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/**************************************************************************
**
** Copyright (C) 1993 David E. Steward & Zbigniew Leyk, all rights reserved.
**
** Meschach Library
**
** This Meschach Library is provided "as is" without any express
** or implied warranty of any kind with respect to this software.
** In particular the authors shall not be liable for any direct,
** indirect, special, incidental or consequential damages arising
** in any way from use of the software.
**
** Everyone is granted permission to copy, modify and redistribute this
** Meschach Library, provided:
** 1. All copies contain this copyright notice.
** 2. All modified copies shall carry a notice stating who
** made the last modification and the date of such modification.
** 3. No charge is made for this software or works derived from it.
** This clause shall not be construed as constraining other software
** distributed on the same medium as this software, nor is a
** distribution fee considered a charge.
**
***************************************************************************/
/*
Files for matrix computations
Givens operations file. Contains routines for calculating and
applying givens rotations for/to vectors and also to matrices by
row and by column.
*/
/* givens.c 1.2 11/25/87 */
static char rcsid[] = "$Id: givens.c,v 1.3 1995/03/27 15:41:15 des Exp $";
#include <stdio.h>
#include <math.h>
#include "matrix.h"
#include "matrix2.h"
/* givens -- returns c,s parameters for Givens rotation to
eliminate y in the vector [ x y ]' */
void givens(x,y,c,s)
double x,y;
Real *c,*s;
{
Real norm;
norm = sqrt(x*x+y*y);
if ( norm == 0.0 )
{ *c = 1.0; *s = 0.0; } /* identity */
else
{ *c = x/norm; *s = y/norm; }
}
/* rot_vec -- apply Givens rotation to x's i & k components */
VEC *rot_vec(x,i,k,c,s,out)
VEC *x,*out;
u_int i,k;
double c,s;
{
Real temp;
if ( x==VNULL )
error(E_NULL,"rot_vec");
if ( i >= x->dim || k >= x->dim )
error(E_RANGE,"rot_vec");
out = v_copy(x,out);
/* temp = c*out->ve[i] + s*out->ve[k]; */
temp = c*v_entry(out,i) + s*v_entry(out,k);
/* out->ve[k] = -s*out->ve[i] + c*out->ve[k]; */
v_set_val(out,k,-s*v_entry(out,i)+c*v_entry(out,k));
/* out->ve[i] = temp; */
v_set_val(out,i,temp);
return (out);
}
/* rot_rows -- premultiply mat by givens rotation described by c,s */
MAT *rot_rows(mat,i,k,c,s,out)
MAT *mat,*out;
u_int i,k;
double c,s;
{
u_int j;
Real temp;
if ( mat==(MAT *)NULL )
error(E_NULL,"rot_rows");
if ( i >= mat->m || k >= mat->m )
error(E_RANGE,"rot_rows");
if ( mat != out )
out = m_copy(mat,m_resize(out,mat->m,mat->n));
for ( j=0; j<mat->n; j++ )
{
/* temp = c*out->me[i][j] + s*out->me[k][j]; */
temp = c*m_entry(out,i,j) + s*m_entry(out,k,j);
/* out->me[k][j] = -s*out->me[i][j] + c*out->me[k][j]; */
m_set_val(out,k,j, -s*m_entry(out,i,j) + c*m_entry(out,k,j));
/* out->me[i][j] = temp; */
m_set_val(out,i,j, temp);
}
return (out);
}
/* rot_cols -- postmultiply mat by givens rotation described by c,s */
MAT *rot_cols(mat,i,k,c,s,out)
MAT *mat,*out;
u_int i,k;
double c,s;
{
u_int j;
Real temp;
if ( mat==(MAT *)NULL )
error(E_NULL,"rot_cols");
if ( i >= mat->n || k >= mat->n )
error(E_RANGE,"rot_cols");
if ( mat != out )
out = m_copy(mat,m_resize(out,mat->m,mat->n));
for ( j=0; j<mat->m; j++ )
{
/* temp = c*out->me[j][i] + s*out->me[j][k]; */
temp = c*m_entry(out,j,i) + s*m_entry(out,j,k);
/* out->me[j][k] = -s*out->me[j][i] + c*out->me[j][k]; */
m_set_val(out,j,k, -s*m_entry(out,j,i) + c*m_entry(out,j,k));
/* out->me[j][i] = temp; */
m_set_val(out,j,i,temp);
}
return (out);
}
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