From e2176b198ee7aed8f9fe08bd5b14ccf73ece40b4 Mon Sep 17 00:00:00 2001
From: Peter Munch <peterrmuench@gmail.com>
Date: Tue, 1 Jun 2021 22:34:57 +0200
Subject: [PATCH] Simplify workflow of repartitioning

Conflicts:
	source/grid/tria_description.cc
---
 .../mg_transfer_global_coarsening.templates.h | 40 +++++--------------
 .../repartitioning_policy_tools.cc            |  4 --
 source/grid/tria_description.cc               |  6 +++
 3 files changed, 15 insertions(+), 35 deletions(-)

diff --git a/include/deal.II/multigrid/mg_transfer_global_coarsening.templates.h b/include/deal.II/multigrid/mg_transfer_global_coarsening.templates.h
index a035af2fba..58ef8e9192 100644
--- a/include/deal.II/multigrid/mg_transfer_global_coarsening.templates.h
+++ b/include/deal.II/multigrid/mg_transfer_global_coarsening.templates.h
@@ -2357,26 +2357,13 @@ namespace MGTransferGlobalCoarseningTools
     else
       {
         // create triangulation description
-        TriangulationDescription::Description<dim, spacedim> construction_data;
-
-        if (repartition_fine_triangulation == true)
-          {
-            const auto partition = policy.partition(*fine_triangulation);
-
-            construction_data =
-              (partition.size() == 0) ?
-                TriangulationDescription::Utilities::
-                  create_description_from_triangulation(*fine_triangulation,
-                                                        comm) :
-                construction_data = TriangulationDescription::Utilities::
-                  create_description_from_triangulation(*fine_triangulation,
-                                                        partition);
-          }
-        else
-          {
-            construction_data = TriangulationDescription::Utilities::
+        const auto construction_data =
+          repartition_fine_triangulation ?
+            TriangulationDescription::Utilities::
+              create_description_from_triangulation(
+                *fine_triangulation, policy.partition(*fine_triangulation)) :
+            TriangulationDescription::Utilities::
               create_description_from_triangulation(*fine_triangulation, comm);
-          }
 
         // create new triangulation
         const auto new_fine_triangulation = std::make_shared<
@@ -2411,19 +2398,10 @@ namespace MGTransferGlobalCoarseningTools
         // coarsen mesh
         temp_triangulation_ptr->coarsen_global();
 
-        // perform partition
-        const auto partition = policy.partition(*temp_triangulation_ptr);
-        partition.update_ghost_values();
-
         // create triangulation description
-        const auto construction_data =
-          partition.size() == 0 ?
-            TriangulationDescription::Utilities::
-              create_description_from_triangulation(*temp_triangulation_ptr,
-                                                    comm) :
-            TriangulationDescription::Utilities::
-              create_description_from_triangulation(*temp_triangulation_ptr,
-                                                    partition);
+        const auto construction_data = TriangulationDescription::Utilities::
+          create_description_from_triangulation(
+            *temp_triangulation_ptr, policy.partition(*temp_triangulation_ptr));
 
         // create new triangulation
         const auto level_triangulation = std::make_shared<
diff --git a/source/distributed/repartitioning_policy_tools.cc b/source/distributed/repartitioning_policy_tools.cc
index 264bfb6b26..d13b788d90 100644
--- a/source/distributed/repartitioning_policy_tools.cc
+++ b/source/distributed/repartitioning_policy_tools.cc
@@ -152,8 +152,6 @@ namespace RepartitioningPolicyTools
           owning_ranks_of_coarse_cells[is_coarse.index_within_set(
             cell_id_translator.translate(cell))];
 
-    partition.update_ghost_values();
-
     return partition;
   }
 
@@ -219,8 +217,6 @@ namespace RepartitioningPolicyTools
     for (const auto i : partition.locally_owned_elements())
       partition[i] = convert(i);
 
-    partition.update_ghost_values();
-
     return partition;
   }
 
diff --git a/source/grid/tria_description.cc b/source/grid/tria_description.cc
index 6a86c6ecfb..31dd65a40b 100644
--- a/source/grid/tria_description.cc
+++ b/source/grid/tria_description.cc
@@ -750,6 +750,12 @@ namespace TriangulationDescription
         AssertDimension(partition.local_size(), 0);
 #endif
 
+      if (partition.size() == 0)
+        return create_description_from_triangulation(tria,
+                                                     tria.get_communicator());
+
+      partition.update_ghost_values();
+
       // 1) determine processes owning locally owned cells
       const std::vector<unsigned int> relevant_processes = [&]() {
         std::set<unsigned int> relevant_processes;
-- 
2.39.5