models/aslloss.py

"""
    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