solver_CG.cpp

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#include "solver_CG.h"


#ifdef USE_FACTORY
namespace {
  Solver *create_object(Fopr *fopr)
  {
    return new Solver_CG(fopr);
  }


  bool init = Solver::Factory::Register("CG", create_object);
}
#endif

//- parameter entries
namespace {
  void append_entry(Parameters& param)
  {
    param.Register_int("maximum_number_of_iteration", 0);
    param.Register_double("convergence_criterion_squared", 0.0);

    param.Register_string("verbose_level", "NULL");
  }


#ifdef USE_PARAMETERS_FACTORY
  bool init_param = ParametersFactory::Register("Solver.CG", append_entry);
#endif
}
//- end

//- parameters class
Parameters_Solver_CG::Parameters_Solver_CG() { append_entry(*this); }
//- end

const std::string Solver_CG::class_name = "Solver_CG";

//====================================================================
void Solver_CG::set_parameters(const Parameters& params)
{
  const string str_vlevel = params.get_string("verbose_level");

  m_vl = vout.set_verbose_level(str_vlevel);

  //- fetch and check input parameters
  int    Niter;
  double Stop_cond;

  int err = 0;
  err += params.fetch_int("maximum_number_of_iteration", Niter);
  err += params.fetch_double("convergence_criterion_squared", Stop_cond);

  if (err) {
    vout.crucial(m_vl, "%s: fetch error, input parameter not found.\n", class_name.c_str());
    exit(EXIT_FAILURE);
  }


  set_parameters(Niter, Stop_cond);
}


//====================================================================
void Solver_CG::set_parameters(const int Niter, const double Stop_cond)
{
  ThreadManager_OpenMP::assert_single_thread(class_name);

  //- print input parameters
  vout.general(m_vl, "Parameters of %s:\n", class_name.c_str());
  vout.general(m_vl, "  Niter     = %d\n", Niter);
  vout.general(m_vl, "  Stop_cond = %16.8e\n", Stop_cond);

  //- range check
  int err = 0;
  err += ParameterCheck::non_negative(Niter);
  err += ParameterCheck::square_non_zero(Stop_cond);

  if (err) {
    vout.crucial(m_vl, "%s: parameter range check failed.\n", class_name.c_str());
    exit(EXIT_FAILURE);
  }

  //- store values
  m_Niter     = Niter;
  m_Stop_cond = Stop_cond;
}


//====================================================================
void Solver_CG::solve(Field& xq, const Field& b,
                      int& Nconv, double& diff)
{
  double bnorm2 = b.norm2();
  double snorm  = 1.0 / bnorm2;
  int    bsize  = b.size();

  vout.paranoiac(m_vl, "%s: solver starts\n", class_name.c_str());
  vout.paranoiac(m_vl, "  norm of b = %16.8e\n", bnorm2);
  vout.paranoiac(m_vl, "  size of b = %d\n", bsize);

  reset_field(b);

  copy(s, b); //  s = b;

  double rr;
  int    Nconv2 = -1;

  solve_init(b, rr);

  bool is_converged = false;

  vout.detailed(m_vl, "    iter: %8d  %22.15e\n", 0, rr * snorm);


  for (int iter = 0; iter < m_Niter; iter++) {
    if (is_converged) break;

    solve_step(rr);

    vout.detailed(m_vl, "    iter: %8d  %22.15e\n", iter + 1, rr * snorm);

    if (rr * snorm < m_Stop_cond) {
      m_fopr->mult(s, x); // s  = m_fopr->mult(x);
      axpy(s, -1.0, b);   // s -= b;

      double diff2 = s.norm2();

      if (diff2 * snorm < m_Stop_cond) {
        Nconv2       = iter + 1;
        is_converged = true;
      } else {
        copy(s, x); // s = x;
        solve_init(b, rr);
      }
    }
  }


  copy(xq, x);        // xq = x;

  m_fopr->mult(p, x); // p  = m_fopr->mult(x);
  axpy(p, -1.0, b);   // p -= b;

  double diff2 = p.norm2();

  if (diff2 * snorm > m_Stop_cond) {
    vout.crucial(m_vl, "%s: not converged.\n", class_name.c_str());
    exit(EXIT_FAILURE);
  }


#pragma omp barrier
#pragma omp master
  {
    diff  = sqrt(diff2);
    Nconv = Nconv2;
  }
#pragma omp barrier
}


//====================================================================
void Solver_CG::reset_field(const Field& b)
{
#pragma omp barrier
#pragma omp master
  {
    int Nin  = b.nin();
    int Nvol = b.nvol();
    int Nex  = b.nex();

    if ((s.nin() != Nin) || (s.nvol() != Nvol) || (s.nex() != Nex)) {
      s.reset(Nin, Nvol, Nex);
      r.reset(Nin, Nvol, Nex);
      x.reset(Nin, Nvol, Nex);
      p.reset(Nin, Nvol, Nex);
    }
  }
#pragma omp barrier

  vout.detailed(m_vl, "    %s: field size reset.\n", class_name.c_str());
}


//====================================================================
void Solver_CG::solve_init(const Field& b, double& rr)
{
  copy(x, s);  // x = s;

  //- r = b - A x
  copy(r, b);          // r = b;
  m_fopr->mult(s, x);  // s  = m_fopr->mult(x);
  axpy(r, -1.0, s);    // r -= s;

  copy(p, r);          // p  = r;
  rr = r.norm2();      // rr = r * r;
}


//====================================================================
void Solver_CG::solve_step(double& rr)
{
  double rr_prev = rr;

  m_fopr->mult(s, p);     // s = m_fopr->mult(p);

  double pap = dot(p, s); // pap  = p * s;
  double cr  = rr_prev / pap;

  axpy(x, cr, p);   // x += cr * p;
  axpy(r, -cr, s);  // r -= cr * s;

  rr = r.norm2();   // rr = r * r;

  double rr_ratio = rr / rr_prev;
  aypx(rr_ratio, p, r);  // p  = (rr / rr_prev) * p + r
}


//====================================================================
//============================================================END=====