chargeresponse.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_CHARGERESPONSE_H
#define VOTCA_XTP_CHARGERESPONSE_H
 
// Standard includes
#include <string>
#include <vector>
 
// Local VOTCA includes
#include "checkpoint.h"
#include "eigen.h"
 
namespace votca {
namespace xtp {

class ChargeResponse {
 public:
  ChargeResponse() = default;
  ChargeResponse(std::vector<std::string> elements, Eigen::MatrixXd pi);

  void LoadFromFile(const std::string& filename);
 
  bool empty() const { return pi_.size() == 0; }
  Index size() const { return Index(pi_.rows()); }
  const Eigen::MatrixXd& Pi() const { return pi_; }
  const std::vector<std::string>& Elements() const { return elements_; }

  ChargeResponse Permuted(const std::vector<Index>& order) const;
 
  void WriteToCpt(CheckpointWriter& w) const;
  void ReadFromCpt(CheckpointReader& r);
 
 private:
  // Throws unless pi_ is square, matches elements_, symmetric, charge
  // conserving and positive semidefinite to a relative tolerance; then
  // removes the rounding of the file (symmetrizes and projects onto the
  // charge-conserving vectors).
  void Check(const std::string& source);
 
  std::vector<std::string> elements_;
  Eigen::MatrixXd pi_;
};
 
}  // namespace xtp
}  // namespace votca
 
#endif  // VOTCA_XTP_CHARGERESPONSE_H