reduce float warnings (comparisons and implicit conversions)
diff --git a/test/sparse_basic.cpp b/test/sparse_basic.cpp
index 85a6077..8694490 100644
--- a/test/sparse_basic.cpp
+++ b/test/sparse_basic.cpp
@@ -679,7 +679,7 @@
   typedef typename SparseMatrixType::Scalar Scalar;
   typedef Triplet<Scalar,Index> TripletType;
   std::vector<TripletType> triplets;
-  double nelements = density * rows*cols;
+  double nelements = density * static_cast<double>(rows*cols);
   VERIFY(nelements>=0 && nelements < static_cast<double>(NumTraits<StorageIndex>::highest()));
   Index ntriplets = Index(nelements);
   triplets.reserve(ntriplets);