# Source code for espnet2.spk.loss.aamsoftmax

#! /usr/bin/python
# -*- encoding: utf-8 -*-
# code from https://github.com/clovaai/voxceleb_trainer/blob/master/loss/aamsoftmax.py

import math

import torch
import torch.nn as nn
import torch.nn.functional as F

from espnet2.spk.loss.abs_loss import AbsLoss

[docs]class AAMSoftmax(AbsLoss):

Paper: Deng, Jiankang, et al. "Arcface: Additive angular margin loss for
deep face recognition." Proceedings of the IEEE/CVF conference on computer
vision and pattern recognition. 2019.

args:
nout    : dimensionality of speaker embedding
nclases: number of speakers in the training set
margin  : margin value of AAMSoftmax
scale   : scale value of AAMSoftmax
"""

def __init__(
self, nout, nclasses, margin=0.3, scale=15, easy_margin=False, **kwargs
):
super().__init__(nout)

self.test_normalize = True

self.m = margin
self.s = scale
self.in_feats = nout
self.weight = torch.nn.Parameter(
)
self.ce = nn.CrossEntropyLoss()
nn.init.xavier_normal_(self.weight, gain=1)

self.easy_margin = easy_margin
self.cos_m = math.cos(self.m)
self.sin_m = math.sin(self.m)

# make the function cos(theta+m) monotonic decreasing while theta in [0°,180°]
self.th = math.cos(math.pi - self.m)
self.mm = math.sin(math.pi - self.m) * self.m

print("Initialised AAMSoftmax margin %.3f scale %.3f" % (self.m, self.s))

[docs]    def forward(self, x, label=None):
if len(label.size()) == 2:
label = label.squeeze(1)

assert x.size()[0] == label.size()[0]
assert x.size()[1] == self.in_feats

# cos(theta)
cosine = F.linear(F.normalize(x), F.normalize(self.weight))
# cos(theta + m)
sine = torch.sqrt((1.0 - torch.mul(cosine, cosine)).clamp(0, 1))
phi = cosine * self.cos_m - sine * self.sin_m

if self.easy_margin:
phi = torch.where(cosine > 0, phi, cosine)
else:
phi = torch.where((cosine - self.th) > 0, phi, cosine - self.mm)

one_hot = torch.zeros_like(cosine)
one_hot.scatter_(1, label.view(-1, 1), 1)
output = (one_hot * phi) + ((1.0 - one_hot) * cosine)
output = output * self.s

loss = self.ce(output, label)
return loss