[petsc-dev] Swarm tag error

Junchao Zhang junchao.zhang at gmail.com
Tue Nov 22 23:23:12 CST 2022

I don't understand why you need so many tags.  Is the communication pattern
actually MPI_Alltoallv, but you implemented it in MPI_Send/Recv?

--Junchao Zhang

On Mon, Nov 21, 2022 at 2:37 PM Matthew Knepley <knepley at gmail.com> wrote:

> In data_ex.c, Swarm uses a distinct tag for each pair of processes. If the
> number of processes exceeds 1024, there are > 1024^2 tags which exceeds
> MPI_TAG_UB on Intel MPI.
> My solution is going to be to use that process pair number modulo
> MPI_TAG_UB. Does anyone have a slicker suggestion?
>   Thanks,
>       Matt
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
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