Debug rank computing when there is no dependency

core/instance.cpp

@@ -319,9 +319,12 @@ vector<double> Instance::computeRanks(vector<double> wbar, int to, int from) {
         int i = topOrder[j];
         // Compute max
         double m = -std::numeric_limits<double>::infinity();
-        for(int k = 0; k < (int) revDep[i].size(); k++)
+	if(revDep[i].empty())
+	  m = 0;
+	else 
+	  for(int k = 0; k < (int) revDep[i].size(); k++)
             if(rank[revDep[i][k]] > m)
-                m = rank[revDep[i][k]];
+	      m = rank[revDep[i][k]];
         rank[i] = wbar[i] + m;
 
         if (topOrder[j] == from)