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# Copyright 2021 Tomoki Hayashi
# MIT License (https://opensource.org/licenses/MIT)
# Adapted by Florian Lux 2021
import torch
import torch.nn.functional as F
class FeatureMatchLoss(torch.nn.Module):
def __init__(self,
average_by_layers=False,
average_by_discriminators=False,
include_final_outputs=False, ):
super().__init__()
self.average_by_layers = average_by_layers
self.average_by_discriminators = average_by_discriminators
self.include_final_outputs = include_final_outputs
def forward(self, feats_hat, feats):
"""
Calcualate feature matching loss.
Args:
feats_hat (list): List of list of discriminator outputs
calcuated from generator outputs.
feats (list): List of list of discriminator outputs
calcuated from groundtruth.
Returns:
Tensor: Feature matching loss value.
"""
feat_match_loss = 0.0
for i, (feats_hat_, feats_) in enumerate(zip(feats_hat, feats)):
feat_match_loss_ = 0.0
if not self.include_final_outputs:
feats_hat_ = feats_hat_[:-1]
feats_ = feats_[:-1]
for j, (feat_hat_, feat_) in enumerate(zip(feats_hat_, feats_)):
feat_match_loss_ = feat_match_loss + F.l1_loss(feat_hat_, feat_.detach())
if self.average_by_layers:
feat_match_loss_ /= j + 1
feat_match_loss = feat_match_loss + feat_match_loss_
if self.average_by_discriminators:
feat_match_loss /= i + 1
return feat_match_loss