////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1994-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
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// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
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////////////////////////////////////////////////////////////////////////

#if ! defined (octave_aepbalance_h)
#define octave_aepbalance_h 1

#include "octave-config.h"

#include <algorithm>

namespace octave
{
  namespace math
  {
    template <typename MT>
    class
    aepbalance
    {
    public:

      typedef typename MT::real_column_vector_type VT;

      aepbalance (void) : balanced_mat (), scale (), ilo (), ihi (), job () { }

      OCTAVE_API aepbalance (const MT& a, bool noperm = false, bool noscal = false);

      aepbalance (const aepbalance& a)
        : balanced_mat (a.balanced_mat), scale (a.scale),
          ilo(a.ilo), ihi(a.ihi), job(a.job)
      { }

      aepbalance& operator = (const aepbalance& a)
      {
        if (this != &a)
          {
            balanced_mat = a.balanced_mat;
            scale = a.scale;
            ilo = a.ilo;
            ihi = a.ihi;
            job = a.job;
          }

        return *this;
      }

      virtual ~aepbalance (void) = default;

      OCTAVE_API MT balancing_matrix (void) const;

      MT balanced_matrix (void) const
      {
        return balanced_mat;
      }

      VT permuting_vector (void) const
      {
        octave_idx_type n = balanced_mat.rows ();

        VT pv (n);

        for (octave_idx_type i = 0; i < n; i++)
          pv(i) = i+1;

        for (octave_idx_type i = n-1; i >= ihi; i--)
          {
            octave_idx_type j = scale(i) - 1;
            std::swap (pv(i), pv(j));
          }

        for (octave_idx_type i = 0; i < ilo-1; i++)
          {
            octave_idx_type j = scale(i) - 1;
            std::swap (pv(i), pv(j));
          }

        return pv;
      }

      VT scaling_vector (void) const
      {
        octave_idx_type n = balanced_mat.rows ();

        VT scv (n);

        for (octave_idx_type i = 0; i < ilo-1; i++)
          scv(i) = 1;

        for (octave_idx_type i = ilo-1; i < ihi; i++)
          scv(i) = scale(i);

        for (octave_idx_type i = ihi; i < n; i++)
          scv(i) = 1;

        return scv;
      }

    protected:

      MT balanced_mat;
      VT scale;
      octave_idx_type ilo;
      octave_idx_type ihi;
      char job;
    };
  }
}

#endif