[Dune] problem with subsampling

[Christoph Grüninger]

Hi Arya,
do you use dune-grid directly or through an abstraction level like
PDELab or dune-FEM? From PDELab it works for me, so in general it is
working:

> StaggeredQ0DGF staggeredQ0DGF(vsub, x);
> P0DGF p0dgf(psub, x);
> Dune::SubsamplingVTKWriter<GV> vtkwriter(gv, 1);
> vtkwriter.addCellData(new Dune::PDELab::VTKGridFunctionAdapter<P0DGF>(p0dgf, "pressure"));
> vtkwriter.addCellData(new Dune::PDELab::VTKGridFunctionAdapter<StaggeredQ0DGF>(staggeredQ0DGF, "velocity"));
> sprintf(fname, "test_k-%04d", gridCells);
> vtkwriter.write(fname, Dune::VTK::ascii);

Maybe have a look at testsgrid in dune/grid/io/file/dgfparser/test.
With these changes the subsampling writer seems to work (at least the
output was not the same) for the grid, there was no data attached:

--- a/dune/grid/io/file/dgfparser/test/main.cc
+++ b/dune/grid/io/file/dgfparser/test/main.cc
@@ -51,12 +51,12 @@ void display ( const std::string &name,
     disp.display();
   }
 #endif // #if HAVE_GRAPE
-  VTKWriter<GridView> vtkWriter(view);
-  // SubsamplingVTKWriter<GridView> vtkWriter(view,6);
+  //VTKWriter<GridView> vtkWriter(view);
+  SubsamplingVTKWriter<GridView> vtkWriter(view,3);
   if( nofElParams + nofVtxParams > 0 )
   {
     vtkWriter.addCellData( elDat, "el. Parameters", nofElParams );
-    vtkWriter.addVertexData( vtxDat, "vtx. Parameters", nofVtxParams );
+    //vtkWriter.addVertexData( vtxDat, "vtx. Parameters", nofVtxParams );
   }
   vtkWriter.write( name );
 }

Bye
Christoph

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