Traceback when using multiprocessing, less than helpful?

Chris Angelico rosuav at
Thu Nov 21 18:24:33 CET 2013

On Fri, Nov 22, 2013 at 4:01 AM, John Ladasky
<john_ladasky at> wrote:
> Here is the end of the traceback, starting with the last line of my code: "result =, bundles)".  After that, I'm into Python itself.
>   File ".../", line 81, in evaluate
>     result =, bundles)
>   File "/usr/lib/python3.3/multiprocessing/", line 228, in map
>     return self._map_async(func, iterable, mapstar, chunksize).get()
>   File "/usr/lib/python3.3/multiprocessing/", line 564, in get
>     raise self._value
> ValueError: operands could not be broadcast together with shapes (1,3) (4)
> Notice that no line of numpy appears in the traceback?  Still, there are three things that make me think that this error is coming from numpy.

Hmm. This looks like a possible need for the 'raise from' syntax. I
just checked multiprocessing/ from 3.4 alpha, and it has much
what you're seeing there, in the definition of AsyncResult (of which
MapResult is a subclass). The question is, though, how well does the
information traverse the process boundary?


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