title: Utility of parameter 'out' in numpy functions
body: <p>What is the utility of the <code>out</code> parameter in certain <code>numpy</code> functions such as <code>cumsum</code> or <code>cumprod</code> or other mathematical functions?</p>
  
  <p>If the result is huge in size does it help to use the <code>out</code> parameter to improve computational time or memory efficiency?</p>
  
  <p><a href="https://stackoverflow.com/questions/20041570/numpy-ceil-and-floor-out-argument">This thread</a> gives some information about <em>how</em> to use it. But I want to know <em>when</em> should I use it and what could the benefits be?</p>