STK_Givens.h

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/*--------------------------------------------------------------------*/
/*     Copyright (C) 2004-2007  Serge Iovleff

    This program 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; 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this program; if not, write to the
    Free Software Foundation, Inc.,
    59 Temple Place,
    Suite 330,
    Boston, MA 02111-1307
    USA

    Contact : Serge.Iovleff@stkpp.org
*/

/*
 * Project:  Algebra
 * Purpose:  Define Givens rotation methods for Algebra classes.
 * Author:   Serge Iovleff, serge.iovleff@stkpp.org
 *
 **/

#ifndef STK_GIVENS_H
#define STK_GIVENS_H

#include "../../STKernel/include/STK_Real.h"
#include "../../Sdk/include/STK_ITContainer2D.h"

namespace STK
{
Real compGivens( Real const& y
               , Real const& z
               , Real& cosinus
               , Real& sinus
               );

template < class TContainer2D>
void rightGivens( ITContainer2D< Real, TContainer2D>& M
                , Integer const& col1
                , Integer const& col2
                , Real const& cosinus
                , Real const& sinus
                )
{
  const Integer first = M.firstRow(), last = M.lastRow();
  // Apply givens rotation
  for (Integer i = first; i <=last; i++)
  {
    const Real aux1 = M(i, col1), aux2 = M(i, col2);
    M(i, col1) = cosinus * aux1 + sinus * aux2;
    M(i, col2) = cosinus * aux2 - sinus * aux1;
  }
}

template < class TContainer2D>
void leftGivens( ITContainer2D< Real, TContainer2D>& M
               , Integer const& row1
               , Integer const& row2
               , Real const& cosinus
               , Real const& sinus
               )
{
  const Integer first = M.firstCol(), last = M.lastCol();
  // apply left Givens rotation
  for (Integer j = first; j<= last; j++)
  {
    const Real aux1 = M(row1, j), aux2 = M(row2, j);
    M(row1, j) = cosinus * aux1 + sinus * aux2;
    M(row2, j) = cosinus * aux2 - sinus * aux1;
  }
}

} // namespace STK

#endif /*STK_GIVENS_H*/