title: multiprocessing Pool without return value?
body: <p>I am trying to use a multiprocessing <code>Pool</code> without a return value for parallel calculation. It could be faster if there's no need to return and retrieve values from the subprocess. Is there a way to do that?</p>
  
  <p>Here is a simple example:</p>
  
  <pre><code>from multiprocessing import Pool
  
  def fun(a):
      # do something.. 
      a["1"]=100
  
  a={
     "1":12
     }
  multi = [a] * 10
  p = Pool(4)
  p.map(fun, multi)
  data = [a["1"] for a in multi]
  print(data)
  &gt;&gt;&gt; [12, 12, 12, 12, 12, 12, 12, 12, 12, 12]
  
  [fun(a) for a in multi]
  data = [a["1"] for a in multi]
  print(data)
  &gt;&gt;&gt; [100, 100, 100, 100, 100, 100, 100, 100, 100, 100]
  </code></pre>
  
  <p>Does anybody know why? And is there a solution for that?</p>