MatsubaraSusceptibilityCalculator.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_MATSUBARA_SUSCEPTIBILITY_CALCULATOR
#define COM_DAFER45_TBTK_MATSUBARA_SUSCEPTIBILITY_CALCULATOR

#include "TBTK/RPA/SusceptibilityCalculator.h"

#include <complex>

//#include <omp.h>

namespace TBTK{

class MatsubaraSusceptibilityCalculator : public SusceptibilityCalculator{
public:
    MatsubaraSusceptibilityCalculator(
        const RPA::MomentumSpaceContext &momentumSpaceContext
    );

    ~MatsubaraSusceptibilityCalculator();

    MatsubaraSusceptibilityCalculator* createSlave();

    std::complex<double> calculateSusceptibility(
        const std::vector<double> &k,
        const std::vector<int> &orbitalIndices,
        std::complex<double> energy
    );

    std::vector<std::complex<double>> calculateSusceptibility(
        const DualIndex &kDual,
        const std::vector<int> &orbitalIndices
    );

    void setNumSummationEnergies(unsigned int numSummationEnergies);
private:
    std::complex<double> *greensFunction;

    std::vector<std::complex<double>> summationEnergies;

    MatsubaraSusceptibilityCalculator(
        const RPA::MomentumSpaceContext &momentumSpaceContext,
        int *kPlusQLookupTable
    );

    std::complex<double> calculateSusceptibilityMatsubara(
        const std::vector<double> &k,
        const std::vector<int> &orbitalIndices,
        std::complex<double> energy
    );

    template<bool useKPlusQLookupTable>
    std::vector<std::complex<double>> calculateSusceptibilityMatsubara(
        const DualIndex &kDual,
        const std::vector<int> &orbitalIndices
    );

    void calculateGreensFunction();

    std::complex<double>& getGreensFunctionValue(
        unsigned int meshPoint,
        unsigned int orbital0,
        unsigned int orbital1,
        unsigned int energy,
        unsigned int numEnergies,
        unsigned int numOrbitals
    );
};

inline void MatsubaraSusceptibilityCalculator::setNumSummationEnergies(
    unsigned int numSummationEnergies
){
    TBTKAssert(
        numSummationEnergies%2 == 1,
        "MatsubaraSusceptibilityCalculator::setNumSummationEnergies()",
        "The number of summation energies must be an odd number.",
        ""
    );

    double temperature
        = UnitHandler::convertNaturalToBase<Quantity::Temperature>(
            getMomentumSpaceContext().getModel().getTemperature()
        );
    double kT = UnitHandler::getConstantInBaseUnits("k_B")*temperature;
    double hbar = UnitHandler::getConstantInBaseUnits("hbar");

    summationEnergies.clear();
    for(unsigned int n = 0; n < numSummationEnergies; n++){
        summationEnergies.push_back(
            M_PI*(2*(n - numSummationEnergies/2))*kT/hbar
        );
    }

    clearCache();
    if(greensFunction != nullptr){
        delete [] greensFunction;
        greensFunction = nullptr;
    }
}

/*inline std::vector<std::complex<double>> SusceptibilityCalculator::calculateSusceptibility(
        const std::vector<double> &k,
        const std::vector<int> &orbitalIndices
){
    return calculateSusceptibility(
        DualIndex(
            momentumSpaceContext->getKIndex(k),
            k
        ),
        orbitalIndices
    );
}*/

inline std::complex<double>& MatsubaraSusceptibilityCalculator::getGreensFunctionValue(
    unsigned int meshPoint,
    unsigned int orbital0,
    unsigned int orbital1,
    unsigned int energy,
    unsigned int numEnergies,
    unsigned int numOrbitals
){
    return greensFunction[
        numEnergies*(
            numOrbitals*(numOrbitals*meshPoint + orbital0)
            + orbital1
        ) + energy
    ];
}

};  //End of namespace TBTK

#endif