From: Timo Heister <timo.heister@gmail.com>
Date: Wed, 1 Jun 2022 16:05:00 +0000 (-0400)
Subject: add comment
X-Git-Tag: v9.4.0-rc1~94^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F13880%2Fhead;p=dealii.git

add comment
---

diff --git a/source/base/data_out_base.cc b/source/base/data_out_base.cc
index a7bbb7d98c..b7ea069b18 100644
--- a/source/base/data_out_base.cc
+++ b/source/base/data_out_base.cc
@@ -7786,9 +7786,11 @@ DataOutInterface<dim, spacedim>::write_vtu_in_parallel(
       }
   }
 
-  // Make sure we sync to disk. This ensures that the change in file
-  // size caused by the write_at() for the footer is visible for all
-  // ranks. Otherwise, the footer is sometimes lost.
+  // Make sure we sync to disk. As written in the standard,
+  // MPI_File_close() actually already implies a sync but there seems
+  // to be a bug on at least one configuration (running with multiple
+  // nodes using OpenMPI 4.1) that requires it. Without this call, the
+  // footer is sometimes missing.
   ierr = MPI_File_sync(fh);
   AssertThrowMPI(ierr);