RuntimeError: mat1 and mat2 shapes cannot be multiplied (1024x1 and 1024x3)

前言：学习pytorch 在构建神经网络时，发现了测试网络RuntimeError: mat1 and mat2 shapes cannot be multiplied (1024x1 and 1024x3)记录错误。

Traceback (most recent call last):   File "mobilenet_v1.py", line 145, in <module>     out = model(input)   File "J:\WorkSoft\envs\yolov5_test\lib\site-packages\torch\nn\modules\module.py", line 1051, in _call_impl     return forward_call(*input, **kwargs)   File "mobilenet_v1.py", line 138, in forward     x = self.fc(x)   File "J:\WorkSoft\envs\yolov5_test\lib\site-packages\torch\nn\modules\module.py", line 1051, in _call_impl     return forward_call(*input, **kwargs)   File "J:\WorkSoft\envs\yolov5_test\lib\site-packages\torch\nn\modules\linear.py", line 96, in forward     return F.linear(input, self.weight, self.bias)   File "J:\WorkSoft\envs\yolov5_test\lib\site-packages\torch\nn\functional.py", line 1847, in linear     return torch._C._nn.linear(input, weight, bias) RuntimeError: mat1 and mat2 shapes cannot be multiplied (1024x1 and 1024x3) 

 File "mobilenet_v1.py", line 138, in forward     x = self.
       
        fc
        (x
        ) 
       

卷积层的输入为四维[batch_size,channels,H,W] ，而全连接接受维度为2的输入，通常为[batch_size, size]。

在全连接层前面加入维度变换

//方法一：
x.view(-1,7* 7* 1024) 

//方法二：
x = torch.flatten(x,1) //拉成二维向量[batch_size, size]