solver_bicgstab.h

Go to the documentation of this file.

// ---------------------------------------------------------------------
//
// Copyright (C) 1998 - 2020 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.md at
// the top level directory of deal.II.
//
// ---------------------------------------------------------------------
 
#ifndef dealii_solver_bicgstab_h
#define dealii_solver_bicgstab_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/logstream.h>
#include <deal.II/base/signaling_nan.h>
#include <deal.II/base/subscriptor.h>
 
#include <deal.II/lac/solver.h>
#include <deal.II/lac/solver_control.h>
 
#include <cmath>
 
DEAL_II_NAMESPACE_OPEN
 
 
namespace internal
{
  class SolverBicgstabData
  {
  protected:
    double alpha;
    double beta;
    double omega;
    double rho;
    double rhobar;
 
    unsigned int step;
 
    double res;
 
    SolverBicgstabData();
  };
} // namespace internal
 
template <typename VectorType = Vector<double>>
class SolverBicgstab : public SolverBase<VectorType>,
                       protected internal::SolverBicgstabData
{
public:
  struct AdditionalData
  {
    explicit AdditionalData(
      const bool   exact_residual = true,
      const double breakdown =
        std::numeric_limits<typename VectorType::value_type>::min())
      : exact_residual(exact_residual)
      , breakdown(breakdown)
    {}
    bool exact_residual;
    double breakdown;
  };
 
  SolverBicgstab(SolverControl &           cn,
                 VectorMemory<VectorType> &mem,
                 const AdditionalData &    data = AdditionalData());
 
  SolverBicgstab(SolverControl &       cn,
                 const AdditionalData &data = AdditionalData());
 
  virtual ~SolverBicgstab() override = default;
 
  template <typename MatrixType, typename PreconditionerType>
  void
  solve(const MatrixType &        A,
        VectorType &              x,
        const VectorType &        b,
        const PreconditionerType &preconditioner);
 
protected:
  VectorType *Vx;
 
  typename VectorMemory<VectorType>::Pointer Vr;
 
  typename VectorMemory<VectorType>::Pointer Vrbar;
 
  typename VectorMemory<VectorType>::Pointer Vp;
 
  typename VectorMemory<VectorType>::Pointer Vy;
 
  typename VectorMemory<VectorType>::Pointer Vz;
 
  typename VectorMemory<VectorType>::Pointer Vt;
 
  typename VectorMemory<VectorType>::Pointer Vv;
 
  const VectorType *Vb;
 
  template <typename MatrixType>
  double
  criterion(const MatrixType &A, const VectorType &x, const VectorType &b);
 
  virtual void
  print_vectors(const unsigned int step,
                const VectorType & x,
                const VectorType & r,
                const VectorType & d) const;
 
  AdditionalData additional_data;
 
private:
  struct IterationResult
  {
    bool                 breakdown;
    SolverControl::State state;
    unsigned int         last_step;
    double               last_residual;
 
    IterationResult(const bool                 breakdown,
                    const SolverControl::State state,
                    const unsigned int         last_step,
                    const double               last_residual);
  };
 
  template <typename MatrixType, typename PreconditionerType>
  IterationResult
  iterate(const MatrixType &A, const PreconditionerType &preconditioner);
};
 
/*-------------------------Inline functions -------------------------------*/
 
#ifndef DOXYGEN
 
 
template <typename VectorType>
SolverBicgstab<VectorType>::IterationResult::IterationResult(
  const bool                 breakdown,
  const SolverControl::State state,
  const unsigned int         last_step,
  const double               last_residual)
  : breakdown(breakdown)
  , state(state)
  , last_step(last_step)
  , last_residual(last_residual)
{}
 
 
 
template <typename VectorType>
SolverBicgstab<VectorType>::SolverBicgstab(SolverControl &           cn,
                                           VectorMemory<VectorType> &mem,
                                           const AdditionalData &    data)
  : SolverBase<VectorType>(cn, mem)
  , Vx(nullptr)
  , Vb(nullptr)
  , additional_data(data)
{}
 
 
 
template <typename VectorType>
SolverBicgstab<VectorType>::SolverBicgstab(SolverControl &       cn,
                                           const AdditionalData &data)
  : SolverBase<VectorType>(cn)
  , Vx(nullptr)
  , Vb(nullptr)
  , additional_data(data)
{}
 
 
 
template <typename VectorType>
template <typename MatrixType>
double
SolverBicgstab<VectorType>::criterion(const MatrixType &A,
                                      const VectorType &x,
                                      const VectorType &b)
{
  A.vmult(*Vt, x);
  Vt->add(-1., b);
  res = Vt->l2_norm();
 
  return res;
}
 
 
 
template <typename VectorType>
void
SolverBicgstab<VectorType>::print_vectors(const unsigned int,
                                          const VectorType &,
                                          const VectorType &,
                                          const VectorType &) const
{}
 
 
 
template <typename VectorType>
template <typename MatrixType, typename PreconditionerType>
typename SolverBicgstab<VectorType>::IterationResult
SolverBicgstab<VectorType>::iterate(const MatrixType &        A,
                                    const PreconditionerType &preconditioner)
{
  A.vmult(*Vr, *Vx);
  Vr->sadd(-1., 1., *Vb);
  res = Vr->l2_norm();
 
  SolverControl::State state = this->iteration_status(step, res, *Vx);
  if (state == SolverControl::State::success)
    return IterationResult(false, state, step, res);
 
  alpha = omega = rho = 1.;
 
  VectorType &r    = *Vr;
  VectorType &rbar = *Vrbar;
  VectorType &p    = *Vp;
  VectorType &y    = *Vy;
  VectorType &z    = *Vz;
  VectorType &t    = *Vt;
  VectorType &v    = *Vv;
 
  rbar         = r;
  bool startup = true;
 
  do
    {
      ++step;
 
      rhobar = r * rbar;
      if (std::fabs(rhobar) < additional_data.breakdown)
        {
          return IterationResult(true, state, step, res);
        }
      beta = rhobar * alpha / (rho * omega);
      rho  = rhobar;
      if (startup == true)
        {
          p       = r;
          startup = false;
        }
      else
        {
          p.sadd(beta, 1., r);
          p.add(-beta * omega, v);
        }
 
      preconditioner.vmult(y, p);
      A.vmult(v, y);
      rhobar = rbar * v;
      if (std::fabs(rhobar) < additional_data.breakdown)
        {
          return IterationResult(true, state, step, res);
        }
 
      alpha = rho / rhobar;
 
      res = std::sqrt(r.add_and_dot(-alpha, v, r));
 
      // check for early success, see the lac/bicgstab_early testcase as to
      // why this is necessary
      //
      // note: the vector *Vx we pass to the iteration_status signal here is
      // only the current approximation, not the one we will return with, which
      // will be x=*Vx + alpha*y
      if (this->iteration_status(step, res, *Vx) == SolverControl::success)
        {
          Vx->add(alpha, y);
          print_vectors(step, *Vx, r, y);
          return IterationResult(false, SolverControl::success, step, res);
        }
 
      preconditioner.vmult(z, r);
      A.vmult(t, z);
      rhobar         = t * r;
      auto t_squared = t * t;
      if (t_squared < additional_data.breakdown)
        {
          return IterationResult(true, state, step, res);
        }
      omega = rhobar / (t * t);
      Vx->add(alpha, y, omega, z);
 
      if (additional_data.exact_residual)
        {
          r.add(-omega, t);
          res = criterion(A, *Vx, *Vb);
        }
      else
        res = std::sqrt(r.add_and_dot(-omega, t, r));
 
      state = this->iteration_status(step, res, *Vx);
      print_vectors(step, *Vx, r, y);
    }
  while (state == SolverControl::iterate);
 
  return IterationResult(false, state, step, res);
}
 
 
 
template <typename VectorType>
template <typename MatrixType, typename PreconditionerType>
void
SolverBicgstab<VectorType>::solve(const MatrixType &        A,
                                  VectorType &              x,
                                  const VectorType &        b,
                                  const PreconditionerType &preconditioner)
{
  LogStream::Prefix prefix("Bicgstab");
 
  // Allocate temporary memory.
  Vr    = typename VectorMemory<VectorType>::Pointer(this->memory);
  Vrbar = typename VectorMemory<VectorType>::Pointer(this->memory);
  Vp    = typename VectorMemory<VectorType>::Pointer(this->memory);
  Vy    = typename VectorMemory<VectorType>::Pointer(this->memory);
  Vz    = typename VectorMemory<VectorType>::Pointer(this->memory);
  Vt    = typename VectorMemory<VectorType>::Pointer(this->memory);
  Vv    = typename VectorMemory<VectorType>::Pointer(this->memory);
 
  Vr->reinit(x, true);
  Vrbar->reinit(x, true);
  Vp->reinit(x, true);
  Vy->reinit(x, true);
  Vz->reinit(x, true);
  Vt->reinit(x, true);
  Vv->reinit(x, true);
 
  Vx = &x;
  Vb = &b;
 
  step = 0;
 
  IterationResult state(false, SolverControl::failure, 0, 0);
  do
    {
      state = iterate(A, preconditioner);
    }
  while (state.state == SolverControl::iterate);
 
 
  // Release the temporary memory again.
  Vr.reset();
  Vrbar.reset();
  Vp.reset();
  Vy.reset();
  Vz.reset();
  Vt.reset();
  Vv.reset();
 
  // In case of failure: throw exception
  AssertThrow(state.state == SolverControl::success,
              SolverControl::NoConvergence(state.last_step,
                                           state.last_residual));
  // Otherwise exit as normal
}
 
#endif // DOXYGEN
 
DEAL_II_NAMESPACE_CLOSE
 
#endif