Fix zero-cost edges in TSP example

Author: Mikael Zayenz Lagerkvist

changelog.in

@@ -116,6 +116,16 @@ Thanks: Yuri Victorovich
 Do not create empty MiniZinc directories when FlatZinc is disabled in an
 Autotools build.
 
+[ENTRY]
+Module: example
+What: bug
+Rank: minor
+Issue: 151
+Thanks: Ioannis Papatsoris
+[DESCRIPTION]
+Treat zero entries in the TSP example as valid zero-cost edges. This lets the
+br17 instance reach its optimum.
+
 [ENTRY]
 Module: flatzinc
 What:   new

examples/tsp.cpp

@@ -244,12 +244,6 @@ class TSP : public IntMinimizeScript {
     // Cost matrix
     IntArgs c(n*n, p.d());
 
-    // Disallow disconnected nodes
-    for (int i=0; i<n; i++)
-      for (int j=0; j<n; j++)
-        if (p.d(i,j) == 0)
-          rel(*this, succ[i], IRT_NQ, j);
-
     // Cost of each edge
     IntVarArgs costs(*this, n, Int::Limits::min, Int::Limits::max);