matrix_trace.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 <tensor/tensor.h>

namespace tensor {

  template<typename n>
  static const n do_trace(const Tensor<n> &t)
  {
    n output = number_zero<n>();
    const index r = t.rows();
    const index c = t.columns();
    typename Tensor<n>::const_iterator it = t.begin();
    for (index j = std::min(r,c); j--; it += (r+1)) {
      output += *it;
    }
    return output;
  }

} // namespace tensor