[Numpy-discussion] Annoyance of memap rray with multiprocessing.Pool.applay_async

[Nadav Horesh]

The following script generate the following error on every loop iteration in the function average:

Exception AttributeError: AttributeError("'NoneType' object has no attribute 'tell'",) in <bound method memmap.__del__ of memmap(xxxxxx)> ignored

where xxxxxx is a scalar (the array sum).

I get this error with numpy1.4 on a linux64 (dual core) machine. A winXP/Pentium4 with 2GB Ram could not run it since it explode the memory.

 Any idea what is the origin on the error (my interset is the linux box)?

BTW if in the function average the 2nd line is commented and the 3rd line is uncommented I get no error on linux, but the win32 problem pertains.

----------------------------------------------------------------
import numpy as N
import multiprocessing as MP
import sys

try:
    count = int(sys.argv[1])
except:
    count = 4
filename = '%dx100x100_int32.dat' % count

def average(cube):
   return [plane.mean() for plane in cube]
#    return [N.asarray(plane).mean() for plane in cube]


data = N.memmap(filename, dtype=N.int32, shape=(count,100,100))

pool = MP.Pool(processes=1)

job = pool.apply_async(average, [data,])
print job.get()
import numpy as N
import multiprocessing as MP

count = 4
filename = '%dx100x100_int32.dat' % count

def average(cube):
   return [plane.mean() for plane in cube]
#    return [N.asarray(plane).mean() for plane in cube]


data = N.memmap(filename, dtype=N.int32, shape=(count,100,100))

pool = MP.Pool(processes=1)

job = pool.apply_async(average, [data,])
print job.get()
----------------------------------------------------------------

   Nadav