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Subject: Re: [OMPI users] "An error occurred in MPI_Recv" with more than 2 CPU
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-05-27 13:35:49


George Bosilca wrote:

> This is a problem of numerical stability, and there is no solution
> for such a problem in MPI. Usually, preconditioning the input
> matrix improve the numerical stability.

At the level of this particular e-mail thread, the issue seems to me to
be different. Results are added together in some arbitrary order and
there are variations on order of 10^-10. This is not an issue of
numerical stability, but just of bitwise floating-point reproducibility.

And, given that one could fix the order (by using explicit source
processes instead of MPI_ANY_SOURCE), one could "fix" this particular
problem in MPI.

Anyhow, I'm just picking nits here.