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Subject: Re: [OMPI devel] Warning on fork() disappears if I use MPI threads!!
From: N.M. Maclaren (nmm1_at_[hidden])
Date: 2010-11-29 14:30:09


On Nov 29 2010, George Bosilca wrote:
>
> If your code doesn't exactly what is described in the code snippet
> attached to your previous email, then you can safely ignore the warning.
> In fact, any fork done prior to the communication is a non-issue, but it
> is difficult to identify. Therefore, we output the warning as soon as we
> detect a fork after MPI_Init.

USUALLY a non-issue.

> You can find more information about the usage of fork in Open MPI at
> http://www.open-mpi.de/faq/?category=tuning#fork-warning

Yes. It says about as much as can be said, except between consenting
geeks in private! Well, I suppose that this mailing list counts :-)

I have had trouble with systems that sent signals to process groups
and/or all processes with a particular controlling terminal, and even
operating system 'super groups', where the location of the fork won't
save you. I can't see how to describe that issue in terms that make
sense to most users.

Regards,
Nick Maclaren.