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Subject: Re: [OMPI users] send and receive buffer the same on root
From: Tom Rosmond (rosmond_at_[hidden])
Date: 2010-09-16 17:00:59


The responsible programmer for this code has conceded the point and we
will be replacing all offending examples with the MPI_IN_PLACE solution.
Thanks for the input.

T. Rosmond

On Thu, 2010-09-16 at 13:56 -0700, Tim Prince wrote:
> On 9/16/2010 9:58 AM, David Zhang wrote:
> > It's compiler specific I think. I've done this with OpenMPI no
> > problem, however on one another cluster with ifort I've gotten error
> > messages about not using MPI_IN_PLACE. So I think if it compiles,
> > it should work fine.
> >
> > On Thu, Sep 16, 2010 at 10:01 AM, Tom Rosmond <rosmond_at_[hidden]>
> > wrote:
> > I am working with a Fortran 90 code with many MPI calls like
> > this:
> >
> > call mpi_gatherv(x,nsize(rank+1),
> >
> > mpi_real,x,nsize,nstep,mpi_real,root,mpi_comm_world,mstat)
> >
> Compiler can't affect what happens here (unless maybe you use x again
> somewhere). Maybe you mean MPI library? Intel MPI probably checks
> this at run time and issues an error.
> I've dealt with run-time errors (which surfaced along with an ifort
> upgrade) which caused silent failure (incorrect numerics) on openmpi
> but a fatal diagnostic from Intel MPI run-time, due to multiple uses
> of the same buffer. Moral: even if it works for you now with
> openmpi, you could be setting up for unexpected failure in the future.
> --
> Tim Prince
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