eigs_sym_sp_d.cc

// -*- mode: c++; fill-column: 80; c-basic-offset: 2; indent-tabs-mode: nil -*-
/*
    Copyright (c) 2010 Juan Jose Garcia Ripoll

    Tensor is free software; you can redistribute it and/or modify it
    under the terms of the GNU Library General Public License as published
    by the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program 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 Library General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include <linalg.h>
#include <arpack.h>

RTensor
eigs_sym(const RSparse &A, RArpack::EigType t, size_t neig, RTensor *eigenvectors,
         const RTensor::elt_t *initial_guess)
{
    size_t n = A.columns();
#ifdef COMPLEX
    size_t ndouble = 2*n;
#else
    size_t ndouble = n;
#endif

    if (n <= 10) {
        return eigs_sym(full(A), t, neig, eigenvectors, initial_guess);
    }

    if (A.rows() != n) {
        std::cerr << "In eigs(): Can only compute eigenvalues of square matrices.";
        myabort();
    }

    RArpack data(ndouble, t, neig);

    if (initial_guess)
        data.set_start_vector((const double *)initial_guess);

    size_t bytes = ndouble * sizeof(double);
    while (data.update() < RArpack::Finished) {
        RTensor x(n, (RTensor::elt_t *)data.get_x_vector());
        RTensor y = mmult(A, x);
        memcpy(data.get_y_vector(), (const double *)x.pointer(), bytes);
    }
    if (data.get_status() == RArpack::Finished) {
        if (eigenvectors) {
            *eigenvectors = RTensor(n, neig);
        }
        return data.get_data((double *)eigenvectors->pointer());
    } else {
        std::cerr << data.error_message() << '\n';
        myabort();
    }
    return RTensor();
}