1 #!/usr/bin/env python 2 3 """ 4 A simple example of parallel computation using message queues and the create 5 function. 6 7 NOTE: We could use the with statement in the innermost loop to package the 8 NOTE: try...finally functionality. 9 """ 10 11 import pprocess 12 import time 13 #import random 14 15 # Array size and a limit on the number of processes. 16 17 N = 10 18 limit = 10 19 delay = 1 20 21 # Main program. 22 23 if __name__ == "__main__": 24 25 t = time.time() 26 27 # Initialise the communications queue with a limit on the number of 28 # channels/processes. 29 30 queue = pprocess.Queue(limit=limit) 31 32 # Initialise an array. 33 34 results = [0] * N * N 35 36 # Perform the work. 37 # NOTE: Could use the with statement in the loop to package the 38 # NOTE: try...finally functionality. 39 40 print "Calculating..." 41 for i in range(0, N): 42 for j in range(0, N): 43 ch = queue.create() 44 if ch: 45 try: # Calculation work. 46 47 #time.sleep(delay * random.random()) 48 time.sleep(delay) 49 ch.send((i, j, i * N + j)) 50 51 finally: # Important finalisation. 52 53 pprocess.exit(ch) 54 55 # Store the results as they arrive. 56 57 print "Finishing..." 58 for i, j, result in queue: 59 results[i*N+j] = result 60 61 # Show the results. 62 63 for i in range(0, N): 64 for result in results[i*N:i*N+N]: 65 print result, 66 print 67 68 print "Time taken:", time.time() - t 69 70 # vim: tabstop=4 expandtab shiftwidth=4
