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Loss.py
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Loss.py
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# -*- coding: utf-8 -*-
"""
Created on Sun Jan 5 17:59:17 2020
@author: Lim
"""
import torch
import torch.nn as nn
import torch.nn.functional as F
def _neg_loss(pred, gt):
''' Modified focal loss. Exactly the same as CornerNet.
Runs faster and costs a little bit more memory
Arguments:
pred (batch x c x h x w)
gt_regr (batch x c x h x w)
'''
pos_inds = gt.eq(1).float()
neg_inds = gt.lt(1).float()
neg_weights = torch.pow(1 - gt, 4)
loss = 0
pos_loss = torch.log(pred) * torch.pow(1 - pred, 2) * pos_inds
neg_loss = torch.log(1 - pred) * torch.pow(pred, 2) * neg_weights * neg_inds
num_pos = pos_inds.float().sum()
pos_loss = pos_loss.sum()
neg_loss = neg_loss.sum()
if num_pos == 0:
loss = loss - neg_loss
else:
loss = loss - (pos_loss + neg_loss) / num_pos
return loss
class FocalLoss(nn.Module):
'''nn.Module warpper for focal loss'''
def __init__(self):
super(FocalLoss, self).__init__()
self.neg_loss = _neg_loss
def forward(self, pred_tensor, target_tensor):
return self.neg_loss(pred_tensor, target_tensor)
def _gather_feat(feat, ind, mask=None):
dim = feat.size(2)
ind = ind.unsqueeze(2).expand(ind.size(0), ind.size(1), dim)
feat = feat.gather(1, ind)
if mask is not None:
mask = mask.unsqueeze(2).expand_as(feat)
feat = feat[mask]
feat = feat.view(-1, dim)
return feat
def _transpose_and_gather_feat(feat, ind):
feat = feat.permute(0, 2, 3, 1).contiguous()
feat = feat.view(feat.size(0), -1, feat.size(3))
feat = _gather_feat(feat, ind)
return feat
class RegL1Loss(nn.Module):
def __init__(self):
super(RegL1Loss, self).__init__()
def forward(self, pred, mask, ind, target):
pred = _transpose_and_gather_feat(pred, ind)
mask = mask.unsqueeze(2).expand_as(pred).float()
loss = F.smooth_l1_loss(pred * mask, target * mask, reduction='sum')
loss = loss / (mask.sum() + 1e-4) # 每个目标的平均损失
return loss
def _sigmoid(x):
y = torch.clamp(x.sigmoid_(), min=1e-4, max=1-1e-4)
return y
def _relu(x):
y = torch.clamp(x.relu_(), min = 0., max=179.99)
return y
class CtdetLoss(torch.nn.Module):
# loss_weight={'hm_weight':1,'wh_weight':0.1,'reg_weight':0.1}
def __init__(self, loss_weight):
super(CtdetLoss, self).__init__()
self.crit = FocalLoss()
self.crit_reg = RegL1Loss()
self.crit_wh = RegL1Loss()
self.loss_weight = loss_weight
def forward(self, pred_tensor, target_tensor):
# for key, value in pred_tensor.items():
# print(key,':', value.size())
# for key, value in target_tensor.items():
# print(key,':', value.size())
hm_weight = self.loss_weight['hm_weight']
wh_weight = self.loss_weight['wh_weight']
reg_weight = self.loss_weight['reg_weight']
ang_weight = self.loss_weight['ang_weight']
# print(pred_tensor['hm'].size())
hm_loss, wh_loss, off_loss, ang_loss = 0, 0, 0, 0
pred_tensor['hm'] = _sigmoid(pred_tensor['hm'])
# print(target_tensor['hm'].size())
hm_loss += self.crit(pred_tensor['hm'], target_tensor['hm']) # hm_loss: focal loss该部分loss需要保留
if ang_weight > 0:
pred_tensor['ang'] = _relu(pred_tensor['ang'])
ang_loss += self.crit_wh(pred_tensor['ang'], target_tensor['reg_mask'],target_tensor['ind'], target_tensor['ang'])
if wh_weight > 0:
wh_loss += self.crit_wh(pred_tensor['wh'], target_tensor['reg_mask'],target_tensor['ind'], target_tensor['wh'])
if reg_weight > 0:
off_loss += self.crit_reg(pred_tensor['reg'], target_tensor['reg_mask'],target_tensor['ind'], target_tensor['reg'])
return hm_weight * hm_loss + wh_weight * wh_loss + reg_weight * off_loss + ang_weight * ang_loss