KohnShamEigenSolver.h

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 * Copyright (c) 2021.                                                        *
 * The Regents of the University of Michigan and DFT-EFE developers.          *
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 *   See the Lesser GNU General Public License for more details.              *
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/*
 * @author Avirup Sircar
 */
 
#ifndef dftefeKohnShamEigenSolver_h
#define dftefeKohnShamEigenSolver_h
 
#include <utils/MemorySpaceType.h>
#include <linearAlgebra/BlasLapackTypedef.h>
#include <linearAlgebra/LinAlgOpContext.h>
#include <linearAlgebra/MultiVector.h>
#include <linearAlgebra/OperatorContext.h>
#include <linearAlgebra/ChebyshevFilteredEigenSolver.h>
#include <linearAlgebra/HermitianIterativeEigenSolver.h>
#include <memory>
#include <utils/ConditionalOStream.h>
#include <utils/Profiler.h>
 
namespace dftefe
{
  namespace ksdft
  {
    template <typename ValueTypeOperator,
              typename ValueTypeOperand,
              utils::MemorySpace memorySpace>
    class KohnShamEigenSolver
      : public linearAlgebra::HermitianIterativeEigenSolver<ValueTypeOperator,
                                                            ValueTypeOperand,
                                                            memorySpace>
    {
    public:
      using ValueType = typename linearAlgebra::HermitianIterativeEigenSolver<
        ValueTypeOperator,
        ValueTypeOperand,
        memorySpace>::ValueType;
      using RealType = typename linearAlgebra::HermitianIterativeEigenSolver<
        ValueTypeOperator,
        ValueTypeOperand,
        memorySpace>::RealType;
      using OpContext = typename linearAlgebra::HermitianIterativeEigenSolver<
        ValueTypeOperator,
        ValueTypeOperand,
        memorySpace>::OpContext;
 
    public:
      KohnShamEigenSolver(
        const size_type numElectrons,
        const double    smearingTemperature,
        const double    fermiEnergyTolerance,
        const double    fracOccupancyTolerance,
        const double    eigenSolveResidualTolerance,
        const size_type maxChebyshevFilterPass,
        linearAlgebra::MultiVector<ValueTypeOperand, memorySpace>
          &waveFunctionSubspaceGuess,
        linearAlgebra::Vector<ValueTypeOperand, memorySpace> &lanczosGuess,
        const linearAlgebra::ElpaScalapackManager &           elpaScala,
        bool             isResidualChebyshevFilter = true,
        const size_type  waveFunctionBatchSize     = 0,
        const OpContext &MLanczos =
          linearAlgebra::IdentityOperatorContext<ValueTypeOperator,
                                                 ValueTypeOperand,
                                                 memorySpace>(),
        const OpContext &MInvLanczos =
          linearAlgebra::IdentityOperatorContext<ValueTypeOperator,
                                                 ValueTypeOperand,
                                                 memorySpace>(),
        linearAlgebra::OrthogonalizationType orthoType =
          linearAlgebra::OrthogonalizationType::CHOLESKY_GRAMSCHMIDT,
        bool storeIntermediateSubspaces = false);
 
      ~KohnShamEigenSolver() = default;
 
      void
      reinitBasis(
        linearAlgebra::MultiVector<ValueTypeOperand, memorySpace>
          &waveFunctionSubspaceGuess,
        linearAlgebra::Vector<ValueTypeOperand, memorySpace> &lanczosGuess,
        const OpContext &                                     MLanczos =
          linearAlgebra::IdentityOperatorContext<ValueTypeOperator,
                                                 ValueTypeOperand,
                                                 memorySpace>(),
        const OpContext &MInvLanczos =
          linearAlgebra::IdentityOperatorContext<ValueTypeOperator,
                                                 ValueTypeOperand,
                                                 memorySpace>());
 
      void
      reinitBounds(double wantedSpectrumLowerBound,
                   double wantedSpectrumUpperBound);
 
      RealType
      getFermiEnergy();
 
      std::vector<RealType>
      getFractionalOccupancy();
 
      std::vector<RealType>
      getEigenSolveResidualNorm();
 
      void
      setChebyPolyScalingFactor(double scalingFactor);
 
      void
      setChebyshevPolynomialDegree(size_type chebyPolyDeg);
 
      void
      setResidualChebyshevFilterFlag(bool flag);
 
      linearAlgebra::EigenSolverError
      solve(const OpContext &      kohnShamOperator,
            std::vector<RealType> &kohnShamEnergies,
            linearAlgebra::MultiVector<ValueType, memorySpace>
              &              kohnShamWaveFunctions,
            bool             computeWaveFunctions = false,
            const OpContext &M =
              linearAlgebra::IdentityOperatorContext<ValueTypeOperator,
                                                     ValueTypeOperand,
                                                     memorySpace>(),
            const OpContext &MInv =
              linearAlgebra::IdentityOperatorContext<ValueTypeOperator,
                                                     ValueTypeOperand,
                                                     memorySpace>()) override;
 
      linearAlgebra::MultiVector<ValueType, memorySpace> &
      getFilteredSubspace();
 
      linearAlgebra::MultiVector<ValueType, memorySpace> &
      getOrthogonalizedFilteredSubspace();
 
    private:
      std::vector<double>
      getLinearEigenSolveResidual(
        const OpContext &kohnShamOperator,
        const linearAlgebra::MultiVector<ValueType, memorySpace>
          &              kohnShamWaveFunctions,
        const OpContext &M);
 
      double    d_smearingTemperature;
      double    d_fermiEnergyTolerance;
      double    d_fracOccupancyTolerance;
      double    d_eigenSolveResidualTolerance;
      size_type d_maxChebyshevFilterPass;
      size_type d_chebyshevPolynomialDegree;
      size_type d_numWantedEigenvalues;
      size_type d_waveFunctionBatchSize;
      linearAlgebra::MultiVector<ValueTypeOperand, memorySpace>
        *d_waveFunctionSubspaceGuess;
      linearAlgebra::Vector<ValueTypeOperand, memorySpace> *d_lanczosGuess;
      const OpContext *                                     d_MLanczos;
      const OpContext *                                     d_MInvLanczos;
      std::vector<RealType>                                 d_fracOccupancy;
      std::vector<RealType>                                 d_eigSolveResNorm;
      RealType                                              d_fermiEnergy;
      bool                                                  d_isSolved;
      const size_type                                       d_numElectrons;
      utils::ConditionalOStream                             d_rootCout;
      double d_wantedSpectrumLowerBound;
      double d_wantedSpectrumUpperBound;
      bool   d_isBoundKnown;
      double d_chebyPolyScalingFactor;
      bool   d_setChebyPolDegExternally;
 
      std::shared_ptr<
        linearAlgebra::ChebyshevFilteredEigenSolver<ValueTypeOperator,
                                                    ValueTypeOperand,
                                                    memorySpace>>
        d_chfsi;
 
      linearAlgebra::MultiVector<ValueType, memorySpace>
        *d_filteredSubspaceOrtho;
      linearAlgebra::MultiVector<ValueType, memorySpace> *d_filteredSubspace;
      utils::Profiler                                     d_p;
      bool       d_isResidualChebyFilter;
      const bool d_storeIntermediateSubspaces;
 
      size_type d_batchSizeSmall;
      std::shared_ptr<linearAlgebra::MultiVector<ValueType, memorySpace>>
        d_waveFnBatch, d_HXBatch, d_MXBatch, d_waveFnBatchSmall, d_HXBatchSmall,
        d_MXBatchSmall;
      utils::MemoryStorage<ValueType, memorySpace> d_kohnShamEnergiesMemspace,
        d_nOnes;
 
      linearAlgebra::OrthogonalizationType       d_orthoType;
      const linearAlgebra::ElpaScalapackManager *d_elpaScala;
 
    }; // end of class KohnShamEigenSolver
  }    // namespace ksdft
} // end of namespace dftefe
#include <ksdft/KohnShamEigenSolver.t.cpp>
#endif // dftefeKohnShamEigenSolver_h