Preconditioner.h

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/******************************************************************************
 * Copyright (c) 2021.                                                        *
 * The Regents of the University of Michigan and DFT-EFE developers.          *
 *                                                                            *
 * This file is part of the DFT-EFE code.                                     *
 *                                                                            *
 * DFT-EFE is free software: you can redistribute it and/or modify            *
 *   it under the terms of the Lesser GNU General Public License as           *
 *   published by the Free Software Foundation, either version 3 of           *
 *   the License, or (at your option) any later version.                      *
 *                                                                            *
 * DFT-EFE is distributed in the hope that it will be useful, but             *
 *   WITHOUT ANY WARRANTY; without even the implied warranty                  *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                     *
 *   See the Lesser GNU General Public License for more details.              *
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 * You should have received a copy of the GNU Lesser General Public           *
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 *   <https://www.gnu.org/licenses/>.                                         *
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/*
 * @author Bikash Kanungo
 */
 
#ifndef dftefePreconditioner_h
#define dftefePreconditioner_h
 
#include <utils/MemorySpaceType.h>
#include <linearAlgebra/OperatorContext.h>
#include <linearAlgebra/Vector.h>
#include <linearAlgebra/MultiVector.h>
#include <linearAlgebra/LinearAlgebraTypes.h>
#include <linearAlgebra/BlasLapackTypedef.h>
namespace dftefe
{
  namespace linearAlgebra
  {
    template <typename ValueTypeOperator,
              typename ValueTypeOperand,
              utils::MemorySpace memorySpace>
    class Preconditioner
      : public OperatorContext<ValueTypeOperator, ValueTypeOperand, memorySpace>
    {
      //
      // typedefs
      //
    public:
      //
      // alias to define the union of ValueTypeOperator and ValueTypeOperand
      // (e.g., the union of double and complex<double> is complex<double>)
      //
      using ValueTypeUnion =
        blasLapack::scalar_type<ValueTypeOperator, ValueTypeOperand>;
 
    public:
      ~Preconditioner() = default;
 
      /*
       * @brief Function to apply the pre-conditoner on an input Vector \p x
       * and store the output in \p y. A typical use case is that the
       * pre-conditioner is a matrix (\f$A$\f) and we want to evaluate
       * \f$y=Ax$\f
       *
       * @param[in] x Input Vector
       * @param[out] y Output Vector that stores the action of the operator
       *  on \p x
       *
       * @note The input Vector \p x can be modified inside the function for
       * performance reasons. If the user needs \p x to be constant
       * (un-modified), we suggest the user to make a copy of \p x
       * prior to calling this function
       *
       */
      // virtual void
      // apply(Vector<ValueTypeOperand, memorySpace> &x,
      //       Vector<ValueTypeUnion, memorySpace> &  y) const = 0;
 
      /*
       * @brief Function to apply the pre-conditoner on an input Vector \p X
       * and store the output in \p Y. A typical use case is that the
       * pre-conditioner is a matrix (\f$A$\f) and we want to evaluate
       * \f$Y=AX$\f
       *
       * @param[in] X Input Vector
       * @param[out] Y Output Vector that stores the action of the operator
       *  on \p X
       *
       * @note The input Vector \p X can be modified inside the function for
       * performance reasons. If the user needs \p X to be constant
       * (un-modified), we suggest the user to make a copy of \p X
       * prior to calling this function
       *
       */
      virtual void
      apply(MultiVector<ValueTypeOperand, memorySpace> &X,
            MultiVector<ValueTypeUnion, memorySpace> &  Y) const = 0;
 
      virtual PreconditionerType
      getPreconditionerType() const = 0;
    };
  } // end of namespace linearAlgebra
} // end of namespace dftefe
#endif // dftefePreconditioner_h