Add Dune::Solvers::Preconditioner

[[Imported from SVN: r11958]]

dune/solvers/common/preconditioner.hh

@@ -21,4 +21,22 @@ public:
     
 };
 
+namespace Dune {
+    namespace Solvers {
+
+        /** \brief Abstract base class for preconditioners
+         */
+        template <class MatrixType, class VectorType, class BitVectorType
+                  = Dune::BitSetVector<VectorType::block_type::dimension> >
+        class Preconditioner : public NumProc
+        {
+        public:
+            virtual ~Preconditioner() {}
+
+            virtual void check() const {}
+            virtual void setMatrix(const MatrixType& matrix) = 0;
+            virtual void apply(VectorType& x, const VectorType& r) = 0;
+        };
+    }
+}
 #endif