From 7064b96260ca635950600adeffff20b40df04404 Mon Sep 17 00:00:00 2001
From: Markus Blatt <markus@dr-blatt.de>
Date: Wed, 21 Nov 2018 10:28:40 +0100
Subject: [PATCH] Test for next neighbour without using abs.

Substraction of two unsigned int might cause trouble as
the result might have to be signed to be meaningful. In
addition there have overload resolution issues with g++-7.
---
 .../eclipse/EclipseState/Edit/EDITNNC.cpp     | 20 +++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/opm/parser/eclipse/EclipseState/Edit/EDITNNC.cpp b/src/opm/parser/eclipse/EclipseState/Edit/EDITNNC.cpp
index 7f7a47515..b1e21758f 100644
--- a/src/opm/parser/eclipse/EclipseState/Edit/EDITNNC.cpp
+++ b/src/opm/parser/eclipse/EclipseState/Edit/EDITNNC.cpp
@@ -15,6 +15,23 @@
 namespace Opm
 {
 
+bool isNeighbor(const std::array<size_t, 3>& ijk1, const std::array<size_t, 3>& ijk2)
+{
+    if ( (ijk1[0] + 1) == ijk2[0] || (ijk1[0] - 1) == ijk2[0] )
+    {
+        return ijk1[1] == ijk2[1] && ijk1[2] == ijk2[2];
+    }
+    if  ( (ijk1[1] + 1) == ijk2[1] || (ijk1[1] - 1) == ijk2[1] )
+    {
+        return ijk1[0] == ijk2[0] && ijk1[2] == ijk2[2];
+    }
+    if( (ijk1[2] + 1) == ijk2[2] || (ijk1[2] - 1) == ijk2[2] )
+    {
+        return ijk1[1] == ijk2[1] && ijk1[1] == ijk2[1];
+    }
+    return false;
+}
+
 void readEditNncs(const std::vector< const DeckKeyword* >& editNncsKw, std::vector<NNCdata>& editNncs, const GridDims& gridDims)
 {
     for (size_t idx_nnc = 0; idx_nnc<editNncsKw.size(); ++idx_nnc) {
@@ -35,8 +52,7 @@ void readEditNncs(const std::vector< const DeckKeyword* >& editNncsKw, std::vect
                 
             const double trans = nnc.getRecord(i).getItem(6).get<double>(0);
             using std::abs;
-            if ( ( abs(ijk1[0]-ijk2[0]) > 1 ) || ( abs(ijk1[1]-ijk2[1]) > 1 ) ||
-                 ( abs(ijk1[2]-ijk2[2]) > 1 ) )
+            if ( !isNeighbor(ijk1, ijk2) )
             {
                 editNncs.emplace_back(global_index1, global_index2, trans);
             }