Here is an update.
def subproc (i):
print ("From subprocess " + str(i))
print (b[:])
return
if __name__ == "__main__":
nproc = 3
print ("\nBuilding the array for the second computation.")
b = multiprocessing.Array (ctypes.c_double, nproc*nproc, lock=False)
print ("\nSending the task across to see what happens.")
pool = multiprocessing.Pool(nproc)
for i in range(nproc): pool.apply_async (subproc, kwds={'i':i})
pool.close()
pool.join()
pass
Does work. It is not what I need though. I need to be able to pass b as
an argument. The reason is that I create some of these in a loop and
they are not in a global space nor are they know prior to creating the
pool.
On Thu, 2012-04-12 at 11:15 -0700, Al Niessner wrote:
> I am not subscribed to these lists but I do check them occasionally and
> will check them more frequently looking for a response.
>
> I am getting a pickling error that I do not understand. It seems the
> shared arrays that I create cannot be pickled. Makes the
> multiprocessing.Array fairly useless if it cannot be pickled. Hence, I
> am guessing that I am doing something wrong and would like some help
> spotting it.
>
> This is basically a cut and paste from the examples in the
> documentation:
>
> import ctypes
> import multiprocessing
>
> def subproc (a, i):
> print ("From subprocess " + str(i))
> print (a[:])
> return
>
> if __name__ == "__main__":
> nproc = 3
> print ("\nBuilding the array for the second computation.")
> b = multiprocessing.Array (ctypes.c_double, nproc*nproc, lock=False)
>
> print ("\nSending the task across to see what happens.")
> pool = multiprocessing.Pool(nproc)
> for i in range(nproc): pool.apply_async (subproc, kwds={'a':b,
> 'i':i})
> pool.close()
> pool.join()
> pass
>
> Whether I run it on 2.6, 2.7, or 3.2 I get the same error.
>
> Exception in thread Thread-1:
> Traceback (most recent call last):
> File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner
> self.run()
> File "/usr/lib/python2.6/threading.py", line 484, in run
> self.__target(*self.__args, **self.__kwargs)
> File "/usr/lib/python2.6/multiprocessing/pool.py", line 225, in
> _handle_tasks
> put(task)
> PicklingError: Can't pickle <class
> 'multiprocessing.sharedctypes.c_double_Array_9'>: attribute lookup
> multiprocessing.sharedctypes.c_double_Array_9 failed
>
>
> Anyone want to take a stab as to why this error message is being
> generated? Again I have tried python 2.6.7, 2.7.2+, and 3.2.2.
>
> Thanks for any and all help in advance.
>
--
Al Niessner
I have never found the companion that was so companionable as solitude.
- From Walden by Henry David Thoreau
The universe is indifferent, and life is brutal; however, it is man's
choice of behavior that makes them malevolent rather than benevolent.
Some will fall in love with life and drink it from a fountain
That is pouring like an avalanche coming down the mountain.
- From the song Pepper by the Butthole Surfers
--
http://mail.python.org/mailman/listinfo/python-list
