[Numpy-discussion] numpy.random and multiprocessing

Michael Gilbert michael.s.gilbert@gmail....
Thu Dec 11 11:10:03 CST 2008


> Exactly, change task_helper.py to
>
> ----
> import numpy as np
>
> def task(x):
>     import os
>     print "Hi, I'm", os.getpid()
>     return np.random.random(x)
> ----
>
> and note the output
>
> ----
> Hi, I'm 16197
> Hi, I'm 16198
> Hi, I'm 16199
> Hi, I'm 16199
> [ 0.58175647  0.16293922  0.30488182  0.67367263]
> [ 0.58175647  0.16293922  0.30488182  0.67367263]
> [ 0.58175647  0.16293922  0.30488182  0.67367263]
> [ 0.59574921  0.61554857  0.06155764  0.75352295]

Shouldn't numpy (and/or multiprocessing) be smart enough to prevent
this kind of error?  A simple enough solution would be to also include
the process id as part of the seed since it appears that the problem
only occurs when you have different processes/threads accessing the
random number generator at the same time.

Regards,
Mike


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