From: Martin Kronbichler <martin.kronbichler@uni-a.de>
Date: Mon, 20 Jun 2022 15:06:10 +0000 (+0200)
Subject: Query ghost index set only once in Partitioner::global_to_local
X-Git-Tag: v9.5.0-rc1~1179^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f07228e9f1ca4bb654c4d0fa6d9066b7b9ccb1d9;p=dealii.git

Query ghost index set only once in Partitioner::global_to_local
---

diff --git a/include/deal.II/base/partitioner.h b/include/deal.II/base/partitioner.h
index 5596a99153..8664d39236 100644
--- a/include/deal.II/base/partitioner.h
+++ b/include/deal.II/base/partitioner.h
@@ -873,15 +873,19 @@ namespace Utilities
              ExcIndexNotPresent(global_index, my_pid));
       if (in_local_range(global_index))
         return static_cast<unsigned int>(global_index - local_range_data.first);
-      else if (is_ghost_entry(global_index))
-        return (locally_owned_size() +
-                static_cast<unsigned int>(
-                  ghost_indices_data.index_within_set(global_index)));
       else
-        // should only end up here in optimized mode, when we use this large
-        // number to trigger a segfault when using this method for array
-        // access
-        return numbers::invalid_unsigned_int;
+        {
+          // avoid checking the ghost index set via a binary search twice by
+          // querying the index within set, which returns invalid_dof_index
+          // for non-existent entries
+          const types::global_dof_index index_within_ghosts =
+            ghost_indices_data.index_within_set(global_index);
+          if (index_within_ghosts == numbers::invalid_dof_index)
+            return numbers::invalid_unsigned_int;
+          else
+            return locally_owned_size() +
+                   static_cast<unsigned int>(index_within_ghosts);
+        }
     }