multiprocessing and Array problems

[Al Niessner]

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