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//
// Copyright (C) 1999 - 2015 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 dealii__solver_richardson_h
#define dealii__solver_richardson_h
#include <deal.II/base/config.h>
#include <deal.II/base/logstream.h>
#include <deal.II/lac/solver.h>
#include <deal.II/lac/solver_control.h>
#include <deal.II/base/subscriptor.h>
DEAL_II_NAMESPACE_OPEN
/*!@addtogroup Solvers */
/*@{*/
/**
* Implementation of the preconditioned Richardson iteration method. The
* stopping criterion is the norm of the residual.
*
* For the requirements on matrices and vectors in order to work with this
* class, see the documentation of the Solver base class.
*
* Like all other solver classes, this class has a local structure called @p
* AdditionalData which is used to pass additional parameters to the solver,
* like damping parameters or the number of temporary vectors. We use this
* additional structure instead of passing these values directly to the
* constructor because this makes the use of the @p SolverSelector and other
* classes much easier and guarantees that these will continue to work even if
* number or type of the additional parameters for a certain solver changes.
*
* For the Richardson method, the additional data is the damping parameter,
* which is the only content of the @p AdditionalData structure. By default,
* the constructor of the structure sets it to one.
*
*
* <h3>Observing the progress of linear solver iterations</h3>
*
* The solve() function of this class uses the mechanism described in the
* Solver base class to determine convergence. This mechanism can also be used
* to observe the progress of the iteration.
*
*
* @author Ralf Hartmann
*/
template <class VectorType = Vector<double> >
class SolverRichardson : public Solver<VectorType>
{
public:
/**
* Standardized data struct to pipe additional data to the solver.
*/
struct AdditionalData
{
/**
* Constructor. By default, set the damping parameter to one.
*/
explicit
AdditionalData (const double omega = 1,
const bool use_preconditioned_residual = false);
/**
* Relaxation parameter.
*/
double omega;
/**
* Parameter for stopping criterion.
*/
bool use_preconditioned_residual;
};
/**
* Constructor.
*/
SolverRichardson (SolverControl &cn,
VectorMemory<VectorType> &mem,
const AdditionalData &data=AdditionalData());
/**
* Constructor. Use an object of type GrowingVectorMemory as a default to
* allocate memory.
*/
SolverRichardson (SolverControl &cn,
const AdditionalData &data=AdditionalData());
/**
* Virtual destructor.
*/
virtual ~SolverRichardson ();
/**
* Solve the linear system $Ax=b$ for x.
*/
template<typename MatrixType, typename PreconditionerType>
void
solve (const MatrixType &A,
VectorType &x,
const VectorType &b,
const PreconditionerType &precondition);
/**
* Solve $A^Tx=b$ for $x$.
*/
template<typename MatrixType, typename PreconditionerType>
void
Tsolve (const MatrixType &A,
VectorType &x,
const VectorType &b,
const PreconditionerType &precondition);
/**
* Set the damping-coefficient. Default is 1., i.e. no damping.
*/
void set_omega (const double om=1.);
/**
* Interface for derived class. This function gets the current iteration
* vector, the residual and the update vector in each step. It can be used
* for a graphical output of the convergence history.
*/
virtual void print_vectors (const unsigned int step,
const VectorType &x,
const VectorType &r,
const VectorType &d) const;
protected:
/**
* Implementation of the computation of the norm of the residual.
*/
virtual typename VectorType::value_type criterion();
/**
* Residual. Temporary vector allocated through the VectorMemory object at
* the start of the actual solution process and deallocated at the end.
*/
VectorType *Vr;
/**
* Preconditioned residual. Temporary vector allocated through the
* VectorMemory object at the start of the actual solution process and
* deallocated at the end.
*/
VectorType *Vd;
/**
* Control parameters.
*/
AdditionalData additional_data;
/**
* Within the iteration loop, the norm of the residual is stored in this
* variable. The function @p criterion uses this variable to compute the
* convergence value, which in this class is the norm of the residual vector
* and thus the square root of the @p res2 value.
*/
typename VectorType::value_type res;
};
/*@}*/
/*----------------- Implementation of the Richardson Method ------------------*/
#ifndef DOXYGEN
template <class VectorType>
inline
SolverRichardson<VectorType>::AdditionalData::
AdditionalData (const double omega,
const bool use_preconditioned_residual)
:
omega(omega),
use_preconditioned_residual(use_preconditioned_residual)
{}
template <class VectorType>
SolverRichardson<VectorType>::SolverRichardson(SolverControl &cn,
VectorMemory<VectorType> &mem,
const AdditionalData &data)
:
Solver<VectorType> (cn,mem),
additional_data(data)
{}
template <class VectorType>
SolverRichardson<VectorType>::SolverRichardson(SolverControl &cn,
const AdditionalData &data)
:
Solver<VectorType> (cn),
additional_data(data)
{}
template <class VectorType>
SolverRichardson<VectorType>::~SolverRichardson()
{}
template <class VectorType>
template <typename MatrixType, typename PreconditionerType>
void
SolverRichardson<VectorType>::solve (const MatrixType &A,
VectorType &x,
const VectorType &b,
const PreconditionerType &precondition)
{
SolverControl::State conv=SolverControl::iterate;
double last_criterion = -std::numeric_limits<double>::max();
unsigned int iter = 0;
// Memory allocation
Vr = this->memory.alloc();
VectorType &r = *Vr;
r.reinit(x);
Vd = this->memory.alloc();
VectorType &d = *Vd;
d.reinit(x);
deallog.push("Richardson");
try
{
// Main loop
while (conv==SolverControl::iterate)
{
// Do not use residual,
// but do it in 2 steps
A.vmult(r,x);
r.sadd(-1.,1.,b);
precondition.vmult(d,r);
// The required norm of the
// (preconditioned)
// residual is computed in
// criterion() and stored
// in res.
last_criterion = criterion();
conv = this->iteration_status (iter, last_criterion, x);
if (conv != SolverControl::iterate)
break;
x.add(additional_data.omega,d);
print_vectors(iter,x,r,d);
++iter;
}
}
catch (...)
{
this->memory.free(Vr);
this->memory.free(Vd);
deallog.pop();
throw;
}
// Deallocate Memory
this->memory.free(Vr);
this->memory.free(Vd);
deallog.pop();
// in case of failure: throw exception
if (conv != SolverControl::success)
AssertThrow(false, SolverControl::NoConvergence (iter,
last_criterion));
// otherwise exit as normal
}
template <class VectorType>
template <typename MatrixType, typename PreconditionerType>
void
SolverRichardson<VectorType>::Tsolve (const MatrixType &A,
VectorType &x,
const VectorType &b,
const PreconditionerType &precondition)
{
SolverControl::State conv=SolverControl::iterate;
double last_criterion = -std::numeric_limits<double>::max();
unsigned int iter = 0;
// Memory allocation
Vr = this->memory.alloc();
VectorType &r = *Vr;
r.reinit(x);
Vd =this-> memory.alloc();
VectorType &d = *Vd;
d.reinit(x);
deallog.push("RichardsonT");
try
{
// Main loop
while (conv==SolverControl::iterate)
{
// Do not use Tresidual,
// but do it in 2 steps
A.Tvmult(r,x);
r.sadd(-1.,1.,b);
precondition.Tvmult(d,r);
last_criterion = criterion();
conv = this->iteration_status (iter, last_criterion, x);
if (conv != SolverControl::iterate)
break;
x.add(additional_data.omega,d);
print_vectors(iter,x,r,d);
++iter;
}
}
catch (...)
{
this->memory.free(Vr);
this->memory.free(Vd);
deallog.pop();
throw;
}
// Deallocate Memory
this->memory.free(Vr);
this->memory.free(Vd);
deallog.pop();
// in case of failure: throw exception
if (conv != SolverControl::success)
AssertThrow(false, SolverControl::NoConvergence (iter, last_criterion));
// otherwise exit as normal
}
template <class VectorType>
void
SolverRichardson<VectorType>::print_vectors(const unsigned int,
const VectorType &,
const VectorType &,
const VectorType &) const
{}
template <class VectorType>
inline typename VectorType::value_type
SolverRichardson<VectorType>::criterion()
{
if (!additional_data.use_preconditioned_residual)
res = Vr->l2_norm();
else
res = Vd->l2_norm();
return res;
}
template <class VectorType>
inline void
SolverRichardson<VectorType>::set_omega (const double om)
{
additional_data.omega=om;
}
#endif // DOXYGEN
DEAL_II_NAMESPACE_CLOSE
#endif
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