Feature/simd for multi rhs

Update the solvers to solve for multiple rhs vectors simultaniously. This makes use of SIMD abstractions in dune-common (see dune-common!16 (merged)) to use vectors of SIMD vectors as FieldType of the right-hand-side. By this we can make immediate use of SIMD units in modern processors. Using SSE for example we get a speedup of 2 basically for free. This extension is useful whenever the same operator has to be solved for many rhs vectors, e.g. in the case of MS-FEM.

AMG Ist working as long as the coarse grid solver is an iterative solver. I therefore added an additional preprocessor macro to disable the direct coarse solver explicitly.

What is missing currently is multi-rhs support for the direct solvers. I'm preparing a separate merge request for this feature, which will add multi-rhs direct-coarse-grid support for the AMG.

See also: dune-common!81 (merged), dune-geometry!13 (closed).

dune/istl/eigenvalue/poweriteration.hh

@@ -124,55 +124,6 @@ namespace Dune
     };
   } // end namespace Impl
 
-  /**
-   * \brief Helper class for notifying a DUNE-ISTL linear solver about
-   *        a change of the iteration matrix object in a unified way,
-   *        i.e. independent from the solver's type (direct/iterative).
-   *
-   * \author Sebastian Westerheide.
-   */
-  template <typename ISTLLinearSolver, typename BCRSMatrix>
-  class SolverHelper
-  {
-  public:
-    static void setMatrix (ISTLLinearSolver& solver,
-                           const BCRSMatrix& matrix)
-    {
-      static const bool is_direct_solver
-        = Dune::IsDirectSolver<ISTLLinearSolver>::value;
-      SolverHelper<ISTLLinearSolver,BCRSMatrix>::
-        Implementation<is_direct_solver>::setMatrix(solver,matrix);
-    }
-
-  protected:
-    /**
-     * \brief Implementation that works together with iterative ISTL
-     *        solvers, e.g. Dune::CGSolver or Dune::BiCGSTABSolver.
-     */
-    template <bool is_direct_solver, typename Dummy = void>
-    struct Implementation
-    {
-      static void setMatrix (ISTLLinearSolver&,
-                             const BCRSMatrix&)
-      {}
-    };
-
-    /**
-     * \brief Implementation that works together with direct ISTL
-     *        solvers, e.g. Dune::SuperLU or Dune::UMFPack.
-     */
-    template <typename Dummy>
-    struct Implementation<true,Dummy>
-    {
-      static void setMatrix (ISTLLinearSolver& solver,
-                             const BCRSMatrix& matrix)
-      {
-        solver.setMatrix(matrix);
-      }
-    };
-  };
-
-
   /**
    * \brief Iterative eigenvalue algorithms based on power iteration.
    *