title: Python Multiprocessing: What's the difference between map and imap?
body: <p>I'm trying to learn how to use Python's multiprocessing package, but I don't understand the difference between <code>map</code> and <code>imap</code>.</p>
  
  <p>Is the difference that <code>map</code> returns, say, an actual array or set, while <code>imap</code> returns an iterator over an array or set? When would I use one over the other?</p>
  
  <p>Also, I don't understand what the chunksize argument is. Is this the number of values that are passed to each process?</p>