message: Fix nvcc sign warning
diff: @@ -1861,7 +1861,7 @@ struct WeightMinHeap
  void push(size_t i)
  {
  double val = w[i];
  - c.push_back(-1);
  + c.push_back(0);
  size_t pos = c.size()-1;
  pos = percolate_up(pos, val);
  c[pos] = i;
  