Python多處理並不像預測的那樣工作

我在網上發現了這個代碼，預測的結果應該顯示當前正在處理的進程名稱，但是當我運行代碼時，它只給出結果而不是名稱。我運行Windows 7 Python 2.7.3。Python多處理並不像預測的那樣工作

代碼：

import multiprocessing 

def do_calculation(data): 
    return data * 2 

def start_process(): 
    print 'Starting', multiprocessing.current_process().name 

if __name__ == '__main__': 
    inputs = list(range(10)) 
    print 'Input :', inputs 

    builtin_outputs = map(do_calculation, inputs) 
    print 'Built-in:', builtin_outputs 

    pool_size = multiprocessing.cpu_count() * 2 
    pool = multiprocessing.Pool(processes=pool_size, 
           initializer=start_process, 
           ) 
    pool_outputs = pool.map(do_calculation, inputs) 
    pool.close() # no more tasks 
    pool.join() # wrap up current tasks 

    print 'Pool :', pool_outputs

預期結果：

$ python multiprocessing_pool.py 

Input : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 
Built-in: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] 
Starting PoolWorker-11 
Starting PoolWorker-12 
Starting PoolWorker-13 
Starting PoolWorker-14 
Starting PoolWorker-15 
Starting PoolWorker-16 
Starting PoolWorker-1 
Starting PoolWorker-2 
Starting PoolWorker-3 
Starting PoolWorker-4 
Starting PoolWorker-5 
Starting PoolWorker-8 
Starting PoolWorker-9 
Starting PoolWorker-6 
Starting PoolWorker-10 
Starting PoolWorker-7 
Pool : [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

來源

2013-07-10 user2569466

你爲什麼期待這種情況發生？你粘貼的輸出看起來像你顯示的代碼的正確行爲。 – Gian

我唯一的猜測是你實際上希望你的'do_calculation'主體看起來像這樣：'return（data * 2，multiprocessing.current_process（）。name）'它返回'data * 2'和工作者名字一個元組。 – sberry

你試過檢查multiprocessing.cpu_count（）返回什麼嗎？ – fsw

如果我運行在一個控制檯下面的代碼，而不是IDLE（我一直使用PyCharm後要回）：

from multiprocessing import * 

def main(): 
    data = list(range(10)) 
    print('Data:', data) 

    result = list(map(calculate, data)) 
    print('Map: ', result) 

    pool = Pool(cpu_count() * 2, initialize) 
    result = pool.map(calculate, data, 1) 
    pool.close() 
    pool.join() 

    print('Pool:', result) 

def calculate(number): 
    return number * 2 

def initialize(): 
    print('Starting', current_process().name) 

if __name__ == '__main__': 
    main()

C:\Users\schappell\Desktop>stack_overflow.py 
Data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 
Map: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] 
Starting PoolWorker-1 
Starting PoolWorker-13 
Starting PoolWorker-2 
Starting PoolWorker-3 
Starting PoolWorker-8 
Starting PoolWorker-5 
Starting PoolWorker-14 
Starting PoolWorker-16 
Starting PoolWorker-15 
Starting PoolWorker-12 
Starting PoolWorker-6 
Starting PoolWorker-9 
Starting PoolWorker-4 
Starting PoolWorker-10 
Starting PoolWorker-7 
Starting PoolWorker-11 
Pool: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] 

C:\Users\schappell\Desktop>

作爲一個側面說明，嘗試（與不time.sleep註釋掉）運行下面的代碼來代替：打印到控制檯屏幕爲您的預期（與PoolWorkers隨機順序）以下：

from multiprocessing import * 
import time 

def main(): 
    data = list(range(10)) 
    print('Data:', data) 
    print('Map: ', list(map(calculate, data))) 
    pool = Pool(cpu_count() * 2, initialize) 
## time.sleep(1) 
    print('Pool:', pool.map(calculate, data, 1)) 
    pool.close() 
    pool.join() 

def calculate(number): 
    return number * 2 

def initialize(): 
    print('Starting', current_process().name) 

if __name__ == '__main__': 
    main()

沒有睡覺，你可能會得到這樣的事情（顯示你的游泳池還沒有完全建立至今）：

C:\Users\schappell\Desktop>stack_overflow.py 
Data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 
Map: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] 
Starting PoolWorker-2 
Pool: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] 
Starting PoolWorker-1 
Starting PoolWorker-10 
Starting PoolWorker-9 
Starting PoolWorker-6 
Starting PoolWorker-14 
Starting PoolWorker-13 
Starting PoolWorker-5 
Starting PoolWorker-4 
Starting PoolWorker-3 
Starting PoolWorker-8 
Starting PoolWorker-11 
Starting PoolWorker-12 
Starting PoolWorker-16 
Starting PoolWorker-7 
Starting PoolWorker-15 

C:\Users\schappell\Desktop>

來源

2013-07-10 19:05:44

Python多處理並不像預測的那樣工作

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