如何一起使用多处理池和队列？

Question

我需要在超级计算机上执行~18000有点昂贵的计算，我正在试图弄清楚如何并行化代码。我有它主要使用multiprocessing.Process，但如果我做了超过350次计算，它会挂在.join（）步骤。

管理超级计算机的计算机科学家之一建议我使用multiprocessing.Pool而不是Process。

使用Process时，我会设置一个输出队列和一个进程列表，然后运行并加入这样的进程：

output = mp.Queue()
processes = [mp.Process(target=some_function,args=(x,output)) for x in some_array]
for p in processes:
    p.start()
for p in processes:
    p.join()

因为processes是一个列表，它是可迭代的，我可以在列表理解中使用output.get()来获得所有结果：

result = [output.get() for p in processes]

使用Pool时，相当于什么？如果Pool不可迭代，我如何获得其中每个进程的输出？

这是我尝试使用虚拟数据和虚拟计算：

import pandas as pd
import multiprocessing as mp

##dummy function
def predict(row,output):
    calc = [len(row.c1)**2,len(row.c2)**2]
    output.put([row.c1+' - '+row.c2,sum(calc)])

#dummy data
c = pd.DataFrame(data=[['a','bb'],['ccc','dddd'],['ee','fff'],['gg','hhhh'],['i','jjj']],columns=['c1','c2'])

if __name__ == '__main__':
    #output queue
    print('initializing output container...')
    output = mp.Manager().Queue()


    #pool of processes
    print('initializing and storing calculations...')
    pool = mp.Pool(processes=5)
    for i,row in c.iterrows(): #try some smaller subsets here
         pool.apply_async(predict,args=(row,output))

    #run processes and keep a counter-->I'm not sure what replaces this with Pool!
    #for p in processes:
    #    p.start()

    ##exit completed processes-->or this!
    #for p in processes:
    #    p.join()

    #pool.close() #is this right?
    #pool.join() #this?

#store each calculation
print('storing output of calculations...')
p = pd.DataFrame([output.get() for p in pool]) ## <-- this is where the code breaks because pool is not iterable
print(p)

我得到的输出是：

initializing output container...
initializing and storing calculations...
storing output of calculations...
Traceback (most recent call last):
  File "parallel_test.py", line 37, in <module>
    p = pd.DataFrame([output.get() for p in pool]) ## <-- this is where the code breaks because pool is not iterable
TypeError: 'Pool' object is not iterable

我想要的是p打印和看起来像：

        0   1
0      a - bb   5
1  ccc - dddd  25
2    ee - fff  13
3   gg - hhhh  20
4     i - jjj  10

如何从每次计算中获取输出而不是第一次？