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Subject: Re: [OMPI users] MPI_Gatherv and 0 size?
From: George Bosilca (bosilca_at_[hidden])
Date: 2009-02-23 15:28:32


The only restriction the MPI standard impose on the sendcounts and
recvcounts arrays is that the values be non-negative, so zero is a
legal value.

I don't really understand your second question. Where do you want to
use NULL ? In general NULL is not accepted in MPI as an argument for
any function ...

   george.

On Feb 23, 2009, at 02:55 , jody wrote:

> Hi
> I have an application in which various processes create different
> amounts of data (including no data at all).
> I have found that MPI_Scatterv and MPI_Gatherv do work with arrays
> sendcounts or receivecounts containing zeros.
>
> Since i didn't find the case of 0 sizes in the descriptions
> of these functions in the MPI reference, i wondered whether
> the use of zeroes is legal or if i was simply lucky that it worked.
>
> An other point: currently i use 1-sized buffers in the
> case of a 0-sized data transfer.
> Now if 0-sized data transfer is legal, would it be ok to
> pass NULL for the buffer?
>
> Thank You
> Jody
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