loss.py

# coding: utf8
# copyright (c) 2019 PaddlePaddle Authors. All Rights Reserve.
#
# 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.

import sys
import paddle.fluid as fluid
import numpy as np
import importlib
from utils.config import cfg


def softmax_with_loss(logit, label, ignore_mask=None, num_classes=2):
    ignore_mask = fluid.layers.cast(ignore_mask, 'float32')
    label = fluid.layers.elementwise_min(
        label, fluid.layers.assign(np.array([num_classes - 1], dtype=np.int32)))
    logit = fluid.layers.transpose(logit, [0, 2, 3, 1])
    logit = fluid.layers.reshape(logit, [-1, num_classes])
    label = fluid.layers.reshape(label, [-1, 1])
    label = fluid.layers.cast(label, 'int64')
    ignore_mask = fluid.layers.reshape(ignore_mask, [-1, 1])
    loss, probs = fluid.layers.softmax_with_cross_entropy(
        logit,
        label,
        ignore_index=cfg.DATASET.IGNORE_INDEX,
        return_softmax=True)

    loss = loss * ignore_mask
    if cfg.MODEL.FP16:
        loss = fluid.layers.cast(loss, 'float32')
        avg_loss = fluid.layers.mean(loss) / fluid.layers.mean(ignore_mask)
        avg_loss = fluid.layers.cast(avg_loss, 'float16')
    else:
        avg_loss = fluid.layers.mean(loss) / fluid.layers.mean(ignore_mask)
    if cfg.MODEL.SCALE_LOSS > 1.0:
        avg_loss = avg_loss * cfg.MODEL.SCALE_LOSS
    label.stop_gradient = True
    ignore_mask.stop_gradient = True
    return avg_loss


def multi_softmax_with_loss(logits, label, ignore_mask=None, num_classes=2):
    if isinstance(logits, tuple):
        avg_loss = 0
        for i, logit in enumerate(logits):
            logit_label = fluid.layers.resize_nearest(label, logit.shape[2:])
            logit_mask = (logit_label.astype('int32') !=
                          cfg.DATASET.IGNORE_INDEX).astype('int32')
            loss = softmax_with_loss(logit, logit_label, logit_mask,
                                     num_classes)
            avg_loss += cfg.MODEL.MULTI_LOSS_WEIGHT[i] * loss
    else:
        avg_loss = softmax_with_loss(logits, label, ignore_mask, num_classes)
    return avg_loss


# to change, how to appicate ignore index and ignore mask
def dice_loss(logit, label, ignore_mask=None, num_classes=2):
    if num_classes != 2:
        raise Exception("dice loss is only applicable to binary classfication")
    ignore_mask = fluid.layers.cast(ignore_mask, 'float32')
    label = fluid.layers.elementwise_min(
        label, fluid.layers.assign(np.array([num_classes - 1], dtype=np.int32)))
    logit = fluid.layers.transpose(logit, [0, 2, 3, 1])
    logit = fluid.layers.reshape(logit, [-1, num_classes])
    logit = fluid.layers.softmax(logit)
    label = fluid.layers.reshape(label, [-1, 1])
    label = fluid.layers.cast(label, 'int64')
    ignore_mask = fluid.layers.reshape(ignore_mask, [-1, 1])
    loss = fluid.layers.dice_loss(logit, label)
    label.stop_gradient = True
    ignore_mask.stop_gradient = True
    return loss