LanczosExtremeEigenSolver.h

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 * Copyright (c) 2021.                                                        *
 * The Regents of the University of Michigan and DFT-EFE developers.          *
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 * This file is part of the DFT-EFE code.                                     *
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 * DFT-EFE is free software: you can redistribute it and/or modify            *
 *   it under the terms of the Lesser GNU General Public License as           *
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 *   See the Lesser GNU General Public License for more details.              *
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/*
 * @author Avirup Sircar
 */
 
#ifndef dftefeLanczosExtremeEigenSolver_h
#define dftefeLanczosExtremeEigenSolver_h
 
#include <utils/MemorySpaceType.h>
#include <linearAlgebra/BlasLapackTypedef.h>
#include <linearAlgebra/LinAlgOpContext.h>
#include <linearAlgebra/Vector.h>
#include <linearAlgebra/MultiVector.h>
#include <linearAlgebra/OperatorContext.h>
#include <linearAlgebra/IdentityOperatorContext.h>
#include <linearAlgebra/HermitianIterativeEigenSolver.h>
#include <memory>
 
namespace dftefe
{
  namespace linearAlgebra
  {
    template <typename ValueTypeOperator,
              typename ValueTypeOperand,
              utils::MemorySpace memorySpace>
    class LanczosExtremeEigenSolver
      : public HermitianIterativeEigenSolver<ValueTypeOperator,
                                             ValueTypeOperand,
                                             memorySpace>
    {
    public:
      using ValueType =
        blasLapack::scalar_type<ValueTypeOperator, ValueTypeOperand>;
      using RealType = blasLapack::real_type<ValueType>;
      using OpContext =
        typename HermitianIterativeEigenSolver<ValueTypeOperator,
                                               ValueTypeOperand,
                                               memorySpace>::OpContext;
 
      LanczosExtremeEigenSolver(
        const size_type                              maxKrylovSubspaceSize,
        const size_type                              numLowerExtermeEigenValues,
        const size_type                              numUpperExtermeEigenValues,
        std::vector<double> &                        tolerance,
        double                                       lanczosBetaTolerance,
        const Vector<ValueTypeOperand, memorySpace> &initialGuess,
        bool                                         isAdaptiveSolve = true);
 
      LanczosExtremeEigenSolver(
        const size_type      maxKrylovSubspaceSize,
        const size_type      numLowerExtermeEigenValues,
        const size_type      numUpperExtermeEigenValues,
        std::vector<double> &tolerance,
        double               lanczosBetaTolerance,
        std::shared_ptr<const utils::mpi::MPIPatternP2P<memorySpace>>
                                                      mpiPatternP2P,
        std::shared_ptr<LinAlgOpContext<memorySpace>> linAlgOpContext,
        bool                                          isAdaptiveSolve = true);
 
      ~LanczosExtremeEigenSolver() = default;
 
      void
      reinit(const size_type      maxKrylovSubspaceSize,
             const size_type      numLowerExtermeEigenValues,
             const size_type      numUpperExtermeEigenValues,
             std::vector<double> &tolerance,
             double               lanczosBetaTolerance,
             const Vector<ValueTypeOperand, memorySpace> &initialGuess);
 
      void
      reinit(const size_type      maxKrylovSubspaceSize,
             const size_type      numLowerExtermeEigenValues,
             const size_type      numUpperExtermeEigenValues,
             std::vector<double> &tolerance,
             double               lanczosBetaTolerance,
             std::shared_ptr<const utils::mpi::MPIPatternP2P<memorySpace>>
                                                           mpiPatternP2P,
             std::shared_ptr<LinAlgOpContext<memorySpace>> linAlgOpContext);
 
      EigenSolverError
      solve(const OpContext &                    A,
            std::vector<RealType> &              eigenValues,
            MultiVector<ValueType, memorySpace> &eigenVectors,
            bool                                 computeEigenVectors = false,
            const OpContext &B = IdentityOperatorContext<ValueTypeOperator,
                                                         ValueTypeOperand,
                                                         memorySpace>(),
            const OpContext &BInv =
              IdentityOperatorContext<ValueTypeOperator,
                                      ValueTypeOperand,
                                      memorySpace>()) override;
 
      void
      getTridiagonalMatrix(std::vector<RealType> &diagonal,
                           std::vector<RealType> &subDiagonal) const;
 
    private:
      Vector<ValueTypeOperand, memorySpace> d_initialGuess;
      size_type                             d_maxKrylovSubspaceSize;
      size_type                             d_numLowerExtermeEigenValues;
      size_type                             d_numUpperExtermeEigenValues;
      std::vector<double>                   d_tolerance;
      double                                d_lanczosBetaTolerance;
      std::vector<RealType>                 d_diagonal;
      std::vector<RealType>                 d_subDiagonal;
      bool                                  d_isSolved;
      const bool                            d_isAdaptiveSolve;
 
 
    }; // end of class LanczosExtremeEigenSolver
  }    // namespace linearAlgebra
} // end of namespace dftefe
#include <linearAlgebra/LanczosExtremeEigenSolver.t.cpp>
#endif // dftefeLanczosExtremeEigenSolver_h