title: MXNet - multiplying scalar to an array leads to zero
body: <p>I am trying to implement tutorials of mxnet <a href="http://gluon.mxnet.io/chapter02_supervised-learning/regularization-scratch.html" rel="nofollow noreferrer">in this page</a>, in computing gradient decent:</p>
  
  <pre><code>def SGD(params, lr):
  for param in params:
      param[:] = param - lr * param.grad
  </code></pre>
  
  <p>I noticed that when lr&lt;1,  the scalar to array multiplication </p>
  
  <pre><code>lr * param.grad
  </code></pre>
  
  <p>becomes a zero matrix with same size of param.grad</p>
  
  <p>I do not  know why this happens. can any one help me to understand this?</p>
  
  <p>Many thanks</p>