scaledsolve.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_SCALEDSOLVE_H
#define VOTCA_XTP_SCALEDSOLVE_H
 
// Local VOTCA includes
#include "eigen.h"
 
namespace votca {
namespace xtp {

template <class IterativeSolver>
Eigen::VectorXd ScaledSolve(const IterativeSolver& solver,
                            const Eigen::VectorXd& b, bool* solved = nullptr) {
  const double scale = b.size() > 0 ? b.cwiseAbs().maxCoeff() : 0.0;
  if (solved != nullptr) {
    *solved = scale > 0.0;
  }
  if (!(scale > 0.0)) {
    return Eigen::VectorXd::Zero(b.size());
  }
  Eigen::VectorXd x = solver.solve(b / scale);
  return x * scale;
}
 
}  // namespace xtp
}  // namespace votca
 
#endif  // VOTCA_XTP_SCALEDSOLVE_H