title: PyTorch broadcast multiplication of 4D and 2D matrix?
body: <p>How do I broadcast to multiply these two matrices together?</p>
  
  <pre><code>x: torch.Size([10, 120, 180, 30]) # (N, H, W, C)
  W: torch.Size([64, 30]) # (Y, C)
  </code></pre>
  
  <p>The output should be:</p>
  
  <pre><code>(10, 120, 180, 64) == (N, H, W, Y)
  </code></pre>