# -*- coding: utf-8 -*-
"""
Created on 18-6-7 上午10:11
@author: ronghuaiyang
"""
import torch
import torch.nn as nn
class FocalLoss(nn.Module):
def __init__(self, gamma=0, eps=1e-7):
super(FocalLoss, self).__init__()
self.gamma = gamma
self.eps = eps
self.ce = torch.nn.CrossEntropyLoss()
def forward(self, input, target):
logp = self.ce(input, target)
p = torch.exp(-logp)
loss = (1 - p) ** self.gamma * logp
return loss.mean()
