Pytorch 实现NonLocalBlock

import torch
import torch.nn as nn
import torchvision


class NonLocalBlock(nn.Module):
    def __init__(self, channel):
        super(NonLocalBlock, self).__init__()
        self.inter_channel = channel // 2
        self.conv_phi = nn.Conv2d(in_channels=channel, out_channels=self.inter_channel, kernel_size=1, stride=1,padding=0, bias=False)
        self.conv_theta = nn.Conv2d(in_channels=channel, out_channels=self.inter_channel, kernel_size=1, stride=1, padding=0, bias=False)
        self.conv_g = nn.Conv2d(in_channels=channel, out_channels=self.inter_channel, kernel_size=1, stride=1, padding=0, bias=False)
        self.softmax = nn.Softmax(dim=1)
        self.conv_mask = nn.Conv2d(in_channels=self.inter_channel, out_channels=channel, kernel_size=1, stride=1, padding=0, bias=False)

    def forward(self, x):
        # [N, C, H , W]
        b, c, h, w = x.size()
        # [N, C/2, H * W]
        x_phi = self.conv_phi(x).view(b, c, -1)
        # [N, H * W, C/2]
        x_theta = self.conv_theta(x).view(b, c, -1).permute(0, 2, 1).contiguous()
        x_g = self.conv_g(x).view(b, c, -1).permute(0, 2, 1).contiguous()
        # [N, H * W, H * W]
        mul_theta_phi = torch.matmul(x_theta, x_phi)
        mul_theta_phi = self.softmax(mul_theta_phi)
        # [N, H * W, C/2]
        mul_theta_phi_g = torch.matmul(mul_theta_phi, x_g)
        # [N, C/2, H, W]
        mul_theta_phi_g = mul_theta_phi_g.permute(0,2,1).contiguous().view(b,self.inter_channel, h, w)
        # [N, C, H , W]
        mask = self.conv_mask(mul_theta_phi_g)
        out = mask + x
        return out


if __name__=='__main__':
    model = NonLocalBlock(channel=16)
    print(model)

    input = torch.randn(1, 16, 64, 64)
    out = model(input)
    print(out.shape)

  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
  
26
  
27
  
28
  
29
  
30
  
31
  
32
  
33
  
34
  
35
  
36
  
37
  
38
  
39
  
40
  
41
  
42
  
43
 

文章来源: wanghao.blog.csdn.net，作者：AI浩，版权归原作者所有，如需转载，请联系作者。

原文链接：wanghao.blog.csdn.net/article/details/121567739