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如何在python numpy中并行化求和计算?

如何在python numpy中并行化求和计算?

我想出了如何使用多处理,apply_async和回调将数组的总和并行化,所以我将其发布在这里供其他人使用。我使用的示例页面并行的Python的总和回调类,虽然我没有真正使用该程序包实施。不过,它给了我使用回调的想法。这是我最终使用的简化代码,它可以完成我想要的操作。

import multiprocessing
import numpy as np
import thread

class Sum: #again, this class is from ParallelPython's example code (I modified for an array and added comments)
    def __init__(self):
        self.value = np.zeros((1,512*512)) #this is the initialization of the sum
        self.lock = thread.allocate_lock()
        self.count = 0

    def add(self,value):
        self.count += 1
        self.lock.acquire() #lock so sum is correct if two processes return at same time
        self.value += value #the actual summation
        self.lock.release()

def computation(index):
    array1 = np.ones((1,512*512))*index #this is where the array-returning computation goes
    return array1

def summers(num_iters):
    pool = multiprocessing.Pool(processes=8)

    sumArr = Sum() #create an instance of callback class and zero the sum
    for index in range(num_iters):
        singlepoolresult = pool.apply_async(computation,(index,),callback=sumArr.add)

    pool.close()
    pool.join() #waits for all the processes to finish

    return sumArr.value

我还可以使用并行映射来完成此工作,这在另一个答案中建议。我已经尝试过了,但是没有正确实现。两种方法都有效,我认为这个答案很好地说明了使用哪种方法(映射或apply.async)的问题。对于地图版本,您无需定义Sum类,summers函数将变为

def summers(num_iters):
    pool = multiprocessing.Pool(processes=8)

    outputArr = np.zeros((num_iters,1,512*512)) #you wouldn't have to initialize these
    sumArr = np.zeros((1,512*512))              #but I do to make sure I have the memory

    outputArr = np.array(pool.map(computation, range(num_iters)))
    sumArr = outputArr.sum(0)

    pool.close() #not sure if this is still needed since map waits for all iterations

    return sumArr
python 2022/1/1 18:39:01 有248人围观

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