Added missing overloads to SparseGrid.

Solves a bug with METAD + TARGET + GRID_SPARSE
See also #467

src/tools/Grid.cpp

@@ -821,6 +821,24 @@ void SparseGrid::writeToFile(OFile& ofile) {
   }
 }
 
+double SparseGrid::getMinValue() const {
+  double minval;
+  minval=0.0;
+  for(auto const & i : map_) {
+    if(i.second<minval) minval=i.second;
+  }
+  return minval;
+}
+
+double SparseGrid::getMaxValue() const {
+  double maxval;
+  maxval=0.0;
+  for(auto const & i : map_) {
+    if(i.second>maxval) maxval=i.second;
+  }
+  return maxval;
+}
+
 
 void Grid::projectOnLowDimension(double &val, std::vector<int> &vHigh, WeightBase * ptr2obj ) {
   unsigned i=0;

src/tools/Grid.h

@@ -271,6 +271,10 @@ public:
   void writeToFile(OFile&);
 
   virtual ~SparseGrid() {}
+
+  virtual double getMaxValue() const;
+  virtual double getMinValue() const;
+
 };
 }