paul@161 | 1 | #!/usr/bin/env python |
paul@161 | 2 | |
paul@161 | 3 | """ |
paul@161 | 4 | A simple example of parallel computation using a queue and continuous |
paul@161 | 5 | communications. |
paul@161 | 6 | """ |
paul@161 | 7 | |
paul@161 | 8 | import pprocess |
paul@161 | 9 | import time |
paul@161 | 10 | #import random |
paul@161 | 11 | |
paul@161 | 12 | # Array size and a limit on the number of processes. |
paul@161 | 13 | |
paul@161 | 14 | N = 10 |
paul@161 | 15 | limit = 10 |
paul@161 | 16 | delay = 1 |
paul@161 | 17 | |
paul@161 | 18 | # Work function. |
paul@161 | 19 | |
paul@161 | 20 | def calculate(ch, i): |
paul@161 | 21 | |
paul@161 | 22 | """ |
paul@161 | 23 | A supposedly time-consuming calculation on 'i'. |
paul@161 | 24 | """ |
paul@161 | 25 | |
paul@161 | 26 | for j in range(0, N): |
paul@161 | 27 | #time.sleep(delay * random.random()) |
paul@161 | 28 | time.sleep(delay) |
paul@161 | 29 | ch.send((i, j, i * N + j)) |
paul@161 | 30 | |
paul@161 | 31 | # Main program. |
paul@161 | 32 | |
paul@161 | 33 | if __name__ == "__main__": |
paul@161 | 34 | |
paul@161 | 35 | t = time.time() |
paul@161 | 36 | |
paul@161 | 37 | # Initialise the communications queue with a limit on the number of |
paul@161 | 38 | # channels/processes. |
paul@161 | 39 | |
paul@161 | 40 | queue = pprocess.Queue(limit=limit, continuous=1) |
paul@161 | 41 | |
paul@161 | 42 | # Initialise an array. |
paul@161 | 43 | |
paul@161 | 44 | results = [0] * N * N |
paul@161 | 45 | |
paul@161 | 46 | # Manage the calculate function. |
paul@161 | 47 | |
paul@161 | 48 | calc = queue.manage(calculate) |
paul@161 | 49 | |
paul@161 | 50 | # Perform the work. |
paul@161 | 51 | |
paul@161 | 52 | print "Calculating..." |
paul@161 | 53 | for i in range(0, N): |
paul@161 | 54 | calc(i) |
paul@161 | 55 | |
paul@161 | 56 | # Store the results as they arrive. |
paul@161 | 57 | |
paul@161 | 58 | print "Finishing..." |
paul@161 | 59 | for i, j, result in queue: |
paul@161 | 60 | results[i*N+j] = result |
paul@161 | 61 | |
paul@161 | 62 | # Show the results. |
paul@161 | 63 | |
paul@161 | 64 | for i in range(0, N): |
paul@161 | 65 | for result in results[i*N:i*N+N]: |
paul@161 | 66 | print result, |
paul@161 | 67 | print |
paul@161 | 68 | |
paul@161 | 69 | print "Time taken:", time.time() - t |
paul@161 | 70 | |
paul@161 | 71 | # vim: tabstop=4 expandtab shiftwidth=4 |