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import math
import torch
from torch import autograd as autograd
from torch import nn as nn
from torch.nn import functional as F
from basicsr.archs.vgg_arch import VGGFeatureExtractor
from basicsr.utils.registry import LOSS_REGISTRY
from .loss_util import weighted_loss
_reduction_modes = ['none', 'mean', 'sum']
@weighted_loss
def l1_loss(pred, target):
return F.l1_loss(pred, target, reduction='none')
@weighted_loss
def mse_loss(pred, target):
return F.mse_loss(pred, target, reduction='none')
@weighted_loss
def charbonnier_loss(pred, target, eps=1e-12):
return torch.sqrt((pred - target)**2 + eps)
@LOSS_REGISTRY.register()
class L1Loss(nn.Module):
"""L1 (mean absolute error, MAE) loss.
Args:
loss_weight (float): Loss weight for L1 loss. Default: 1.0.
reduction (str): Specifies the reduction to apply to the output.
Supported choices are 'none' | 'mean' | 'sum'. Default: 'mean'.
"""
def __init__(self, loss_weight=1.0, reduction='mean'):
super(L1Loss, self).__init__()
if reduction not in ['none', 'mean', 'sum']:
raise ValueError(f'Unsupported reduction mode: {reduction}. ' f'Supported ones are: {_reduction_modes}')
self.loss_weight = loss_weight
self.reduction = reduction
def forward(self, pred, target, weight=None, **kwargs):
"""
Args:
pred (Tensor): of shape (N, C, H, W). Predicted tensor.
target (Tensor): of shape (N, C, H, W). Ground truth tensor.
weight (Tensor, optional): of shape (N, C, H, W). Element-wise
weights. Default: None.
"""
return self.loss_weight * l1_loss(pred, target, weight, reduction=self.reduction)
@LOSS_REGISTRY.register()
class MSELoss(nn.Module):
"""MSE (L2) loss.
Args:
loss_weight (float): Loss weight for MSE loss. Default: 1.0.
reduction (str): Specifies the reduction to apply to the output.
Supported choices are 'none' | 'mean' | 'sum'. Default: 'mean'.
"""
def __init__(self, loss_weight=1.0, reduction='mean'):
super(MSELoss, self).__init__()
if reduction not in ['none', 'mean', 'sum']:
raise ValueError(f'Unsupported reduction mode: {reduction}. ' f'Supported ones are: {_reduction_modes}')
self.loss_weight = loss_weight
self.reduction = reduction
def forward(self, pred, target, weight=None, **kwargs):
"""
Args:
pred (Tensor): of shape (N, C, H, W). Predicted tensor.
target (Tensor): of shape (N, C, H, W). Ground truth tensor.
weight (Tensor, optional): of shape (N, C, H, W). Element-wise
weights. Default: None.
"""
return self.loss_weight * mse_loss(pred, target, weight, reduction=self.reduction)
@LOSS_REGISTRY.register()
class CharbonnierLoss(nn.Module):
"""Charbonnier loss (one variant of Robust L1Loss, a differentiable
variant of L1Loss).
Described in "Deep Laplacian Pyramid Networks for Fast and Accurate
Super-Resolution".
Args:
loss_weight (float): Loss weight for L1 loss. Default: 1.0.
reduction (str): Specifies the reduction to apply to the output.
Supported choices are 'none' | 'mean' | 'sum'. Default: 'mean'.
eps (float): A value used to control the curvature near zero.
Default: 1e-12.
"""
def __init__(self, loss_weight=1.0, reduction='mean', eps=1e-12):
super(CharbonnierLoss, self).__init__()
if reduction not in ['none', 'mean', 'sum']:
raise ValueError(f'Unsupported reduction mode: {reduction}. ' f'Supported ones are: {_reduction_modes}')
self.loss_weight = loss_weight
self.reduction = reduction
self.eps = eps
def forward(self, pred, target, weight=None, **kwargs):
"""
Args:
pred (Tensor): of shape (N, C, H, W). Predicted tensor.
target (Tensor): of shape (N, C, H, W). Ground truth tensor.
weight (Tensor, optional): of shape (N, C, H, W). Element-wise
weights. Default: None.
"""
return self.loss_weight * charbonnier_loss(pred, target, weight, eps=self.eps, reduction=self.reduction)
@LOSS_REGISTRY.register()
class WeightedTVLoss(L1Loss):
"""Weighted TV loss.
Args:
loss_weight (float): Loss weight. Default: 1.0.
"""
def __init__(self, loss_weight=1.0):
super(WeightedTVLoss, self).__init__(loss_weight=loss_weight)
def forward(self, pred, weight=None):
y_diff = super(WeightedTVLoss, self).forward(pred[:, :, :-1, :], pred[:, :, 1:, :], weight=weight[:, :, :-1, :])
x_diff = super(WeightedTVLoss, self).forward(pred[:, :, :, :-1], pred[:, :, :, 1:], weight=weight[:, :, :, :-1])
loss = x_diff + y_diff
return loss
@LOSS_REGISTRY.register()
class PerceptualLoss(nn.Module):
"""Perceptual loss with commonly used style loss.
Args:
layer_weights (dict): The weight for each layer of vgg feature.
Here is an example: {'conv5_4': 1.}, which means the conv5_4
feature layer (before relu5_4) will be extracted with weight
1.0 in calculting losses.
vgg_type (str): The type of vgg network used as feature extractor.
Default: 'vgg19'.
use_input_norm (bool): If True, normalize the input image in vgg.
Default: True.
range_norm (bool): If True, norm images with range [-1, 1] to [0, 1].
Default: False.
perceptual_weight (float): If `perceptual_weight > 0`, the perceptual
loss will be calculated and the loss will multiplied by the
weight. Default: 1.0.
style_weight (float): If `style_weight > 0`, the style loss will be
calculated and the loss will multiplied by the weight.
Default: 0.
criterion (str): Criterion used for perceptual loss. Default: 'l1'.
"""
def __init__(self,
layer_weights,
vgg_type='vgg19',
use_input_norm=True,
range_norm=False,
perceptual_weight=1.0,
style_weight=0.,
criterion='l1'):
super(PerceptualLoss, self).__init__()
self.perceptual_weight = perceptual_weight
self.style_weight = style_weight
self.layer_weights = layer_weights
self.vgg = VGGFeatureExtractor(
layer_name_list=list(layer_weights.keys()),
vgg_type=vgg_type,
use_input_norm=use_input_norm,
range_norm=range_norm)
self.criterion_type = criterion
if self.criterion_type == 'l1':
self.criterion = torch.nn.L1Loss()
elif self.criterion_type == 'l2':
self.criterion = torch.nn.L2loss()
elif self.criterion_type == 'fro':
self.criterion = None
else:
raise NotImplementedError(f'{criterion} criterion has not been supported.')
def forward(self, x, gt):
"""Forward function.
Args:
x (Tensor): Input tensor with shape (n, c, h, w).
gt (Tensor): Ground-truth tensor with shape (n, c, h, w).
Returns:
Tensor: Forward results.
"""
# extract vgg features
x_features = self.vgg(x)
gt_features = self.vgg(gt.detach())
# calculate perceptual loss
if self.perceptual_weight > 0:
percep_loss = 0
for k in x_features.keys():
if self.criterion_type == 'fro':
percep_loss += torch.norm(x_features[k] - gt_features[k], p='fro') * self.layer_weights[k]
else:
percep_loss += self.criterion(x_features[k], gt_features[k]) * self.layer_weights[k]
percep_loss *= self.perceptual_weight
else:
percep_loss = None
# calculate style loss
if self.style_weight > 0:
style_loss = 0
for k in x_features.keys():
if self.criterion_type == 'fro':
style_loss += torch.norm(
self._gram_mat(x_features[k]) - self._gram_mat(gt_features[k]), p='fro') * self.layer_weights[k]
else:
style_loss += self.criterion(self._gram_mat(x_features[k]), self._gram_mat(
gt_features[k])) * self.layer_weights[k]
style_loss *= self.style_weight
else:
style_loss = None
return percep_loss, style_loss
def _gram_mat(self, x):
"""Calculate Gram matrix.
Args:
x (torch.Tensor): Tensor with shape of (n, c, h, w).
Returns:
torch.Tensor: Gram matrix.
"""
n, c, h, w = x.size()
features = x.view(n, c, w * h)
features_t = features.transpose(1, 2)
gram = features.bmm(features_t) / (c * h * w)
return gram
@LOSS_REGISTRY.register()
class GANLoss(nn.Module):
"""Define GAN loss.
Args:
gan_type (str): Support 'vanilla', 'lsgan', 'wgan', 'hinge'.
real_label_val (float): The value for real label. Default: 1.0.
fake_label_val (float): The value for fake label. Default: 0.0.
loss_weight (float): Loss weight. Default: 1.0.
Note that loss_weight is only for generators; and it is always 1.0
for discriminators.
"""
def __init__(self, gan_type, real_label_val=1.0, fake_label_val=0.0, loss_weight=1.0):
super(GANLoss, self).__init__()
self.gan_type = gan_type
self.loss_weight = loss_weight
self.real_label_val = real_label_val
self.fake_label_val = fake_label_val
if self.gan_type == 'vanilla':
self.loss = nn.BCEWithLogitsLoss()
elif self.gan_type == 'lsgan':
self.loss = nn.MSELoss()
elif self.gan_type == 'wgan':
self.loss = self._wgan_loss
elif self.gan_type == 'wgan_softplus':
self.loss = self._wgan_softplus_loss
elif self.gan_type == 'hinge':
self.loss = nn.ReLU()
else:
raise NotImplementedError(f'GAN type {self.gan_type} is not implemented.')
def _wgan_loss(self, input, target):
"""wgan loss.
Args:
input (Tensor): Input tensor.
target (bool): Target label.
Returns:
Tensor: wgan loss.
"""
return -input.mean() if target else input.mean()
def _wgan_softplus_loss(self, input, target):
"""wgan loss with soft plus. softplus is a smooth approximation to the
ReLU function.
In StyleGAN2, it is called:
Logistic loss for discriminator;
Non-saturating loss for generator.
Args:
input (Tensor): Input tensor.
target (bool): Target label.
Returns:
Tensor: wgan loss.
"""
return F.softplus(-input).mean() if target else F.softplus(input).mean()
def get_target_label(self, input, target_is_real):
"""Get target label.
Args:
input (Tensor): Input tensor.
target_is_real (bool): Whether the target is real or fake.
Returns:
(bool | Tensor): Target tensor. Return bool for wgan, otherwise,
return Tensor.
"""
if self.gan_type in ['wgan', 'wgan_softplus']:
return target_is_real
target_val = (self.real_label_val if target_is_real else self.fake_label_val)
return input.new_ones(input.size()) * target_val
def forward(self, input, target_is_real, is_disc=False):
"""
Args:
input (Tensor): The input for the loss module, i.e., the network
prediction.
target_is_real (bool): Whether the targe is real or fake.
is_disc (bool): Whether the loss for discriminators or not.
Default: False.
Returns:
Tensor: GAN loss value.
"""
target_label = self.get_target_label(input, target_is_real)
if self.gan_type == 'hinge':
if is_disc: # for discriminators in hinge-gan
input = -input if target_is_real else input
loss = self.loss(1 + input).mean()
else: # for generators in hinge-gan
loss = -input.mean()
else: # other gan types
loss = self.loss(input, target_label)
# loss_weight is always 1.0 for discriminators
return loss if is_disc else loss * self.loss_weight
def r1_penalty(real_pred, real_img):
"""R1 regularization for discriminator. The core idea is to
penalize the gradient on real data alone: when the
generator distribution produces the true data distribution
and the discriminator is equal to 0 on the data manifold, the
gradient penalty ensures that the discriminator cannot create
a non-zero gradient orthogonal to the data manifold without
suffering a loss in the GAN game.
Ref:
Eq. 9 in Which training methods for GANs do actually converge.
"""
grad_real = autograd.grad(outputs=real_pred.sum(), inputs=real_img, create_graph=True)[0]
grad_penalty = grad_real.pow(2).view(grad_real.shape[0], -1).sum(1).mean()
return grad_penalty
def g_path_regularize(fake_img, latents, mean_path_length, decay=0.01):
noise = torch.randn_like(fake_img) / math.sqrt(fake_img.shape[2] * fake_img.shape[3])
grad = autograd.grad(outputs=(fake_img * noise).sum(), inputs=latents, create_graph=True)[0]
path_lengths = torch.sqrt(grad.pow(2).sum(2).mean(1))
path_mean = mean_path_length + decay * (path_lengths.mean() - mean_path_length)
path_penalty = (path_lengths - path_mean).pow(2).mean()
return path_penalty, path_lengths.detach().mean(), path_mean.detach()
def gradient_penalty_loss(discriminator, real_data, fake_data, weight=None):
"""Calculate gradient penalty for wgan-gp.
Args:
discriminator (nn.Module): Network for the discriminator.
real_data (Tensor): Real input data.
fake_data (Tensor): Fake input data.
weight (Tensor): Weight tensor. Default: None.
Returns:
Tensor: A tensor for gradient penalty.
"""
batch_size = real_data.size(0)
alpha = real_data.new_tensor(torch.rand(batch_size, 1, 1, 1))
# interpolate between real_data and fake_data
interpolates = alpha * real_data + (1. - alpha) * fake_data
interpolates = autograd.Variable(interpolates, requires_grad=True)
disc_interpolates = discriminator(interpolates)
gradients = autograd.grad(
outputs=disc_interpolates,
inputs=interpolates,
grad_outputs=torch.ones_like(disc_interpolates),
create_graph=True,
retain_graph=True,
only_inputs=True)[0]
if weight is not None:
gradients = gradients * weight
gradients_penalty = ((gradients.norm(2, dim=1) - 1)**2).mean()
if weight is not None:
gradients_penalty /= torch.mean(weight)
return gradients_penalty