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Subject: Re: [OMPI users] send and receive buffer the same on root
From: Tim Prince (n8tm_at_[hidden])
Date: 2010-09-16 16:56:36


  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]
> <mailto: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