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
--
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