//@HEADER
// ************************************************************************
//
//                 Belos: Block Linear Solvers Package
//                  Copyright 2004 Sandia Corporation
//
// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
// the U.S. Government retains certain rights in this software.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// 3. Neither the name of the Corporation nor the names of the
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SANDIA CORPORATION OR THE
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Questions? Contact Michael A. Heroux (maherou@sandia.gov)
//
// ************************************************************************
//@HEADER

#ifndef BELOS_CG_ITERATION_HPP
#define BELOS_CG_ITERATION_HPP

/*! \file BelosCGIteration.hpp
    \brief Pure virtual base class which augments the basic interface for a conjugate gradient linear solver iteration.
*/

#include "BelosConfigDefs.hpp"
#include "BelosTypes.hpp"
#include "BelosIteration.hpp"

namespace Belos {

  //! @name CGIteration Structures 
  //@{ 
  
  /** \brief Structure to contain pointers to CGIteration state variables.
   *
   * This struct is utilized by CGIteration::initialize() and CGIteration::getState().
   */
  template <class ScalarType, class MV>
  struct CGIterationState {

    /*! \brief The current residual. */
    Teuchos::RCP<const MV> R;

    /*! \brief The current preconditioned residual. */
    Teuchos::RCP<const MV> Z;

    /*! \brief The current decent direction vector */
    Teuchos::RCP<const MV> P;

    /*! \brief The matrix A applied to current decent direction vector */
    Teuchos::RCP<const MV> AP;
    
    CGIterationState() : R(Teuchos::null), Z(Teuchos::null), 
		    P(Teuchos::null), AP(Teuchos::null)
    {}
  };

  //! @name CGIteration Exceptions
  //@{ 
  
  /** \brief CGIterationInitFailure is thrown when the CGIteration object is unable to
   * generate an initial iterate in the CGIteration::initialize() routine. 
   *
   * This std::exception is thrown from the CGIteration::initialize() method, which is
   * called by the user or from the CGIteration::iterate() method if isInitialized()
   * == \c false.
   *
   * In the case that this std::exception is thrown, 
   * CGIteration::isInitialized() will be \c false and the user will need to provide
   * a new initial iterate to the iteration.
   */
  class CGIterationInitFailure : public BelosError {public:
    CGIterationInitFailure(const std::string& what_arg) : BelosError(what_arg)
    {}};

  /** \brief CGIterateFailure is thrown when the CGIteration object is unable to
   * compute the next iterate in the CGIteration::iterate() routine. 
   *
   * This std::exception is thrown from the CGIteration::iterate() method.
   *
   */
  class CGIterateFailure : public BelosError {public:
    CGIterateFailure(const std::string& what_arg) : BelosError(what_arg)
    {}};
  
  /** \brief CGIterationOrthoFailure is thrown when the CGIteration object is unable to
   * compute independent direction vectors in the CGIteration::iterate() routine. 
   *
   * This std::exception is thrown from the CGIteration::iterate() method.
   *
   */
  class CGIterationOrthoFailure : public BelosError {public:
    CGIterationOrthoFailure(const std::string& what_arg) : BelosError(what_arg)
    {}};

  /** \brief CGIterationLAPACKFailure is thrown when a nonzero return value is passed back
   * from an LAPACK routine.
   *
   * This std::exception is thrown from the CGIteration::iterate() method.
   *
   */
  class CGIterationLAPACKFailure : public BelosError {public:
    CGIterationLAPACKFailure(const std::string& what_arg) : BelosError(what_arg)
    {}};
  
  //@}


template<class ScalarType, class MV, class OP>
class CGIteration : virtual public Iteration<ScalarType,MV,OP> {

  public:

  //! @name State methods
  //@{ 
  /*! \brief Initialize the solver to an iterate, providing a complete state.
   *
   * The %CGIteration contains a certain amount of state, consisting of the current 
   * residual, preconditioned residual, and decent direction.
   *
   * initialize() gives the user the opportunity to manually set these,
   * although only the current unpreconditioned residual is required.
   *
   * \post 
   * <li>isInitialized() == \c true (see post-conditions of isInitialize())
   *
   * \note For any pointer in \c newstate which directly points to the multivectors in 
   * the solver, the data is not copied.
   */
  virtual void initializeCG(CGIterationState<ScalarType,MV>& newstate) = 0;

  /*! \brief Get the current state of the linear solver.
   *
   * The data is only valid if isInitialized() == \c true.
   *
   * \returns A CGIterationState object containing const pointers to the current solver state.
   */
  virtual CGIterationState<ScalarType,MV> getState() const = 0;
  //@}

};

} // end Belos namespace

#endif /* BELOS_CG_ITERATION_HPP */
