An example of how to use multiprocessing from within Maya, by actually running it as a subprocess and communicating back the results.

maya_script_editor.py

"""
This code can be run from a Maya script editor
"""
import subprocess
import cPickle

print 'This value below should be a 1000:'

p = subprocess.Popen(["/path/to/multi_test.py", "-po"], stdout=subprocess.PIPE)
result = cPickle.load(p.stdout)

print result

multi_test.py

#!/usr/bin/env python 

import multiprocessing
from time import time
import cPickle
import sys

## Simple func to eat up cpu power.
def whileFunc(z):
    while z < 100000:
        z += 1 
    return z

if __name__ == "__main__":
    ## Get current time 
    currtime = time()

    ## How often to run (just a test value)
    N = 1000
    ## Just a list with 1s 
    myList = [1]*N

    nrOfProcessors = multiprocessing.cpu_count() 

    ## Set our pool of processors 
    po = multiprocessing.Pool(nrOfProcessors)
    
    ## create the threads 
    res = po.map_async(whileFunc, myList)
    
    ## If we pass a -po flag, pickle the output and write it out    
    if '-po' in sys.argv[1:]:
        results = len(res.get())
        cPickle.dump(results, sys.stdout, -1)
        sys.stdout.flush()
        sys.exit(0)

    print 'This value below should be a 1000:'
    print len(res.get())
    print 'time elapsed:', time() - currtime

@jf20 / @akashCGI

I don't have a windows box to test, but it looks like it is caused by the translation of my linux/osx code to a Windows command, but not accounting for the difference that windows actually needs the path to the python executable as the first arguments.

Untested, but you might need to do something like

import sys

p = subprocess.Popen([sys.executable, "C:/test/multi_test.py", "-po"], stdout=subprocess.PIPE)