change output format for vtk files to allow parallel writes

src/amdis/FileWriter.hpp

@@ -86,9 +86,12 @@ namespace AMDiS
         vtkWriter_ = std::make_shared<Dune::VTKWriter<GridView>>(gridView());
 
       if (animation_)
-        vtkSeqWriter_ = std::make_shared<Dune::VTKSequenceWriter<GridView>>(vtkWriter_, filename_, dir_, "");
+        vtkSeqWriter_ = std::make_shared<Dune::VTKSequenceWriter<GridView>>(vtkWriter_, filename_, dir_, "data");
 
       vtkWriter_->addVertexData(discreteFct_, Dune::VTK::FieldInfo(name_, VTKFieldType<Range>, VTKFieldSize<Range>));
+
+      test_exit(dir_ == "." || filesystem::exists(dir_), "Output directory '{}' does not exist!",dir_);
+      filesystem::create_directories(dir_ + "/data");
     }
 
     void init(std::string const&, tag::unknown) {}
@@ -96,12 +99,10 @@ namespace AMDiS
     /// Implements \ref FileWriterInterface::writeFiles
     void writeFiles(AdaptInfo& adaptInfo, bool force) override
     {
-      test_exit(dir_ == "." || filesystem::exists(dir_), "Output directory '{}' does not exist!",dir_);
-
       if (vtkSeqWriter_)
         vtkSeqWriter_->write(adaptInfo.time(), mode_);
       else if (vtkWriter_)
-        vtkWriter_->write(filesystem::path({dir_, filename_}).string(), mode_);
+        vtkWriter_->pwrite(filename_, dir_, "data", mode_);
     }
 
   protected: