PadeApproximator.h

/* Copyright 2018 Kristofer Björnson
 *
 * 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.
 */


#ifndef COM_DAFER45_TBTK_PADE_APPROXIMATOR
#define COM_DAFER45_TBTK_PADE_APPROXIMATOR

#include "TBTK/Polynomial.h"
#include "TBTK/TBTKMacros.h"

#include <complex>
#include <vector>

namespace TBTK{

class PadeApproximator{
public:
    void setNumeratorDegree(unsigned int numeratorDegree);

    void setDenominatorDegree(unsigned int denominatorDegree);

    std::vector<
        Polynomial<std::complex<double>, std::complex<double>, int>
    > approximate(
        const std::vector<std::complex<double>> &values,
        const std::vector<std::complex<double>> &arguments
    );
private:
    unsigned int numeratorDegree;

    unsigned int denominatorDegree;

    void executeLeastSquare(
        std::complex<double> *matrix,
        std::complex<double> *vector,
        unsigned int numRows,
        unsigned int numColumns
    );
};

inline void PadeApproximator::setNumeratorDegree(unsigned int numeratorDegree){
    this->numeratorDegree = numeratorDegree;
}

inline void PadeApproximator::setDenominatorDegree(
    unsigned int denominatorDegree
){
    this->denominatorDegree = denominatorDegree;
}

}; //End of namespace TBTK

#endif