title: Taking a norm of matrix rows/cols in pytorch
body: <p>The norm of a vector can be taken by </p>
  
  <pre><code>torch.norm(vec)
  </code></pre>
  
  <p>However, how to take a norm of a set of vectors grouped as a matrix (either as rows or columns)?</p>
  
  <p>For example, if a matrix size is (5,8), then the rows norms should return a vector of norms of size (5).</p>