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Subject: Re: [OMPI users] MPI_Allreduce on local machine
From: Terry Frankcombe (terry_at_[hidden])
Date: 2010-07-27 23:44:54


On Tue, 2010-07-27 at 16:19 -0400, Gus Correa wrote:
> Hi Hugo, David, Jeff, Terry, Anton, list
>
> I suppose maybe we're guessing that somehow on Hugo's iMac
> MPI_DOUBLE_PRECISION may not have as many bytes as dp = kind(1.d0),
> hence the segmentation fault on MPI_Allreduce.
>
> Question:
>
> Is there a simple way to check the number of bytes associated to each
> MPI basic type of OpenMPI on a specific machine (or machine+compiler)?
>
> Something that would come out easily, say, from ompi_info?

bit_size() will give you the integer size. For reals, digits() will
give you a hint, but the Fortran real data model is designed to not tie
you to a particular representation (my interpretation), so there's no
language feature to give a simple word size.