chebyshevOrthogonalizedSubspaceIterationSolver.h

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// ---------------------------------------------------------------------
//
// Copyright (c) 2017-2025 The Regents of the University of Michigan and DFT-FE
// authors.
//
// This file is part of the DFT-FE code.
//
// The DFT-FE code is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the DFT-FE distribution.
//
// ---------------------------------------------------------------------
//
 
 
#ifndef chebyshevOrthogonalizedSubspaceIterationSolver_h
#define chebyshevOrthogonalizedSubspaceIterationSolver_h
 
#include "dftParameters.h"
#include "eigenSolver.h"
#include "operator.h"
#include "elpaScalaManager.h"
#include "dftParameters.h"
#include "BLASWrapper.h"
 
namespace dftfe
{
  /**
   * @brief Concrete class implementing Chebyshev filtered orthogonalized subspace
   * iteration solver.
   * @author Phani Motamarri, Sambit Das
   */
 
  class chebyshevOrthogonalizedSubspaceIterationSolver : public eigenSolverClass
  {
  public:
    /**
     * @brief Constructor.
     *
     * @param mpi_comm_parent parent mpi communicator
     * @param mpi_comm_domain domain decomposition mpi communicator
     * @param lowerBoundWantedSpectrum Lower Bound of the Wanted Spectrum.
     * @param lowerBoundUnWantedSpectrum Lower Bound of the UnWanted Spectrum.
     */
    chebyshevOrthogonalizedSubspaceIterationSolver(
      const MPI_Comm &     mpi_comm_parent,
      const MPI_Comm &     mpi_comm_domain,
      double               lowerBoundWantedSpectrum,
      double               lowerBoundUnWantedSpectrum,
      double               upperBoundUnWantedSpectrum,
      const dftParameters &dftParams);
 
 
    /**
     * @brief Destructor.
     */
    ~chebyshevOrthogonalizedSubspaceIterationSolver();
 
 
    /**
     * @brief Solve a generalized eigen problem.
     */
    void
    solve(operatorDFTClass<dftfe::utils::MemorySpace::HOST> &operatorMatrix,
          std::shared_ptr<
            dftfe::linearAlgebra::BLASWrapper<dftfe::utils::MemorySpace::HOST>>
            &                  BLASWrapperPtr,
          elpaScalaManager &   elpaScala,
          dataTypes::number *  eigenVectorsFlattened,
          const unsigned int   totalNumberWaveFunctions,
          const unsigned int   localVectorSize,
          std::vector<double> &eigenValues,
          std::vector<double> &residuals,
          const MPI_Comm &     interBandGroupComm,
          const MPI_Comm &     mpiCommDomain,
          const bool           isFirstFilteringCall,
          const bool           computeResidual,
          const bool           useMixedPrec = false,
          const bool           isFirstScf   = false);
 
    /**
     * @brief Solve a generalized eigen problem.
     */
    void
    solve(operatorDFTClass<dftfe::utils::MemorySpace::HOST> &operatorMatrix,
          std::vector<distributedCPUVec<double>> &           eigenVectors,
          std::vector<double> &                              eigenValues,
          std::vector<double> &                              residuals);
 
    /**
     * @brief reinit spectrum bounds
     */
    void
    reinitSpectrumBounds(double lowerBoundWantedSpectrum,
                         double lowerBoundUnWantedSpectrum,
                         double upperBoundUnWantedSpectrum);
 
  private:
    const MPI_Comm d_mpiCommParent;
    //
    // stores lower bound of wanted spectrum
    //
    double d_lowerBoundWantedSpectrum;
 
    //
    // stores lower bound of unwanted spectrum
    //
    double d_lowerBoundUnWantedSpectrum;
 
 
    //
    // stores upper bound of unwanted spectrum
    //
    double d_upperBoundUnWantedSpectrum;
 
 
    const dftParameters &d_dftParams;
 
    //
    // variables for printing out and timing
    //
    dealii::ConditionalOStream pcout;
    dealii::TimerOutput        computing_timer;
  };
} // namespace dftfe
#endif