Enable gmashreader for parallel programs

This makes it possible to use gmshreader for parallel programs similar to StructuredGridFactory by only filling the grid factory if rank==0.

dune/grid/io/file/gmshreader.hh

@@ -664,9 +664,12 @@ namespace Dune
// make a grid factory
Dune::GridFactory<Grid> factory;
-      // create parse object
-      GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
-      parser.read(fileName);
+      // only fill grid factory for rank 0
+      if (MPIHelper::getCollectiveCommunication().rank() == 0){
+        // create parse object
+        GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
+        parser.read(fileName);
+      }
return factory.createGrid();
}
@@ -680,12 +683,15 @@ namespace Dune
// make a grid factory
Dune::GridFactory<Grid> factory;
-      // create parse object
-      GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
-      parser.read(fileName);
-      boundarySegmentToPhysicalEntity.swap(parser.boundaryIdMap());
-      elementToPhysicalEntity.swap(parser.elementIndexMap());
+      // only fill grid factory for rank 0
+      if (MPIHelper::getCollectiveCommunication().rank() == 0){
+        // create parse object
+        GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
+        parser.read(fileName);
+        boundarySegmentToPhysicalEntity.swap(parser.boundaryIdMap());
+        elementToPhysicalEntity.swap(parser.elementIndexMap());
+      }
return factory.createGrid();
}
@@ -694,9 +700,12 @@ namespace Dune
static void read (Dune::GridFactory<Grid>& factory, const std::string& fileName,
bool verbose = true, bool insertBoundarySegments=true)
{
-      // create parse object
-      GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
-      parser.read(fileName);
+      // only fill grid factory for rank 0
+      if (MPIHelper::getCollectiveCommunication().rank() == 0){
+        // create parse object
+        GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
+        parser.read(fileName);
+      }
}
/** \todo doc me */
@@ -706,12 +715,15 @@ namespace Dune
std::vector<int>& elementToPhysicalEntity,
bool verbose = true, bool insertBoundarySegments=true)
{
-      // create parse object
-      GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
-      parser.read(fileName);
-
-      boundarySegmentToPhysicalEntity.swap(parser.boundaryIdMap());
-      elementToPhysicalEntity.swap(parser.elementIndexMap());
+      // only fill grid factory for rank 0
+      if (MPIHelper::getCollectiveCommunication().rank() == 0){
+        // create parse object
+        GmshReaderParser<Grid> parser(factory,verbose,insertBoundarySegments);
+        parser.read(fileName);
+
+        boundarySegmentToPhysicalEntity.swap(parser.boundaryIdMap());
+        elementToPhysicalEntity.swap(parser.elementIndexMap());
+      }
}
};