Python multiprocessing hangs

Question

I am starting to learn multiprocessing in python, but have arrived to a point where my code just hangs. It is simply computing 1 000 000 factorial, using multithreading.

import multiprocessing def part(n): ret = 1 n_max = n + 9999 while n <= n_max: ret *= n n += 1 print "Part "+ str(n-1) + " complete" return ret def buildlist(n_max): n = 1 L = [] while n <= n_max: L.append(n) n += 10000 return L final = 1 ne = 0 if __name__ == '__main__': pool = multiprocessing.Pool() results = [pool.apply_async(part, (x,)) for x in buildlist(1000000)] for r in results: x = r.get() final *= x ne+= 1 print ne print final

I have included some print functions to try to diagnose where the code hangs, and it will print the string included in the part function 100 times, as expected. The "print ne" also works 100 times.

The problem is that final won't print, and the code doesn't complete.

How do I fix this problem?

Edit: Also, since this is being downvoted, could someone explain what I am doing wrong/why I am being downvoted?

1000!=8.2639316883×10^(5,565,708) There is nothing simple about it. — Daniel
– Daniel, Commented Jan 11, 2013 at 17:00
What I mean by that is that the code for doing factorials without multiprocessing is relatively simple code. — Patrick Poitras
– Patrick Poitras, Commented Jan 11, 2013 at 17:13

Armin Rigo · Accepted Answer · 2013-01-11 22:20:42Z

1

The program works fine --- until the print final. Then it spends a very large amount of time trying to print this number, which is seriously huge...

answered Jan 11, 2013 at 22:20

Armin Rigo

13.1k41 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Patrick Poitras Over a year ago

Yes, it finished computing after about 15 minutes when I let it run, following your comment.

Collectives™ on Stack Overflow

Python multiprocessing hangs

1 Answer 1

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Related