I have been using the multiprocessing module to do network analysis's 'find closest facility' task for number of incidents in ArcMap 10.2.1.
I have written python script which works fine if I run it in IDLE. I see all my cores max out in Task Manager and the code completes without error.
Now if I executes this script as a Script Tool in ArcToolbox it throws a following error
"Could not find file: from multiprocessing.forking import main; main().mxd"
As per ESRI Blogs, I regularly see that the script has to be "run out of process". So I unchecked the check box "run python in process" in the script properties dialog, and run the script tool. But the script tool starts execution and complete it without any processing.