LibintOneElectronIntegralBuffer.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/BaseOneElectronIntegralBuffer.hpp"
#include "Basis/Integrals/Interfaces/LibintInterfacer.hpp"
 
 
namespace GQCP {
 
 
template <size_t _N>
class LibintOneElectronIntegralBuffer: public BaseOneElectronIntegralBuffer<double, _N> {
public:
    using IntegralScalar = double;  // the scalar representation of an integral for libint is always a real number
    static constexpr auto N = _N;   // the number of components the operator has
 
 
private:
    size_t component_offset;  // the number of libint components that should be skipped during access of calculated values (libint2::Operator::emultipole1 has 4 libint2 components, but in reality there should only be 1)
    double scaling_factor;    // a factor that is multiplied to all of the calculated integrals
 
    using libint2_buffer_t = LibintInterfacer::libint_target_ptr_vec;  // t for type
    libint2_buffer_t libint2_buffer;
 
 
public:
    /*
     *  CONSTRUCTORS
     */
 
    LibintOneElectronIntegralBuffer(const libint2_buffer_t& libint2_buffer, const size_t nbf1, const size_t nbf2, const size_t component_offset = 0, const double scaling_factor = 1.0) :
        libint2_buffer {libint2_buffer},
        component_offset {component_offset},
        scaling_factor {scaling_factor},
        BaseOneElectronIntegralBuffer<IntegralScalar, N>(nbf1, nbf2) {}
 
 
    bool areIntegralsAllZero() const override { return (this->libint2_buffer[0] == nullptr); }
 
    IntegralScalar value(const size_t i, const size_t f1, const size_t f2) const override {
        return this->scaling_factor * this->libint2_buffer[i + this->component_offset][f2 + f1 * this->nbf2];  // integrals are packed in row-major form
    }
};
 
 
}  // namespace GQCP