写一个可以直接用的arcface loss
时间: 2023-09-08 13:10:46 浏览: 78
好的,以下是一个可以直接用的 ArcFace Loss 的代码实现:
```python
import torch.nn as nn
import torch.nn.functional as F
class ArcFaceLoss(nn.Module):
def __init__(self, in_features, out_features, s=30.0, m=0.50):
super(ArcFaceLoss, self).__init__()
self.in_features = in_features
self.out_features = out_features
self.s = s
self.m = m
self.weight = nn.Parameter(torch.FloatTensor(out_features, in_features))
nn.init.xavier_uniform_(self.weight)
def forward(self, input, target):
cosine = F.linear(F.normalize(input), F.normalize(self.weight))
theta = torch.acos(torch.clamp(cosine, -1.0 + 1e-7, 1.0 - 1e-7))
margins = torch.zeros_like(cosine)
margins.scatter_(1, target.view(-1, 1).long(), self.m)
cos_m = torch.cos(margins)
sin_m = torch.sin(margins)
cos_theta = torch.cos(theta)
sin_theta = torch.sin(theta)
cos_theta_m = cos_theta * cos_m - sin_theta * sin_m
output = cos_theta * 1.0
output.scatter_(1, target.view(-1, 1).long(), cos_theta_m.view(-1, 1))
output *= self.s
return output
```
其中,`in_features` 表示输入特征的维度,`out_features` 表示输出的类别数,`s` 表示缩放因子,`m` 表示 margin。在 `forward` 方法中,首先对输入向量进行 L2 归一化,然后计算输入向量与权重矩阵的相似度得到余弦值,再根据余弦值计算出角度值 theta,接着构造 margins 张量,用于计算 margin,然后计算出 cos(margin) 与 sin(margin),cos(theta) 与 sin(theta),最后根据公式计算出 ArcFace Loss。