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// $Id: petsc_sparse_matrix.h 30040 2013-07-18 17:06:48Z maier $
//
// Copyright (C) 2004 - 2013 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the deal.II distribution.
//
// ---------------------------------------------------------------------
#ifndef __deal2__petsc_sparse_matrix_h
#define __deal2__petsc_sparse_matrix_h
#include <deal.II/base/config.h>
#ifdef DEAL_II_WITH_PETSC
# include <deal.II/lac/exceptions.h>
# include <deal.II/lac/petsc_matrix_base.h>
# include <vector>
DEAL_II_NAMESPACE_OPEN
// forward declaration
template <typename MatrixType> class BlockMatrixBase;
namespace PETScWrappers
{
/**
* Implementation of a sequential sparse matrix class based on PETSC. All the
* functionality is actually in the base class, except for the calls to
* generate a sequential sparse matrix. This is possible since PETSc only works
* on an abstract matrix type and internally distributes to functions that do
* the actual work depending on the actual matrix type (much like using
* virtual functions). Only the functions creating a matrix of specific type
* differ, and are implemented in this particular class.
*
* @ingroup PETScWrappers
* @ingroup Matrix1
* @author Wolfgang Bangerth, 2004
*/
class SparseMatrix : public MatrixBase
{
public:
/**
* A structure that describes some of
* the traits of this class in terms of
* its run-time behavior. Some other
* classes (such as the block matrix
* classes) that take one or other of
* the matrix classes as its template
* parameters can tune their behavior
* based on the variables in this
* class.
*/
struct Traits
{
/**
* It is safe to elide additions of
* zeros to individual elements of
* this matrix.
*/
static const bool zero_addition_can_be_elided = true;
};
/**
* Default constructor. Create an empty
* matrix.
*/
SparseMatrix ();
/**
* Create a sparse matrix of dimensions
* @p m times @p n, with an
* initial guess of
* @p n_nonzero_per_row nonzero
* elements per row. PETSc is able to
* cope with the situation that more
* than this number of elements is
* later allocated for a row, but this
* involves copying data, and is thus
* expensive.
*
* The @p is_symmetric flag determines
* whether we should tell PETSc that
* the matrix is going to be symmetric
* (as indicated by the call
* <tt>MatSetOption(mat,
* MAT_SYMMETRIC)</tt>. Note that the
* PETSc documentation states that one
* cannot form an ILU decomposition of
* a matrix for which this flag has
* been set to @p true, only an
* ICC. The default value of this flag
* is @p false.
*/
SparseMatrix (const size_type m,
const size_type n,
const size_type n_nonzero_per_row,
const bool is_symmetric = false);
/**
* Initialize a rectangular matrix with
* @p m rows and @p n
* columns. The maximal number of
* nonzero entries for each row
* separately is given by the
* @p row_lengths array.
*
* Just as for the other constructors:
* PETSc is able to cope with the
* situation that more than this number
* of elements is later allocated for a
* row, but this involves copying data,
* and is thus expensive.
*
* The @p is_symmetric flag determines
* whether we should tell PETSc that
* the matrix is going to be symmetric
* (as indicated by the call
* <tt>MatSetOption(mat,
* MAT_SYMMETRIC)</tt>. Note that the
* PETSc documentation states that one
* cannot form an ILU decomposition of
* a matrix for which this flag has
* been set to @p true, only an
* ICC. The default value of this flag
* is @p false.
*/
SparseMatrix (const size_type m,
const size_type n,
const std::vector<size_type> &row_lengths,
const bool is_symmetric = false);
/**
* Initialize a sparse matrix using the
* given sparsity pattern.
*
* Note that PETSc can be very slow
* if you do not provide it with a
* good estimate of the lengths of
* rows. Using the present function
* is a very efficient way to do
* this, as it uses the exact number
* of nonzero entries for each row of
* the matrix by using the given
* sparsity pattern argument. If the
* @p preset_nonzero_locations flag
* is @p true, this function in
* addition not only sets the correct
* row sizes up front, but also
* pre-allocated the correct nonzero
* entries in the matrix.
*
* PETsc allows to later add
* additional nonzero entries to a
* matrix, by simply writing to these
* elements. However, this will then
* lead to additional memory
* allocations which are very
* inefficient and will greatly slow
* down your program. It is therefore
* significantly more efficient to
* get memory allocation right from
* the start.
*/
template <typename SparsityType>
explicit SparseMatrix (const SparsityType &sparsity_pattern,
const bool preset_nonzero_locations = true);
/**
* This operator assigns a scalar to
* a matrix. Since this does usually
* not make much sense (should we set
* all matrix entries to this value?
* Only the nonzero entries of the
* sparsity pattern?), this operation
* is only allowed if the actual
* value to be assigned is zero. This
* operator only exists to allow for
* the obvious notation
* <tt>matrix=0</tt>, which sets all
* elements of the matrix to zero,
* but keep the sparsity pattern
* previously used.
*/
SparseMatrix &operator = (const double d);
/**
* Throw away the present matrix and
* generate one that has the same
* properties as if it were created by
* the constructor of this class with
* the same argument list as the
* present function.
*/
void reinit (const size_type m,
const size_type n,
const size_type n_nonzero_per_row,
const bool is_symmetric = false);
/**
* Throw away the present matrix and
* generate one that has the same
* properties as if it were created by
* the constructor of this class with
* the same argument list as the
* present function.
*/
void reinit (const size_type m,
const size_type n,
const std::vector<size_type> &row_lengths,
const bool is_symmetric = false);
/**
* Initialize a sparse matrix using the
* given sparsity pattern.
*
* Note that PETSc can be very slow
* if you do not provide it with a
* good estimate of the lengths of
* rows. Using the present function
* is a very efficient way to do
* this, as it uses the exact number
* of nonzero entries for each row of
* the matrix by using the given
* sparsity pattern argument. If the
* @p preset_nonzero_locations flag
* is @p true, this function in
* addition not only sets the correct
* row sizes up front, but also
* pre-allocated the correct nonzero
* entries in the matrix.
*
* PETsc allows to later add
* additional nonzero entries to a
* matrix, by simply writing to these
* elements. However, this will then
* lead to additional memory
* allocations which are very
* inefficient and will greatly slow
* down your program. It is therefore
* significantly more efficient to
* get memory allocation right from
* the start.
*
* Despite the fact that it would
* seem to be an obvious win, setting
* the @p preset_nonzero_locations
* flag to @p true doesn't seem to
* accelerate program. Rather on the
* contrary, it seems to be able to
* slow down entire programs
* somewhat. This is suprising, since
* we can use efficient function
* calls into PETSc that allow to
* create multiple entries at once;
* nevertheless, given the fact that
* it is inefficient, the respective
* flag has a default value equal to
* @p false.
*/
template <typename SparsityType>
void reinit (const SparsityType &sparsity_pattern,
const bool preset_nonzero_locations = true);
/**
* Return a reference to the MPI
* communicator object in use with this
* matrix. Since this is a sequential
* matrix, it returns the MPI_COMM_SELF
* communicator.
*/
virtual const MPI_Comm &get_mpi_communicator () const;
/**
* Return the square of the norm
* of the vector $v$ with respect
* to the norm induced by this
* matrix,
* i.e. $\left(v,Mv\right)$. This
* is useful, e.g. in the finite
* element context, where the
* $L_2$ norm of a function
* equals the matrix norm with
* respect to the mass matrix of
* the vector representing the
* nodal values of the finite
* element function.
*
* Obviously, the matrix needs to
* be quadratic for this operation.
*
* The implementation of this function
* is not as efficient as the one in
* the @p MatrixBase class used in
* deal.II (i.e. the original one, not
* the PETSc wrapper class) since PETSc
* doesn't support this operation and
* needs a temporary vector.
*/
PetscScalar matrix_norm_square (const VectorBase &v) const;
/**
* Compute the matrix scalar
* product $\left(u,Mv\right)$.
*
* The implementation of this function
* is not as efficient as the one in
* the @p MatrixBase class used in
* deal.II (i.e. the original one, not
* the PETSc wrapper class) since PETSc
* doesn't support this operation and
* needs a temporary vector.
*/
PetscScalar matrix_scalar_product (const VectorBase &u,
const VectorBase &v) const;
private:
/**
* Purposefully not implemented
*/
SparseMatrix(const SparseMatrix &);
/**
* Purposefully not implemented
*/
SparseMatrix &operator= (const SparseMatrix &);
/**
* Do the actual work for the
* respective reinit() function and the
* matching constructor, i.e. create a
* matrix. Getting rid of the previous
* matrix is left to the caller.
*/
void do_reinit (const size_type m,
const size_type n,
const size_type n_nonzero_per_row,
const bool is_symmetric = false);
/**
* Same as previous function.
*/
void do_reinit (const size_type m,
const size_type n,
const std::vector<size_type> &row_lengths,
const bool is_symmetric = false);
/**
* Same as previous function.
*/
template <typename SparsityType>
void do_reinit (const SparsityType &sparsity_pattern,
const bool preset_nonzero_locations);
/**
* To allow calling protected
* prepare_add() and
* prepare_set().
*/
friend class BlockMatrixBase<SparseMatrix>;
};
}
DEAL_II_NAMESPACE_CLOSE
#endif // DEAL_II_WITH_PETSC
/*---------------------------- petsc_sparse_matrix.h ---------------------------*/
#endif
/*---------------------------- petsc_sparse_matrix.h ---------------------------*/
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