Lanczos.h

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/*
** This file is part of eOn.
**
** SPDX-License-Identifier: BSD-3-Clause
**
** Copyright (c) 2010--present, eOn Development Team
** All rights reserved.
**
** Repo:
** https://github.com/TheochemUI/eOn
*/
#pragma once
#include "Eigen.h"
#include "EonLogger.h"
 
#include "LowestEigenmode.h"
#include "Matter.h"
#include "Parameters.h"
 
namespace eonc {
 
// Lanczos method to find the lowest curvature mode.
// Default Krylov space = all free atoms ([Lanczos] phva_atoms = All).
// Optional mobile list (or phva_atoms) is the PHVA active set: free/fixed is
// the optimizer mask and is not redefined.
class Lanczos : public LowestEigenmode {
 
public:
  Lanczos(std::shared_ptr<Matter> matter, const Parameters &params,
          std::shared_ptr<Potential> pot);
  ~Lanczos() = default;
  void compute(std::shared_ptr<Matter> matter,
               AtomMatrix initialDirection) override;
  void compute(std::shared_ptr<Matter> matter, AtomMatrix initialDirection,
               const VectorXi &mobileAtoms);
  double getEigenvalue() override;
  AtomMatrix getEigenvector() override;
 
private:
  AtomMatrix lowestEv;
  double lowestEw{0.0};
  eonc::log::Scoped log;
};
 
} // namespace eonc