title: Python multiprocessing of a sum
body: <p>I dont get my code to run, and as others, i have problems in understand how multiprocessing works. here is my code so far</p>
  
  <pre><code>if __name__ == "__main__":
      start = time.clock()
      bins = np.linspace(0,5 * 2 ** 15, 2 ** 15, endpoint=False)  # 1e3
      t_full = np.linspace(0, 0.2, 2 * bins.shape[0], endpoint=False)
      po = Pool()
      res = po.map_async(timeseries, ((m, n, params, bins, 1, t_full, i, i + 1) for i in xrange(2 ** 15)))
      signal = sum(res.get())
  </code></pre>
  
  <p>where timeseries is given by</p>
  
  <pre><code>def timeseries_para(m, n, params, bins, seed, t, sum_min, sum_max):
      np.random.seed(seed)
  
      PSD_data = PSD(m, n, params, bins)
      dataReal = np.empty_like(PSD_data)
  
      for i in range(bins.shape[0]):
          dataReal[i] = np.random.normal(PSD_data[i], 0.1 * PSD_data[i]) 
  
      plt.loglog(bins, dataReal, 'red')
  
      dataCOS = np.sqrt(dataReal)
      signal = np.zeros(t.shape[0]) 
  
      ## Calculating timeseries
      #for i in range(bins.shape[0]):
      for i in range(sum_min, sum_max):
          #start = time.clock()
          signal += dataCOS[i] * np.cos(2 * np.pi * t * bins[i] + random.uniform(0, 2 * np.pi))  
          #print time.clock() - start        
  
      return signal
  </code></pre>
  
  <p>My sum goes from 0 up to 2**16, so speeding this up is essential. My problem is, that i first don't know how call my function correct and how i can sum all my replies up. </p>
  
  <p>Thanks for any advice!</p>