[Dune-devel] [Dune-Commit] [Commit] dune-grid - f6165ab: [yaspgrid, bugfix] Use canonical communicator type for non-MPI case

[Martin Nolte]

Hi Dominic,

you are right: For ages we have been passing the grid as template argument to 
CollectiveCommunication, if MPI was not desired. During that time, 
FakeMPIHelper::MPICommunicator was defined as int (which can coincide with MPIComm).

A few years ago, I took the liberty of introducing a type that will never 
coincide with MPIComm. This type is called Dune::No_Comm (looking a bit like 
MPI_Comm on purpose). It is, of course, an empty class to be used as a tag. This 
type is used for FakeMPIHelper::MPICommunicator (so using Dune::No_Comm would 
give the same result).

In view of the recent idea to pass the collective communication to the 
backup-restore facilities on restore, it might be good if all grids used either 
CollectiveCommunication< MPI_Comm > or CollectiveCommunication< No_Comm >.

Best,

Martin

On 10/03/2014 11:54 AM, Dominic Kempf wrote:
> Actually, that is nothing new at all. Its been that way "forever".
>
> In the sequential case, one wants to use the default CollectiveCommunication (as
> defined in collectivecommunication.hh). To get that default implementation, a
> template parameter is to be given, that ensures that there is no specialization,
> that actually does something. Yasp uses its own name to do that. Any other name
> other than MPI_Comm would do.
>
> I will have a look into vtktest to check what is wrong there.
>
>
> On Fri, Oct 3, 2014 at 11:23 AM, Markus Blatt <markus at dr-blatt.de
> <mailto:markus at dr-blatt.de>> wrote:
>
>     New commit, appeared at Fri Oct  3 11:23:45 2014 +0200
>     as part of the following ref changes:
>
>          branch refs/heads/master    updated from a3ff58a -> f6165ab
>
>     Browsable version:
>     http://cgit.dune-project.org/repositories/dune-grid/commit/?id=f6165aba501863dce958719ebbc2103ae8a646da
>
>     ======================================================================
>
>     commit f6165aba501863dce958719ebbc2103ae8a646da
>     Author: Markus Blatt <markus at dr-blatt.de <mailto:markus at dr-blatt.de>>
>     Date:   Fri Oct 3 11:23:02 2014 +0200
>
>          [yaspgrid,bugfix] Use canonical communicator type for non-MPI case
>
>          If people write programs the DUNE way then they will end up with
>          Dune::FakeMPIHelper::MPICommunicator as their communicator type.
>          Unfortunately Yaspgrid uses YaspGrid<dim, Coordinates> which is far
>          from being inituitive and broke vtktest. This patch resorts to using
>          the canonical choice, Dune::FakeMPIHelper::MPICommunicator, and fixes
>          the test.
>
>       dune/grid/yaspgrid.hh | 4 ++--
>       1 file changed, 2 insertions(+), 2 deletions(-)
>
>
>
>     diff --git a/dune/grid/yaspgrid.hh b/dune/grid/yaspgrid.hh
>     index f54fe6f..832ab7c 100644
>     --- a/dune/grid/yaspgrid.hh
>     +++ b/dune/grid/yaspgrid.hh
>     @@ -89,7 +89,7 @@ namespace Dune {
>       #if HAVE_MPI
>           typedef CollectiveCommunication<MPI_Comm> CCType;
>       #else
>     -    typedef CollectiveCommunication<Dune::YaspGrid<dim, Coordinates> > CCType;
>     +    typedef CollectiveCommunication<FakeMPIHelper::MPICommunicator> CCType;
>       #endif
>
>           typedef GridTraits<dim,                                     //
>     dimension of the grid
>     @@ -167,7 +167,7 @@ namespace Dune {
>       #ifdef HAVE_MPI
>           typedef CollectiveCommunication<MPI_Comm> CollectiveCommunicationType;
>       #else
>     -    typedef CollectiveCommunication<YaspGrid<dim, Coordinates> >
>     CollectiveCommunicationType;
>     +    typedef CollectiveCommunication<FakeMPIHelper::MPICommunicator>
>     CollectiveCommunicationType;
>       #endif
>
>       #ifndef DOXYGEN
>
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-- 
Dr. Martin Nolte <nolte at mathematik.uni-freiburg.de>

Universität Freiburg                                   phone: +49-761-203-5630
Abteilung für angewandte Mathematik                    fax:   +49-761-203-5632
Hermann-Herder-Straße 10
79104 Freiburg, Germany