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"""
Most borrow from: https://github.com/Alibaba-MIIL/ASL
"""
import torch
import torch.nn as nn
class AsymmetricLoss(nn.Module):
def __init__(self, gamma_neg=4, gamma_pos=1, clip=0.05, eps=1e-8, disable_torch_grad_focal_loss=False):
super(AsymmetricLoss, self).__init__()
self.gamma_neg = gamma_neg
self.gamma_pos = gamma_pos
self.clip = clip
self.disable_torch_grad_focal_loss = disable_torch_grad_focal_loss
self.eps = eps
def forward(self, x, y):
""""
Parameters
----------
x: input logits
y: targets (multi-label binarized vector)
"""
# Calculating Probabilities
x_sigmoid = torch.sigmoid(x)
xs_pos = x_sigmoid
xs_neg = 1 - x_sigmoid
# Asymmetric Clipping
if self.clip is not None and self.clip > 0:
xs_neg = (xs_neg + self.clip).clamp(max=1)
# Basic CE calculation
los_pos = y * torch.log(xs_pos.clamp(min=self.eps, max=1-self.eps))
los_neg = (1 - y) * torch.log(xs_neg.clamp(min=self.eps, max=1-self.eps))
loss = los_pos + los_neg
# Asymmetric Focusing
if self.gamma_neg > 0 or self.gamma_pos > 0:
if self.disable_torch_grad_focal_loss:
torch._C.set_grad_enabled(False)
pt0 = xs_pos * y
pt1 = xs_neg * (1 - y) # pt = p if t > 0 else 1-p
pt = pt0 + pt1
one_sided_gamma = self.gamma_pos * y + self.gamma_neg * (1 - y)
one_sided_w = torch.pow(1 - pt, one_sided_gamma)
if self.disable_torch_grad_focal_loss:
torch._C.set_grad_enabled(True)
loss *= one_sided_w
return -loss.sum()
class AsymmetricLossOptimized(nn.Module):
''' Notice - optimized version, minimizes memory allocation and gpu uploading,
favors inplace operations'''
def __init__(self, gamma_neg=4, gamma_pos=1, clip=0.05, eps=1e-5, disable_torch_grad_focal_loss=False):
super(AsymmetricLossOptimized, self).__init__()
self.gamma_neg = gamma_neg
self.gamma_pos = gamma_pos
self.clip = clip
self.disable_torch_grad_focal_loss = disable_torch_grad_focal_loss
self.eps = eps
self.targets = self.anti_targets = self.xs_pos = self.xs_neg = self.asymmetric_w = self.loss = None
def forward(self, x, y):
""""
Parameters
----------
x: input logits
y: targets (multi-label binarized vector)
"""
self.targets = y
self.anti_targets = 1 - y
# Calculating Probabilities
self.xs_pos = torch.sigmoid(x)
self.xs_neg = 1.0 - self.xs_pos
# Asymmetric Clipping
if self.clip is not None and self.clip > 0:
self.xs_neg.add_(self.clip).clamp_(max=1)
# Basic CE calculation
self.loss = self.targets * torch.log(self.xs_pos.clamp(min=self.eps))
self.loss.add_(self.anti_targets * torch.log(self.xs_neg.clamp(min=self.eps)))
# Asymmetric Focusing
if self.gamma_neg > 0 or self.gamma_pos > 0:
if self.disable_torch_grad_focal_loss:
with torch.no_grad():
# if self.disable_torch_grad_focal_loss:
# torch._C.set_grad_enabled(False)
self.xs_pos = self.xs_pos * self.targets
self.xs_neg = self.xs_neg * self.anti_targets
self.asymmetric_w = torch.pow(1 - self.xs_pos - self.xs_neg,
self.gamma_pos * self.targets + self.gamma_neg * self.anti_targets)
# if self.disable_torch_grad_focal_loss:
# torch._C.set_grad_enabled(True)
self.loss *= self.asymmetric_w
else:
self.xs_pos = self.xs_pos * self.targets
self.xs_neg = self.xs_neg * self.anti_targets
self.asymmetric_w = torch.pow(1 - self.xs_pos - self.xs_neg,
self.gamma_pos * self.targets + self.gamma_neg * self.anti_targets)
self.loss *= self.asymmetric_w
_loss = - self.loss.sum() / x.size(0)
_loss = _loss / y.size(1) * 1000
return _loss
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