[Dune] Contribution to CollectiveCommunication

[Markus Blatt]

Hi,

On Thu, Jan 22, 2015 at 09:50:49AM +0100, Aleksejs Fomins wrote:
> Dear Dune,
> 
> Following our discussions on POD communication, I have written a small
> utility, which might find its place among CollectiveCommunication
> methods if people want it. The motivation is that there are numerous
> gather and scatter methods in there, but no wrapper for MPI_Alltoallv,
> as far as I can tell.
> 

probably because nobody needed it yet.

> [... MPI]
> For example, if process 1 would like to send
> 2 elements to process 0
> 3 elements to process 1 (self)
> 5 elements to process 2
> then "in" would have length 10, and lengthIn={2,3,5} on process 1
> 

This question might be really stupid, but up until now I was under the
impression that you are working on implementing the communication
interface for curvilinear-grid. Where would you need such a
functionality for this?

Just to be sure (ignore it if I am pointing out the obvious):
Please note that from outside it might seem as  the communication in
the grid interface is sending from  all to all processors. But for
large numbers of processors there is alway a quite small number of
processors where a process might send to or receive from. I am sure
that you agree that MPI_Alltoallv is not the weapon of choice here.

Markus


-- 
Do you need more support with DUNE or HPC in general? 

Dr. Markus Blatt - HPC-Simulation-Software & Services http://www.dr-blatt.de
Hans-Bunte-Str. 8-10, 69123 Heidelberg, Germany
Tel.: +49 (0) 160 97590858
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