Ethan Welty <ethan.we...@gmail.com> added the comment:
@ronaldoussoren: The order of the imports made no difference. Even with the
call at the top, I got endless errors with both 'spawn' and 'forkserver', with
or without importing a graphics backend. Only 'fork' works, and only if a
graphics package is not imported.
** HOWEVER **
Setting method='spawn' or 'forkserver' and force=True at top, or calling
multiprocessing.set_start_method in __main__ does work (when run as scripts
from command line). It's a shame to have to give up the convenience of 'fork',
but this is a start.
```
import multiprocessing
multiprocessing.set_start_method("spawn", force=True)
import numpy as np
# import _tkinter
def parallel_matmul(x):
R = np.random.randn(3, 3)
return np.matmul(R, x)
if __name__ == '__main__':
# multiprocessing.set_start_method("spawn", force=False)
pool = multiprocessing.Pool(4)
results = pool.map(parallel_matmul, [np.random.randn(3, 5000) for i in
range(2)])
```
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue33111>
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