BlockDiagonalMatrix

git-svn-id: https://svn.dealii.org/trunk@3524 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/lac/include/lac/block_matrix.h b/deal.II/lac/include/lac/block_matrix.h
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+//-------------------------------------------------------------------
+//    $Id$
+//    Version: $Name$
+//
+//    Copyright (C) 1998, 1999, 2000 by the deal.II authors
+//
+//    This file is subject to QPL and may not be  distributed
+//    without copyright and license information. Please refer
+//    to the file deal.II/doc/license.html for the  text  and
+//    further information on this license.
+//
+//-------------------------------------------------------------------
+#ifndef __deal2__block_matrix_h
+#define __deal2__block_matrix_h
+
+
+#include <base/exceptions.h>
+#include <base/smartpointer.h>
+#include <lac/block_vector.h>
+
+/**
+ * A matrix with several copies of the same block on the diagonal.
+ *
+ * This matrix implements an @p{m} by @p{m} block matrix. Each
+ * diagonal block consists of the same (non-block) matrix, while
+ * off-diagonal blocks are void.
+ *
+ * One special application is a one by one block matrix, allowing to
+ * apply the @p{vmult} of the original matrix (or preconditioner) to a
+ * block vector.
+ *
+ * @author Guido Kanschat, 2000
+ */
+template <class MATRIX>
+class BlockDiagonalMatrix : public Subscriptor
+{
+public:
+                                  /**
+                                   * Constructor for an @p{n_blocks}
+                                   * by @p{n_blocks} matrix with
+                                   * diagonal blocks @p{M}.
+                                   */
+  BlockDiagonalMatrix (const MATRIX& M,
+                      unsigned int n_blocks);
+
+                                  /**
+                                   * Matrix-vector-multiplication.
+                                   */
+  template <typename number1, typename number2>
+  void vmult (BlockVector<number1>& dst,
+             const BlockVector<number2>& src) const;
+  
+                                  /**
+                                   * Transposed matrix-vector-multiplication.
+                                   */
+  template <typename number1, typename number2>
+  void Tvmult (BlockVector<number1>& dst,
+              const BlockVector<number2>& src) const;
+private:
+                                  /**
+                                   * Number of blocks.
+                                   */
+  unsigned int num_blocks;
+                                  /**
+                                   * Diagonal entry.
+                                   */
+  SmartPointer<const MATRIX> matrix;
+};
+
+
+//----------------------------------------------------------------------//
+
+template <class MATRIX>
+BlockDiagonalMatrix<MATRIX>::BlockDiagonalMatrix (const MATRIX& M,
+                                                 unsigned int num_blocks)
+  : num_blocks (num_blocks),
+    matrix(&M)
+{}
+
+
+template <class MATRIX>
+template <typename number1, typename number2>
+void
+BlockDiagonalMatrix<MATRIX>::vmult (BlockVector<number1>& dst,
+                                    const BlockVector<number2>& src) const
+{
+  Assert (dst.n_blocks()==num_blocks,
+         ExcDimensionMismatch(dst.n_blocks(),num_blocks));
+  Assert (src.n_blocks()==num_blocks,
+         ExcDimensionMismatch(src.n_blocks(),num_blocks));
+
+  for (unsigned int i=0;i<num_blocks;++i)
+    matrix->vmult (dst.block(i), src.block(i));
+}
+
+
+template <class MATRIX>
+template <typename number1, typename number2>
+void
+BlockDiagonalMatrix<MATRIX>::Tvmult (BlockVector<number1>& dst,
+                                    const BlockVector<number2>& src) const
+{
+  Assert (dst.n_blocks()==num_blocks,
+         ExcDimensionMismatch(dst.n_blocks(),num_blocks));
+  Assert (src.n_blocks()==num_blocks,
+         ExcDimensionMismatch(src.n_blocks(),num_blocks));
+
+  for (unsigned int i=0;i<num_blocks;++i)
+    matrix->Tvmult (dst.block(i), src.block(i));
+}
+
+
+#endif
+