Added hot start to first MIP model using heuristic solution. Second MIP model always rejects it.

src/xmtrclusters/XmtrClusters.java

@@ -5,6 +5,7 @@ import java.util.Collection;
 import solvers.GreedyConstruction;
 import solvers.MIPModel;
 import solvers.MIPModel2;
+import solvers.PairSwap;
 
 /**
  * XmtrClusters experiments with solutions to a problem of clustering
@@ -41,14 +42,23 @@ public final class XmtrClusters {
     if (g.isEmpty()) {
       System.out.println("\nThe greedy heuristic failed.");
     } else {
-      System.out.println("\nGreedy heuristic results:\n" + prob.report(g));
+      System.out.println("Greedy heuristic results:\n" + prob.report(g));
     }
     System.out.println("");
 
+    // Try the swapping heuristic.
+    long tl = 10000;  // run time limit (ms.)
+    PairSwap swap = new PairSwap(prob, g, tl);
+    Collection<Collection<Integer>> s = swap.getSolution();
+    System.out.println("Pairwise swapping results:\n" + prob.report(s));
+    System.out.println("");
+
     // Create and solve a MIP model.
     double timeLimit = 300;  // time limit in seconds for CPLEX
     try {
       MIPModel mip = new MIPModel(prob);
+      // Add the heuristic solution as a starting solution.
+      mip.hotStart(s);
       double obj = mip.solve(timeLimit);
       System.out.println("\nFinal objective value = " + obj);
       // Get and summarize the optimal transmitter clusters.