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[英]Multiprocessing in Python: Parallelize a for loop to fill a Numpy array
[英]Trying to use multiprocessing to fill an array in python
我有這樣的代碼
x = 3;
y = 3;
z = 10;
ar = np.zeros((x,y,z))
from multiprocessing import Process, Pool
para = []
process = []
def local_func(section):
print "section %s" % str(section)
ar[2,2,section] = 255
print "value set %d", ar[2,2,section]
pool = Pool(1)
run_list = range(0,10)
list_of_results = pool.map(local_func, run_list)
print ar
ar中的值未通過多線程更改,這可能是什么問題?
謝謝
您在這里使用多個進程,而不是多個線程。 因此, local_func
每個實例local_func
獲得其自己的ar
單獨副本。 您可以使用自定義Manager
來創建共享的numpy數組,您可以將其傳遞給每個子進程並獲得所需的結果:
import numpy as np
from functools import partial
from multiprocessing import Process, Pool
import multiprocessing.managers
x = 3;
y = 3;
z = 10;
class MyManager(multiprocessing.managers.BaseManager):
pass
MyManager.register('np_zeros', np.zeros, multiprocessing.managers.ArrayProxy)
para = []
process = []
def local_func(ar, section):
print "section %s" % str(section)
ar[2,2,section] = 255
print "value set %d", ar[2,2,section]
if __name__ == "__main__":
m = MyManager()
m.start()
ar = m.np_zeros((x,y,z))
pool = Pool(1)
run_list = range(0,10)
func = partial(local_func, ar)
list_of_results = pool.map(func, run_list)
print ar
好吧,多線程和多處理是不同的事情。
使用多線程線程共享對同一陣列的訪問。
通過多處理,每個進程都有自己的數組副本。
multiprocessing.Pool
是一個進程池,而不是線程池。
如果需要線程池,請使用multiprocess.pool.ThreadPool
:
更換:
from multiprocessing import Pool
與:
from multiprocessing.pool import ThreadPool as Pool
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