exact_pole_sums.h

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/*
 *            Copyright 2009-2026 The VOTCA Development Team
 *                       (http://www.votca.org)
 *
 *      Licensed under the Apache License, Version 2.0 (the "License")
 *
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *              http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
 
#pragma once
#ifndef VOTCA_XTP_EXACT_POLE_SUMS_H
#define VOTCA_XTP_EXACT_POLE_SUMS_H
 
// Local VOTCA includes
#include "eigen.h"
 
namespace votca {
namespace xtp {

struct ExactPoles {
  const Eigen::VectorXd& energies;  // e_m, size B
  Index n_occ;
  const Eigen::VectorXd& omegas;  // Omega_s, size S
  double eta;
 
  Index nlevels() const { return energies.size(); }
  Index nmodes() const { return omegas.size(); }
  Index npoles() const { return nlevels() * nmodes(); }
};
 
namespace exact_pole_sums {

double Value(const ExactPoles& poles, const double* residues, double w);

double Derivative(const ExactPoles& poles, const double* residues, double w);

Eigen::VectorXd Values(const ExactPoles& poles, const double* residues,
                       const Eigen::VectorXd& w);

Eigen::VectorXd Values(const ExactPoles& poles, const double* residues,
                       const Eigen::VectorXd& w, const double* mode_factors);

Eigen::VectorXd ValuesDirect(const ExactPoles& poles, const double* residues,
                             const Eigen::VectorXd& w);
Eigen::VectorXd ValuesDirect(const ExactPoles& poles, const double* residues,
                             const Eigen::VectorXd& w,
                             const double* mode_factors);

Eigen::VectorXd ValuesDirectWeighted(const ExactPoles& poles,
                                     const double* weights,
                                     const Eigen::VectorXd& w);

Eigen::MatrixXd OffDiagonal(const ExactPoles& poles,
                            const Eigen::MatrixXd& residues_all,
                            const Eigen::VectorXd& w);
 
}  // namespace exact_pole_sums
}  // namespace xtp
}  // namespace votca
 
#endif  // VOTCA_XTP_EXACT_POLE_SUMS_H