From: Denis Davydov <davydden@gmail.com>
Date: Tue, 21 Aug 2018 16:28:34 +0000 (+0200)
Subject: add a note why we have zeros in first_index
X-Git-Tag: v9.1.0-rc1~794^2~1
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cc15f3c5efe7c624ccb169ef8a3adfbac4dbcf4a;p=dealii.git

add a note why we have zeros in first_index
---

diff --git a/source/base/partitioner.cc b/source/base/partitioner.cc
index 8a12409ddd..84d3b73f19 100644
--- a/source/base/partitioner.cc
+++ b/source/base/partitioner.cc
@@ -212,7 +212,9 @@ namespace Utilities
       first_index[n_procs] = global_size;
 
       // fix case when there are some processors without any locally owned
-      // indices: then there might be a zero in some entries
+      // indices: then there might be a zero in some entries. The reason
+      // is that local_range_data will contain [0,0) and second indix is
+      // incorrect inside the Allgather'ed first_index.
       if (global_size > 0)
         {
           unsigned int first_proc_with_nonzero_dofs = 0;