[Dune] Parallel alugrid gmsh reading

[Jö Fahlke]

Am Tue,  7. Jul 2015, 13:42:48 +0100 schrieb Andreas Dedner:
> Date: Tue, 7 Jul 2015 13:42:48 +0100
> From: Andreas Dedner <a.s.dedner at warwick.ac.uk>
> To: dune at dune-project.org
> Subject: Re: [Dune] Parallel alugrid gmsh reading
> 
> Hi Jake.
> Please always remember to add which version of the modules (in this case
> dune-grid and
> dune-alugrid) you are using because the answer could depend on that.
> What seems to be working fine is
> 
>   Dune::GridFactory<GridType> factory;
>   if( myRank == 0 )
>     Dune::GmshReader<GridType>::read(factory, gridfile, true, true );
>   GridType *gridPtr = factory.createGrid();
>   GridType& grid = *gridPtr ;
>   grid.loadBalance();
> 
> A small example code demonstrating the problem would help.
> Andreas

Hi Jake,

just a note: that means reading the grid sequentially, and then letting
ALUGrid distribute it.  With the old ALUGrid (1.52) you would run into memory
problems for sufficiently large grids and sufficiently many ranks.  I believe
that is better with the new ALUGrid, but if you experience similar problems,
get back to us and we can try to adapt the gmsh-to-alu workaround that I used
back then.

Regards,
Jö.

> On 07/07/15 13:19, Jake Langham wrote:
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> >Dear all,
> >
> >I am trying to read gmsh files in for a parallel ALUGrid code.
> >Browsing through the archives of this list, it seems this is an issue
> >that has come up a couple of times in the past - however I couldn't
> >find a definitive answer.
> >
> >My understanding is that the way to go about this is to read
> >everything in on rank 0, then call load balancing (for which, I use
> >zoltan).
> >
> >As has been pointed out on this list before
> >(http://lists.dune-project.org/pipermail/dune/2014-July/012921.html),
> >just calling the GmshReader on rank 0 doesn't work, since (possibly)
> >one just gets a bunch of grids that can't talk to each other.
> >
> >I have tried a bunch of different things in my code, mostly inspired
> >by the previous thread about this, but probably just don't understand
> >how Dune handles MPI well enough.
> >
> >Since this seems a common problem, perhaps someone has this working
> >now or at least has some more insight since the last time it was asked?
> >
> >(N.b. A while back I also tried dune-grid's gmsh-to-alu converter. It
> >did not seem to like my mesh files - but at that point I did not have
> >time to figure out what was wrong there. I'll take another look at
> >that soon.)
> >
> >Thanks,
> >
> >- -Jake Langham
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> 
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-- 
Jorrit (Jö) Fahlke, Institute for Computational und Applied Mathematics,
University of Münster, Orleans-Ring 10, D-48149 Münster
Tel: +49 251 83 35146 Fax: +49 251 83 32729

This is the first age that's paid much attention to the future, which
is a little ironic since we may not have one.
-- Arthur C Clarke
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