TwoElectronIntegralBuffer.hpp

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// This file is part of GQCG-GQCP.
//
// Copyright (C) 2017-2020  the GQCG developers
//
// GQCG-GQCP is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// GQCG-GQCP is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with GQCG-GQCP.  If not, see <http://www.gnu.org/licenses/>.
 
#pragma once
 
 
#include "Basis/Integrals/BaseTwoElectronIntegralBuffer.hpp"
 
#include <array>
 
 
namespace GQCP {
 
 
template <typename _IntegralScalar, size_t _N>
class TwoElectronIntegralBuffer:
    public BaseTwoElectronIntegralBuffer<_IntegralScalar, _N> {
public:
    // The scalar representation of an integral.
    using IntegralScalar = _IntegralScalar;
 
    // The number of components the corresponding operator has.
    static constexpr auto N = _N;
 
 
protected:
    // The calculated integrals.
    std::array<std::vector<IntegralScalar>, N> buffer;
 
 
public:
    /*
     *  MARK: Constructors
     */
 
    TwoElectronIntegralBuffer(const size_t nbf1, const size_t nbf2, const size_t nbf3, const size_t nbf4, const std::array<std::vector<IntegralScalar>, N>& buffer) :
        buffer {buffer},
        BaseTwoElectronIntegralBuffer<IntegralScalar, N>(nbf1, nbf2, nbf3, nbf4) {}
 
 
    /*
     *  MARK: Emplacement
     */
 
    bool areIntegralsAllZero() const override { return false; }
 
    IntegralScalar value(const size_t i, const size_t f1, const size_t f2, const size_t f3, const size_t f4) const override {
        // We'll access the component first, then a row-major ordering of the calculated integrals.
        return this->buffer[i][f4 + this->nbf4 * (f3 + this->nbf3 * (f2 + this->nbf2 * f1))];
    }
};
 
 
}  // namespace GQCP