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# coding=utf-8 | |
# Copyright 2022 The IDEA Authors. All rights reserved. | |
# | |
# Licensed under the Apache License, Version 2.0 (the "License"); | |
# you may not use this file except in compliance with the License. | |
# You may obtain a copy of the License at | |
# | |
# http://www.apache.org/licenses/LICENSE-2.0 | |
# | |
# Unless required by applicable law or agreed to in writing, software | |
# distributed under the License is distributed on an "AS IS" BASIS, | |
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
# See the License for the specific language governing permissions and | |
# limitations under the License. | |
# ------------------------------------------------------------------------------------------------ | |
# Copyright (c) OpenMMLab. All rights reserved. | |
# ------------------------------------------------------------------------------------------------ | |
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/losses/utils.py | |
# ------------------------------------------------------------------------------------------------ | |
import torch | |
import torch.nn.functional as F | |
def reduce_loss(loss, reduction): | |
"""Reduce loss as specified | |
Args: | |
loss (nn.Tensor): Elementwise loss tensor. | |
reduction (str): Specified reduction function chosen from "none", | |
"mean" and "sum". | |
Return: | |
nn.Tensor: Reduced loss tensor. | |
""" | |
reduction_enum = F._Reduction.get_enum(reduction) | |
# none: 0, elementwise_mean:1, sum: 2 | |
if reduction_enum == 0: | |
return loss | |
elif reduction_enum == 1: | |
return loss.mean() | |
elif reduction_enum == 2: | |
return loss.sum() | |
def weight_reduce_loss(loss, weight=None, reduction="mean", avg_factor=None): | |
"""Apply element-wise weight and reduce loss. | |
Args: | |
loss (Tensor): Element-wise loss. | |
weight (Tensor): Element-wise weights. | |
reduction (str): Same as built-in losses of PyTorch. | |
avg_factor (float): Average factor when computing the mean of losses. | |
Returns: | |
Tensor: Processed loss values. | |
""" | |
# if weight is specified, apply element-wise weight | |
if weight is not None: | |
loss = loss * weight | |
# if avg_factor is not specified, just reduce the loss | |
if avg_factor is None: | |
loss = reduce_loss(loss, reduction) | |
else: | |
# if reduction is mean, then average the loss by avg_factor | |
if reduction == "mean": | |
# Avoid causing ZeroDivisionError when avg_factor is 0.0. | |
eps = torch.finfo(loss.dtype).eps | |
loss = loss.sum() / (avg_factor + eps) | |
# if reduction is 'none', then do nothing, otherwise raise an error | |
elif reduction != "none": | |
raise ValueError('avg_factor can not be used with reduction="sum"') | |
return loss | |