[dune-functions] Problems writing vector-valued vtk files

[Oliver Sander]

Hi guys,
I am trying to get the new vtkwriter to write vector-valued functions,
and I can't get it to work.  Is this a bug or am I forgetting some important
option?  To reproduce, please apply the attached short patch to poisson-pq2.cc.
Then, running the program aborts with

poisson-pq2: /home/sander/dune/dune-common/dune/common/densevector.hh:538: typename Dune::PromotionTraits<typename Dune::DenseMatVecTraits<V>::value_type, typename
Dune::DenseVector<Other>::field_type>::PromotedType Dune::DenseVector<V>::operator*(const Dune::DenseVector<Other>&) const [with Other = Dune::FieldVector<double, 1>; V = Dune::FieldVector<double, 3>;
typename Dune::PromotionTraits<typename Dune::DenseMatVecTraits<V>::value_type, typename Dune::DenseVector<Other>::field_type>::PromotedType = double]: Assertion `y.size() == size()' failed.
Abgebrochen

Thanks for your help,
Oliver



diff --git a/examples/poisson-pq2.cc b/examples/poisson-pq2.cc
index 944aacc..6b5a079 100644
--- a/examples/poisson-pq2.cc
+++ b/examples/poisson-pq2.cc
@@ -20,7 +20,7 @@
 #include <dune/istl/solvers.hh>

 #include <dune/functions/functionspacebases/interpolate.hh>
-#include <dune/functions/functionspacebases/pq2nodalbasis.hh>
+#include <dune/functions/functionspacebases/pq1nodalbasis.hh>
 #include <dune/functions/gridfunctions/discretescalarglobalbasisfunction.hh>
 #include <dune/functions/gridfunctions/gridviewfunction.hh>

@@ -304,7 +304,7 @@ int main (int argc, char *argv[]) try
   //   Choose a finite element space
   /////////////////////////////////////////////////////////

-  typedef Functions::PQ2NodalBasis<GridView> FEBasis;
+  typedef Functions::PQ1NodalBasis<GridView> FEBasis;
   FEBasis feBasis(gridView);

   /////////////////////////////////////////////////////////
@@ -399,6 +399,7 @@ int main (int argc, char *argv[]) try
   //  Make a discrete function from the FE basis and the coefficient vector
   ////////////////////////////////////////////////////////////////////////////

+#if 0
   Dune::Functions::DiscreteScalarGlobalBasisFunction<decltype(feBasis),decltype(x)> xFunction(feBasis,x);
   auto localXFunction = localFunction(xFunction);

@@ -410,6 +411,23 @@ int main (int argc, char *argv[]) try
   SubsamplingVTKWriter<GridView> vtkWriter(gridView,2);
   vtkWriter.addVertexData(localXFunction, VTK::FieldInfo("x", VTK::FieldInfo::Type::scalar, 1));
   vtkWriter.write("poisson-pq2");
+#else
+  typedef BlockVector<FieldVector<double,3> > EmbeddedVectorType;
+  EmbeddedVectorType xEmbedded(x.size());
+  for (size_t i=0; i<x.size(); i++) {
+    xEmbedded[i][0] = 0;
+    xEmbedded[i][1] = 0;
+    xEmbedded[i][2] = 0;
+  }
+
+  Dune::Functions::DiscreteScalarGlobalBasisFunction<decltype(feBasis),decltype(xEmbedded)> xFunction(feBasis,xEmbedded);
+  auto localXFunction = localFunction(xFunction);
+
+  VTKWriter<GridView> vtkWriter(gridView);
+  vtkWriter.addVertexData(localXFunction, VTK::FieldInfo("x", VTK::FieldInfo::Type::scalar, 3));
+
+  vtkWriter.write("test");
+#endif

  }
 // Error handling
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