text: /* ************************************************************************
   * Copyright (c) 2018-2020 Advanced Micro Devices, Inc.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   *
   * ************************************************************************ */
  
  #ifndef ROCALUTION_KRYLOV_FCG_HPP_
  #define ROCALUTION_KRYLOV_FCG_HPP_
  
  #include "../solver.hpp"
  
  #include <vector>
  
  namespace rocalution
  {
  
      /** \ingroup solver_module
    * \class FCG
    * \brief Flexible Conjugate Gradient Method
    * \details
    * The Flexible Conjugate Gradient method is an iterative method for solving sparse
    * symmetric positive definite linear systems \f$Ax=b\f$. It is similar to the Conjugate
    * Gradient method with the only difference, that it allows the preconditioner
    * \f$M^{-1}\f$ to be not a constant operator. This can be especially helpful if the
    * operation \f$M^{-1}x\f$ is the result of another iterative process and not a constant
    * operator.
    * \cite fcg
    *
    * \tparam OperatorType - can be LocalMatrix or GlobalMatrix
    * \tparam VectorType - can be LocalVector or GlobalVector
    * \tparam ValueType - can be float, double, std::complex<float> or std::complex<double>
    */
      template <class OperatorType, class VectorType, typename ValueType>
      class FCG : public IterativeLinearSolver<OperatorType, VectorType, ValueType>
      {
      public:
          FCG();
          virtual ~FCG();
  
          virtual void Print(void) const;
  
          virtual void Build(void);
          virtual void ReBuildNumeric(void);
          virtual void Clear(void);
  
      protected:
          virtual void SolveNonPrecond_(const VectorType& rhs, VectorType* x);
          virtual void SolvePrecond_(const VectorType& rhs, VectorType* x);
  
          virtual void PrintStart_(void) const;
          virtual void PrintEnd_(void) const;
  
          virtual void MoveToHostLocalData_(void);
          virtual void MoveToAcceleratorLocalData_(void);
  
      private:
          VectorType r_, w_, z_;
          VectorType p_, q_;
      };
  
  } // namespace rocalution
  
  #endif // ROCALUTION_KRYLOV_FCG_HPP_
  