, target, limit, x, y):
- mask = paddle.cast(x=(target > limit), dtype='float32')
- output = paddle.multiply(mask, x) + paddle.multiply((1.0 - mask), y)
- return output
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