Improved the maxQuality bound.

src/xmtrclusters/Problem.java

@@ -3,6 +3,7 @@ package xmtrclusters;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -65,21 +66,20 @@ public final class Problem {
       }
       assignedUsers.get(best[u]).add(u);
     }
-    // The maximum quality for each user occurs when the worst transmitter for
-    // that user is the only transmitter not in the user's cluster.
+    // The maximum quality for each user occurs when the C best transmitters
+    // for that user form a cluster, where C is the upper limit on cluster
+    // size.
     maxQuality = new double[nUsers];
     for (int u = 0; u < nUsers; u++) {
-      double worst = Double.MAX_VALUE;
-      int w = -1;
+      ArrayList<Double> w = new ArrayList<>();
       for (int t = 0; t < nTrans; t++) {
-        if (weight[t][u] < worst) {
-          worst = weight[t][u];
-          w = t;
-        }
+        w.add(weight[t][u]);
       }
-      HashSet<Integer> c = new HashSet<>(allTransmitters);
-      c.remove(w);
-      maxQuality[u] = userQuality(u, c);
+      maxQuality[u] =
+        w.stream().sorted(Comparator.reverseOrder()).limit(maxSize)
+         .mapToDouble(d -> d).sum()
+        / w.stream().sorted(Comparator.reverseOrder()).skip(maxSize)
+           .mapToDouble(d -> d).sum();
     }
   }