From 5f2e401ef77e4fbcc29d668f9d3a9280cde81754 Mon Sep 17 00:00:00 2001
From: Martin Kronbichler <kronbichler@lnm.mw.tum.de>
Date: Sat, 10 Mar 2018 07:10:18 +0100
Subject: [PATCH] Do not use MPI_COMM_WORLD.

---
 include/deal.II/multigrid/mg_transfer.h | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/deal.II/multigrid/mg_transfer.h b/include/deal.II/multigrid/mg_transfer.h
index b13fb5fb2d..2608dedbf8 100644
--- a/include/deal.II/multigrid/mg_transfer.h
+++ b/include/deal.II/multigrid/mg_transfer.h
@@ -66,9 +66,16 @@ namespace internal
     template <typename SparsityPatternType, typename DoFHandlerType>
     static void reinit(Matrix &matrix, Sparsity &, int level, const SparsityPatternType &sp, DoFHandlerType &dh)
     {
+      const parallel::Triangulation<DoFHandlerType::dimension,DoFHandlerType::space_dimension> *dist_tria =
+        dynamic_cast<const parallel::Triangulation<DoFHandlerType::dimension,DoFHandlerType::space_dimension>*>
+        (&(dh.get_triangulation()));
+      MPI_Comm communicator = dist_tria != nullptr ?
+                              dist_tria->get_communicator() :
+                              MPI_COMM_SELF;
+
       matrix.reinit(dh.locally_owned_mg_dofs(level+1),
                     dh.locally_owned_mg_dofs(level),
-                    sp, MPI_COMM_WORLD, true);
+                    sp, communicator, true);
     }
 
   };
@@ -82,9 +89,15 @@ namespace internal
     template <typename SparsityPatternType, typename DoFHandlerType>
     static void reinit(Matrix &matrix, Sparsity &, int level, const SparsityPatternType &sp, DoFHandlerType &dh)
     {
+      const parallel::Triangulation<DoFHandlerType::dimension,DoFHandlerType::space_dimension> *dist_tria =
+        dynamic_cast<const parallel::Triangulation<DoFHandlerType::dimension,DoFHandlerType::space_dimension>*>
+        (&(dh.get_triangulation()));
+      MPI_Comm communicator = dist_tria != nullptr ?
+                              dist_tria->get_communicator() :
+                              MPI_COMM_SELF;
       matrix.reinit(dh.locally_owned_mg_dofs(level+1),
                     dh.locally_owned_mg_dofs(level),
-                    sp, MPI_COMM_WORLD, true);
+                    sp, communicator, true);
     }
 
   };
@@ -99,9 +112,15 @@ namespace internal
     template <typename SparsityPatternType, typename DoFHandlerType>
     static void reinit(Matrix &matrix, Sparsity &, int level, const SparsityPatternType &sp, DoFHandlerType &dh)
     {
+      const parallel::Triangulation<DoFHandlerType::dimension,DoFHandlerType::space_dimension> *dist_tria =
+        dynamic_cast<const parallel::Triangulation<DoFHandlerType::dimension,DoFHandlerType::space_dimension>*>
+        (&(dh.get_triangulation()));
+      MPI_Comm communicator = dist_tria != nullptr ?
+                              dist_tria->get_communicator() :
+                              MPI_COMM_SELF;
       matrix.reinit(dh.locally_owned_mg_dofs(level+1),
                     dh.locally_owned_mg_dofs(level),
-                    sp, MPI_COMM_WORLD, true);
+                    sp, communicator, true);
     }
   };
 #endif
-- 
2.39.5