title: multiprocessing: map vs map_async
body: <p>What's the difference between using <code>map</code> and <code>map_async</code>?  Are they not running the same function after distributing the items from the list to 4 processes?</p>
  
  <p>So is it wrong to presume both are running asynchronous and parallel?</p>
  
  <pre><code>def f(x):
     return 2*x
  
  p=Pool(4)
  l=[1,2,3,4]
  out1=p.map(f,l)
  #vs
  out2=p.map_async(f,l)
  </code></pre>