Add method description for fractional marking.

dune/fufem/estimators/fractionalmarking.hh

@@ -15,6 +15,7 @@
 
 #include <dune/fufem/estimators/refinementindicator.hh>
 
+//! \brief See static method @mark for details.
 template <class GridType, class field_type = double>
 class FractionalMarkingStrategy
 {
@@ -40,6 +41,17 @@ public:
                      const std::vector<GridType*>& grids,
                      field_type fraction);
 
+    /**
+     * \brief Sorts the elements of all grids according to the maximal error
+     * associated with any of its subentities and marks the top percentage of
+     * those (for refinement).
+     * \param refinementIndicator For each grid, the errors associated with its
+     * entities are provided here.
+     * \param fraction Specifies the total number of elements to be refined in
+     * terms of percentage/100 of all elements of all grids.
+     */
+    // TODO: IMHO the implementation does not provide a mechanism that prevents
+    // refining elements where all associated errors are zero.
     static void mark(const std::vector<std::shared_ptr<RefinementIndicator<GridType> > >& refinementIndicator,
                      const std::vector<GridType*>& grids,
                      field_type fraction);