QVMError when multiprocessing

Hi,

I would like to parallelize running of quantum circuits to get faster estimates of their gradients. One library that makes multiprocessing pretty painless is ray.

When I create the workers for running multiple circuits in parallel, I get the following error pyquil.api._errors.QVMError: Unhandled memory fault at #x0

There is a useful debugging feature ray provides to serialize the computation, at which point the error no longer occurs. The QVM doesn’t crash nor does it write any error messages that indicate some failure. I am wondering if there is perhaps simply an issue with throughput and maybe the request got dropped?

Thanks, Vincent

[notmgsk]

@vipasu I’m doing some testing for these changes (making sure they fix the above) and then I’ll update the packages. I’ll post a message here when I’ve finished.

[notmgsk]

Your above code now runs to completion. If you have docker installed, you can test these changes by running the following command: ~docker run -p 5555:5555 -it rigetti/quilc:edge -R -p 5555 -Pjdrtf2 --compute-gate-volume --without-pretty-printing~ docker run -p 5000:5000 -it rigetti/qvm:edge -S and then your script above should run using this as the QVM.