Run GridMapper algorithms for parallel runs only

dune/dorie/solver/util_grid_mapper.hh

@@ -61,20 +61,23 @@ public:
         _element_index_map(element_index_map),
         _boundary_index_map(boundary_index_map)
     {
-        // create a mapping using global persistent IDs
-        auto id_map = build_id_map();
-        // broadcast this map
-        broadcast_id_map(id_map);
-
-        // load-balance the grid to all processors
-        _grid->loadBalance();
-        _mapper.update();
-
-        // rebuild the index map for local grid partition
-        rebuild_index_maps(id_map);
-
-        // broadcast the (global) boundary map
-        broadcast_vector(_boundary_index_map);
+        if (_gv.comm().size() > 1)
+        {
+            // create a mapping using global persistent IDs
+            auto id_map = build_id_map();
+            // broadcast this map
+            broadcast_id_map(id_map);
+
+            // load-balance the grid to all processors
+            _grid->loadBalance();
+            _mapper.update();
+
+            // rebuild the index map for local grid partition
+            rebuild_index_maps(id_map);
+
+            // broadcast the (global) boundary map
+            broadcast_vector(_boundary_index_map);
+        }
     }
 
     /// Create a GridMapper for a rectangular grid using cell coordinates.
@@ -101,16 +104,19 @@ public:
         _element_index_map(element_index_map),
         _boundary_index_map(boundary_index_map)
     {
-        // load-balance the grid to all processors
-        // (might have happened already)
-        _grid->loadBalance();
-        _mapper.update();
-
-        // broadcast the index vectors
-        broadcast_vector(element_index_map);
-
-        // recompute stuff
-        rebuild_index_maps(cells);
+        if (_gv.comm().size() > 1)
+        {
+            // load-balance the grid to all processors
+            // (might have happened already)
+            _grid->loadBalance();
+            _mapper.update();
+
+            // broadcast the index vectors
+            broadcast_vector(element_index_map);
+
+            // recompute stuff
+            rebuild_index_maps(cells);
+        }
     }
 
     /// Return a reference to the element index map