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Subject: Re: [OMPI users] Interaction between Intel and OpenMPI floating pointexceptions
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-04-08 07:02:01

On Apr 6, 2009, at 6:22 PM, Steve Lowder wrote:

> When I run the MPI version and set --mca opal_signal 6,7,11 the code
> doesn't abort on underflow. I'd like to know if I'm interpreting this
> behavior correctly, it appears that the mpi versus no mpi cases handle
> underflow differently. I'm assuming OpenMPI has a handler that
> processes
> the interrupts ahead of the Fortran RTL, stopping execution.
> Otherwise
> the Fortran RTL handler would just ignore the underflow. Do I sort of
> understand what is going on here? Is there another solution short of
> the --mca opal_signal switch?

You are correct; Open MPI inserts an FPE handler unless you tell it
to; your case is fairly special in that you *don't* want to see a
signal/stack trace when an FPE occurs. My $0.02 is that it is
probably easiest to always run with the opal_signal MCA param value
set to exclude the FPE handler, as you discovered.

Jeff Squyres
Cisco Systems