/* -*- c++ -*- (enables emacs c++ mode) */
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// This file is a modified version of cg.h from ITL.
// See http://osl.iu.edu/research/itl/
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/**@file gmm_solver_cg.h
   @author  Andrew Lumsdaine <lums@osl.iu.edu>
   @author  Lie-Quan Lee <llee@osl.iu.edu>
   @author  Yves Renard <Yves.Renard@insa-lyon.fr>
   @date October 13, 2002.
   @brief Conjugate gradient iterative solver. 
*/
#ifndef GMM_SOLVER_CG_H__
#define GMM_SOLVER_CG_H__

#include "gmm_kernel.h"
#include "gmm_iter.h"

namespace gmm {

  /* ******************************************************************** */
  /*		conjugate gradient                           		  */
  /* (preconditionned, with parametrable additional scalar product)       */
  /* ******************************************************************** */

  template <typename Matrix, typename Matps, typename Precond, 
            typename Vector1, typename Vector2>
  void cg(const Matrix& A, Vector1& x, const Vector2& b, const Matps& PS,
	  const Precond &P, iteration &iter) {

    typedef typename temporary_dense_vector<Vector1>::vector_type temp_vector;
    typedef typename linalg_traits<Vector1>::value_type T;

    T rho, rho_1(0), a;
    temp_vector p(vect_size(x)), q(vect_size(x)), r(vect_size(x)),
      z(vect_size(x));
    iter.set_rhsnorm(gmm::sqrt(gmm::abs(vect_hp(PS, b, b))));

    if (iter.get_rhsnorm() == 0.0)
      clear(x);
    else {
      mult(A, scaled(x, T(-1)), b, r);
      mult(P, r, z);
      rho = vect_hp(PS, z, r);
      copy(z, p);

      while (!iter.finished_vect(r)) {

	if (!iter.first()) { 
	  mult(P, r, z);
	  rho = vect_hp(PS, z, r);
	  add(z, scaled(p, rho / rho_1), p);
	}
	mult(A, p, q);

	a = rho / vect_hp(PS, q, p);	
	add(scaled(p, a), x);
	add(scaled(q, -a), r);
	rho_1 = rho;

	++iter;
      }
    }
  }

  template <typename Matrix, typename Matps, typename Precond, 
            typename Vector1, typename Vector2>
  void cg(const Matrix& A, Vector1& x, const Vector2& b, const Matps& PS,
	  const gmm::identity_matrix &, iteration &iter) {

    typedef typename temporary_dense_vector<Vector1>::vector_type temp_vector;
    typedef typename linalg_traits<Vector1>::value_type T;

    T rho, rho_1(0), a;
    temp_vector p(vect_size(x)), q(vect_size(x)), r(vect_size(x));
    iter.set_rhsnorm(gmm::sqrt(gmm::abs(vect_hp(PS, b, b))));

    if (iter.get_rhsnorm() == 0.0)
      clear(x);
    else {
      mult(A, scaled(x, T(-1)), b, r);
      rho = vect_hp(PS, r, r);
      copy(r, p);

      while (!iter.finished_vect(r)) {

	if (!iter.first()) { 
	  rho = vect_hp(PS, r, r);
	  add(r, scaled(p, rho / rho_1), p);
	}	
	mult(A, p, q);
	a = rho / vect_hp(PS, q, p);	
	add(scaled(p, a), x);
	add(scaled(q, -a), r);
	rho_1 = rho;
	++iter;
      }
    }
  }

  template <typename Matrix, typename Matps, typename Precond, 
            typename Vector1, typename Vector2> inline 
  void cg(const Matrix& A, const Vector1& x, const Vector2& b, const Matps& PS,
	 const Precond &P, iteration &iter)
  { cg(A, linalg_const_cast(x), b, PS, P, iter); }

  template <typename Matrix, typename Precond, 
            typename Vector1, typename Vector2> inline
  void cg(const Matrix& A, Vector1& x, const Vector2& b,
	 const Precond &P, iteration &iter)
  { cg(A, x , b, identity_matrix(), P, iter); }

  template <typename Matrix, typename Precond, 
            typename Vector1, typename Vector2> inline
  void cg(const Matrix& A, const Vector1& x, const Vector2& b,
	 const Precond &P, iteration &iter)
  { cg(A, x , b , identity_matrix(), P , iter); }

}


#endif //  GMM_SOLVER_CG_H__
