From: Matthias Maier <tamiko@43-1.org>
Date: Fri, 5 Jul 2024 23:02:20 +0000 (-0500)
Subject: distributed::Triangulation: broadcast proper p4est checksum over all ranks
X-Git-Tag: v9.6.0-rc1~125^2~5
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=893a8f8766c07a6967152b380b4867faa6ee9499;p=dealii.git

distributed::Triangulation: broadcast proper p4est checksum over all ranks
---

diff --git a/source/distributed/tria.cc b/source/distributed/tria.cc
index 6f87521425..9063b2253c 100644
--- a/source/distributed/tria.cc
+++ b/source/distributed/tria.cc
@@ -2274,7 +2274,22 @@ namespace parallel
       Assert(parallel_forest != nullptr,
              ExcMessage(
                "Can't produce a check sum when no forest is created yet."));
-      return dealii::internal::p4est::functions<dim>::checksum(parallel_forest);
+
+      auto checksum =
+        dealii::internal::p4est::functions<dim>::checksum(parallel_forest);
+
+#  if !DEAL_II_P4EST_VERSION_GTE(2, 8, 6, 0)
+      /*
+       * p4est prior to 2.8.6 returns the proper checksum only on rank 0
+       * and simply "0" on all other ranks. This is not really what we
+       * want, thus broadcast the correct value to all other ranks:
+       */
+      checksum = Utilities::MPI::broadcast(this->mpi_communicator,
+                                           checksum,
+                                           /*root_process*/ 0);
+#  endif
+
+      return checksum;
     }