aepbalance.h

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////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1994-2025 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>
 
OCTAVE_BEGIN_NAMESPACE(octave)
 
OCTAVE_BEGIN_NAMESPACE(math)
 
template <typename MT>
class aepbalance
{
public:
 
  typedef typename MT::real_column_vector_type VT;
 
  aepbalance () : m_balanced_mat (), m_scale (), m_ilo (), m_ihi (), m_job () { }
 
  OCTAVE_API aepbalance (const MT& a, bool noperm = false, bool noscal = false);
 
  aepbalance (const aepbalance& a)
    : m_balanced_mat (a.m_balanced_mat), m_scale (a.m_scale),
      m_ilo(a.m_ilo), m_ihi(a.m_ihi), m_job(a.m_job)
  { }
 
  aepbalance& operator = (const aepbalance& a)
  {
    if (this != &a)
      {
        m_balanced_mat = a.m_balanced_mat;
        m_scale = a.m_scale;
        m_ilo = a.m_ilo;
        m_ihi = a.m_ihi;
        m_job = a.m_job;
      }
 
    return *this;
  }
 
  virtual ~aepbalance () = default;
 
  OCTAVE_API MT balancing_matrix () const;
 
  MT balanced_matrix () const
  {
    return m_balanced_mat;
  }
 
  VT permuting_vector () const
  {
    octave_idx_type n = m_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 >= m_ihi; i--)
      {
        octave_idx_type j = m_scale(i) - 1;
        std::swap (pv(i), pv(j));
      }
 
    for (octave_idx_type i = 0; i < m_ilo-1; i++)
      {
        octave_idx_type j = m_scale(i) - 1;
        std::swap (pv(i), pv(j));
      }
 
    return pv;
  }
 
  VT scaling_vector () const
  {
    octave_idx_type n = m_balanced_mat.rows ();
 
    VT scv (n);
 
    for (octave_idx_type i = 0; i < m_ilo-1; i++)
      scv(i) = 1;
 
    for (octave_idx_type i = m_ilo-1; i < m_ihi; i++)
      scv(i) = m_scale(i);
 
    for (octave_idx_type i = m_ihi; i < n; i++)
      scv(i) = 1;
 
    return scv;
  }
 
protected:
 
  MT m_balanced_mat;
  VT m_scale;
  octave_idx_type m_ilo;
  octave_idx_type m_ihi;
  char m_job;
};
 
OCTAVE_END_NAMESPACE(math)
OCTAVE_END_NAMESPACE(octave)
 
#endif