/*
 * @BEGIN LICENSE
 *
 * Psi4: an open-source quantum chemistry software package
 *
 * Copyright (c) 2007-2019 The Psi4 Developers.
 *
 * The copyrights for code used from other parties are included in
 * the corresponding files.
 *
 * This file is part of Psi4.
 *
 * Psi4 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, version 3.
 *
 * Psi4 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 Psi4; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * @END LICENSE
 */

/*! \file
    \ingroup DPD
    \brief Enter brief description of file here
*/
#include <cstdio>
#include "dpd.h"

namespace psi {

/* dpd_buf4_symm2(): Symmetrizes two dpdbuf4's by
** taking, I'(pq,rs) = 1/2 [I1(pq,rs) + I2(pq,rs)] (note the
** indices!).  Users should keep in mind that the first! buffer will
** be overwritten when this function is called.  Also note that this
** routine will NOT check to see if the row and column dimensions of
** the input buffers are identical, which is necessary for this to
** work.
**
** Arguments:
**   dpdbuf4 *Buf1: A pointer to the left dpdbuf4 to be symmetrized.
**   dpdbuf4 *Buf2: A pointer to the right dpdbuf4 to be symmetrized.  */

int DPD::buf4_symm2(dpdbuf4 *Buf1, dpdbuf4 *Buf2) {
    int h, row, col, all_buf_irrep;
    double value;

    all_buf_irrep = Buf1->file.my_irrep;

    for (h = 0; h < Buf1->params->nirreps; h++) {
        buf4_mat_irrep_init(Buf1, h);
        buf4_mat_irrep_rd(Buf1, h);

        buf4_mat_irrep_init(Buf2, h);
        buf4_mat_irrep_rd(Buf2, h);

        for (row = 0; row < Buf1->params->rowtot[h]; row++)
            for (col = 0; col < Buf1->params->coltot[h ^ all_buf_irrep]; col++) {
                value = 0.5 * (Buf1->matrix[h][row][col] + Buf2->matrix[h][col][row]);
                Buf1->matrix[h][row][col] = value;
            }

        buf4_mat_irrep_wrt(Buf1, h);
        buf4_mat_irrep_close(Buf1, h);
        buf4_mat_irrep_close(Buf2, h);
    }

    return 0;
}

}  // namespace psi
