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/* eigen/eigen_sort.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
*
* This program 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 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
* 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.
*/
/* Author: G. Jungman, Modified: B. Gough. */
#include <config.h>
#include <stdlib.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_eigen.h>
#include <gsl/gsl_complex.h>
#include <gsl/gsl_complex_math.h>
/* The eigen_sort below is not very good, but it is simple and
* self-contained. We can always implement an improved sort later. */
int
gsl_eigen_symmv_sort (gsl_vector * eval, gsl_matrix * evec,
gsl_eigen_sort_t sort_type)
{
if (evec->size1 != evec->size2)
{
GSL_ERROR ("eigenvector matrix must be square", GSL_ENOTSQR);
}
else if (eval->size != evec->size1)
{
GSL_ERROR ("eigenvalues must match eigenvector matrix", GSL_EBADLEN);
}
else
{
const size_t N = eval->size;
size_t i;
for (i = 0; i < N - 1; i++)
{
size_t j;
size_t k = i;
double ek = gsl_vector_get (eval, i);
/* search for something to swap */
for (j = i + 1; j < N; j++)
{
int test;
const double ej = gsl_vector_get (eval, j);
switch (sort_type)
{
case GSL_EIGEN_SORT_VAL_ASC:
test = (ej < ek);
break;
case GSL_EIGEN_SORT_VAL_DESC:
test = (ej > ek);
break;
case GSL_EIGEN_SORT_ABS_ASC:
test = (fabs (ej) < fabs (ek));
break;
case GSL_EIGEN_SORT_ABS_DESC:
test = (fabs (ej) > fabs (ek));
break;
default:
GSL_ERROR ("unrecognized sort type", GSL_EINVAL);
}
if (test)
{
k = j;
ek = ej;
}
}
if (k != i)
{
/* swap eigenvalues */
gsl_vector_swap_elements (eval, i, k);
/* swap eigenvectors */
gsl_matrix_swap_columns (evec, i, k);
}
}
return GSL_SUCCESS;
}
}
int
gsl_eigen_hermv_sort (gsl_vector * eval, gsl_matrix_complex * evec,
gsl_eigen_sort_t sort_type)
{
if (evec->size1 != evec->size2)
{
GSL_ERROR ("eigenvector matrix must be square", GSL_ENOTSQR);
}
else if (eval->size != evec->size1)
{
GSL_ERROR ("eigenvalues must match eigenvector matrix", GSL_EBADLEN);
}
else
{
const size_t N = eval->size;
size_t i;
for (i = 0; i < N - 1; i++)
{
size_t j;
size_t k = i;
double ek = gsl_vector_get (eval, i);
/* search for something to swap */
for (j = i + 1; j < N; j++)
{
int test;
const double ej = gsl_vector_get (eval, j);
switch (sort_type)
{
case GSL_EIGEN_SORT_VAL_ASC:
test = (ej < ek);
break;
case GSL_EIGEN_SORT_VAL_DESC:
test = (ej > ek);
break;
case GSL_EIGEN_SORT_ABS_ASC:
test = (fabs (ej) < fabs (ek));
break;
case GSL_EIGEN_SORT_ABS_DESC:
test = (fabs (ej) > fabs (ek));
break;
default:
GSL_ERROR ("unrecognized sort type", GSL_EINVAL);
}
if (test)
{
k = j;
ek = ej;
}
}
if (k != i)
{
/* swap eigenvalues */
gsl_vector_swap_elements (eval, i, k);
/* swap eigenvectors */
gsl_matrix_complex_swap_columns (evec, i, k);
}
}
return GSL_SUCCESS;
}
}
int
gsl_eigen_nonsymmv_sort (gsl_vector_complex * eval,
gsl_matrix_complex * evec,
gsl_eigen_sort_t sort_type)
{
if (evec->size1 != evec->size2)
{
GSL_ERROR ("eigenvector matrix must be square", GSL_ENOTSQR);
}
else if (eval->size != evec->size1)
{
GSL_ERROR ("eigenvalues must match eigenvector matrix", GSL_EBADLEN);
}
else
{
const size_t N = eval->size;
size_t i;
for (i = 0; i < N - 1; i++)
{
size_t j;
size_t k = i;
gsl_complex ek = gsl_vector_complex_get (eval, i);
/* search for something to swap */
for (j = i + 1; j < N; j++)
{
int test;
const gsl_complex ej = gsl_vector_complex_get (eval, j);
switch (sort_type)
{
case GSL_EIGEN_SORT_ABS_ASC:
test = (gsl_complex_abs (ej) < gsl_complex_abs (ek));
break;
case GSL_EIGEN_SORT_ABS_DESC:
test = (gsl_complex_abs (ej) > gsl_complex_abs (ek));
break;
case GSL_EIGEN_SORT_VAL_ASC:
case GSL_EIGEN_SORT_VAL_DESC:
default:
GSL_ERROR ("invalid sort type", GSL_EINVAL);
}
if (test)
{
k = j;
ek = ej;
}
}
if (k != i)
{
/* swap eigenvalues */
gsl_vector_complex_swap_elements (eval, i, k);
/* swap eigenvectors */
gsl_matrix_complex_swap_columns (evec, i, k);
}
}
return GSL_SUCCESS;
}
}
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