1 #!/usr/bin/env python 2 3 """ 4 A simple example of parallel computation using a queue and the start method. 5 """ 6 7 import pprocess 8 import time 9 #import random 10 11 # Array size and a limit on the number of processes. 12 13 N = 10 14 limit = 10 15 delay = 1 16 17 # Work function. 18 19 def calculate(i, j): 20 21 "A supposedly time-consuming calculation on 'i' and 'j'." 22 23 #time.sleep(delay * random.random()) 24 time.sleep(delay) 25 return (i, j, i * N + j) 26 27 # Main program. 28 29 if __name__ == "__main__": 30 31 t = time.time() 32 33 # Initialise the communications queue with a limit on the number of 34 # channels/processes. 35 36 queue = pprocess.Queue(limit=limit) 37 38 # Initialise an array. 39 40 results = [0] * N * N 41 42 # Wrap the calculate function. 43 44 calc = pprocess.MakeParallel(calculate) 45 46 # Perform the work. 47 48 for i in range(0, N): 49 for j in range(0, N): 50 queue.start(calc, *(i, j)) 51 52 # Store the results as they arrive. 53 54 print "Finishing..." 55 for i, j, result in queue: 56 results[i*N+j] = result 57 58 # Show the results. 59 60 for i in range(0, N): 61 for result in results[i*N:i*N+N]: 62 print result, 63 print 64 65 print "Time taken:", time.time() - t 66 67 # vim: tabstop=4 expandtab shiftwidth=4
