Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 1 | # |
| 2 | # Simple example which uses a pool of workers to carry out some tasks. |
| 3 | # |
| 4 | # Notice that the results will probably not come out of the output |
| 5 | # queue in the same in the same order as the corresponding tasks were |
| 6 | # put on the input queue. If it is important to get the results back |
| 7 | # in the original order then consider using `Pool.map()` or |
| 8 | # `Pool.imap()` (which will save on the amount of code needed anyway). |
| 9 | # |
Benjamin Peterson | 4469d0c | 2008-11-30 22:46:23 +0000 | [diff] [blame] | 10 | # Copyright (c) 2006-2008, R Oudkerk |
| 11 | # All rights reserved. |
| 12 | # |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 13 | |
| 14 | import time |
| 15 | import random |
| 16 | |
| 17 | from multiprocessing import Process, Queue, current_process, freeze_support |
| 18 | |
| 19 | # |
| 20 | # Function run by worker processes |
| 21 | # |
| 22 | |
| 23 | def worker(input, output): |
| 24 | for func, args in iter(input.get, 'STOP'): |
| 25 | result = calculate(func, args) |
| 26 | output.put(result) |
| 27 | |
| 28 | # |
| 29 | # Function used to calculate result |
| 30 | # |
| 31 | |
| 32 | def calculate(func, args): |
| 33 | result = func(*args) |
| 34 | return '%s says that %s%s = %s' % \ |
Benjamin Peterson | 58ea9fe | 2008-08-19 19:17:39 +0000 | [diff] [blame] | 35 | (current_process().name, func.__name__, args, result) |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 36 | |
| 37 | # |
| 38 | # Functions referenced by tasks |
| 39 | # |
| 40 | |
| 41 | def mul(a, b): |
| 42 | time.sleep(0.5*random.random()) |
| 43 | return a * b |
| 44 | |
| 45 | def plus(a, b): |
| 46 | time.sleep(0.5*random.random()) |
| 47 | return a + b |
| 48 | |
| 49 | # |
| 50 | # |
| 51 | # |
| 52 | |
| 53 | def test(): |
| 54 | NUMBER_OF_PROCESSES = 4 |
| 55 | TASKS1 = [(mul, (i, 7)) for i in range(20)] |
| 56 | TASKS2 = [(plus, (i, 8)) for i in range(10)] |
| 57 | |
| 58 | # Create queues |
| 59 | task_queue = Queue() |
| 60 | done_queue = Queue() |
| 61 | |
| 62 | # Submit tasks |
| 63 | for task in TASKS1: |
| 64 | task_queue.put(task) |
| 65 | |
| 66 | # Start worker processes |
| 67 | for i in range(NUMBER_OF_PROCESSES): |
| 68 | Process(target=worker, args=(task_queue, done_queue)).start() |
| 69 | |
| 70 | # Get and print results |
Christian Heimes | aae1b70 | 2008-11-28 11:23:26 +0000 | [diff] [blame] | 71 | print('Unordered results:') |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 72 | for i in range(len(TASKS1)): |
Christian Heimes | aae1b70 | 2008-11-28 11:23:26 +0000 | [diff] [blame] | 73 | print('\t', done_queue.get()) |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 74 | |
| 75 | # Add more tasks using `put()` |
| 76 | for task in TASKS2: |
| 77 | task_queue.put(task) |
| 78 | |
| 79 | # Get and print some more results |
| 80 | for i in range(len(TASKS2)): |
Christian Heimes | aae1b70 | 2008-11-28 11:23:26 +0000 | [diff] [blame] | 81 | print('\t', done_queue.get()) |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 82 | |
| 83 | # Tell child processes to stop |
| 84 | for i in range(NUMBER_OF_PROCESSES): |
| 85 | task_queue.put('STOP') |
| 86 | |
| 87 | |
| 88 | if __name__ == '__main__': |
| 89 | freeze_support() |
| 90 | test() |