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Thank you for the clarification. Some comments below:</div>
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<div class="">On 5 Jul 2019, at 14:38, Jö Fahlke <<a href="mailto:jorrit.fahlke@wwu.de" class="">jorrit.fahlke@wwu.de</a>> wrote:</div>
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<div class="">Am Fr, 5. Jul 2019, 12:28:51 +0000 schrieb Guichard, Roland:<br class="">
<blockquote type="cite" class="">I see thanks.<br class="">
A quick question though, does it mean that there are several MPI initializations possible within Dune and the communicator that needs to be passed to the GridPtr (from dune-fem) is responsible for handling the mesh in parallel ?<br class="">
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MPI_Init is only ever called once.<br class="">
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<div>Yes, but potentially through multiple ways. I mean by this that for instance the Dune::Fem::MPIManager::initialize( argc, argv ) implicitly calls the <span class="n">MPIHelper</span><span class="o">::</span><span class="n">instance</span><span class="p">(</span>
<span class="n">argc</span><span class="p">,</span> <span class="n">argv</span> <span class="p">
). I understand that managers are wrappers around the MPIHelper one. However what I don’t quiet get so far is that, in the code, MPI ranks and size are retrieved using direct MPI calls:</span></div>
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<div>MPI_Comm_rank(MPI_COMM_WORLD, &myRank);</div>
<div>MPI_Comm_size(MPI_COMM_WORLD, &numProcs);</div>
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<div>But since the managers provide that functionality I don’t see the point in doing this. Ideally and for readability, you would access anything you need through a single manager. And this also applies to the communicator. </div>
<div>But that is merely my opinion.</div>
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<div class="">Though it is up to the grid manager implementation which MPI communicators are<br class="">
supported. Some managers may implicitly assume MPI_COMM_WORLD, others may not<br class="">
support MPI at all (which is implicitly equivalent to MPI_COMM_SELF).<br class="">
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<div>Hm, do I need to understand managers in a larger scope that MPI only then ? </div>
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<div class="">For yet others it may be possible to specify the communicator when<br class="">
constructing the grid. So if you obtained that communicator by splitting<br class="">
MPI_COMM_WORLD into two subsets of nodes, you will end up with two independent<br class="">
grids, each operating within one of the subsets.<br class="">
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<div>OK got that one.</div>
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Regards,<br class="">
Jö.<br class="">
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-- <br class="">
Jorrit (Jö) Fahlke, Institute for Computational und Applied Mathematics,<br class="">
University of Münster, Orleans-Ring 10, D-48149 Münster<br class="">
Tel: +49 251 83 35146 Fax: +49 251 83 32729<br class="">
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This message is protected by DoubleROT13 encryption<br class="">
Attempting to decode it violates the DMCA/WIPO acts<br class="">
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