[petsc-dev] Swarm tag error

[Dave May]

On Mon, 21 Nov 2022 at 12:37, 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?
>


I think it should be possible to use the adjacency graph associated with
the neighbour ranks which is defined within
_DMSwarmDataExCompleteCommunicationMap()
in the Mat object.

If Intel MPI cannot support tags greater than 1024, the proposition above
is going to be of limited value.
A job with 100 MPI ranks, with subdomains which each have 11 neighbour
ranks will exceed 1024.


>
>   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/>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20221123/deb1e062/attachment.html>