From 1a2973c4f47332d2bf3369ef43ec0cef510e77ab Mon Sep 17 00:00:00 2001
From: mattijs <mattijs>
Date: Fri, 21 May 2010 16:54:55 +0100
Subject: [PATCH] ENH: added to splitCyclic.txt changes file.

---
 doc/changes/splitCyclic.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/doc/changes/splitCyclic.txt b/doc/changes/splitCyclic.txt
index fc0ff4880f..814dfe0850 100644
--- a/doc/changes/splitCyclic.txt
+++ b/doc/changes/splitCyclic.txt
@@ -104,6 +104,14 @@ type 'processorCyclic'.
 
 - processor patches use overlapping communication using a different message
 tag. This maps straight through into the MPI message tag.
+See processorCyclicPolyPatch::tag(). This needs to be calculated the
+same on both sides so is calculated as
+        Pstream::nProcs()*max(myProcNo, neighbProcNo)
+      + min(myProcNo, neighbProcNo)
+which is
+- unique
+- commutative
+- does not interfere with the default tag (= 1)
 
 
 - when constructing a GeometricField from a dictionary it will explicitly