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/* permutation/permute_source.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
*
* 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 3 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.
*/
/* In-place Permutations
permute: OUT[i] = IN[perm[i]] i = 0 .. N-1
invpermute: OUT[perm[i]] = IN[i] i = 0 .. N-1
PERM is an index map, i.e. a vector which contains a permutation of
the integers 0 .. N-1.
From Knuth "Sorting and Searching", Volume 3 (3rd ed), Section 5.2
Exercise 10 (answers), p 617
FIXME: these have not been fully tested.
*/
int
TYPE (gsl_permute) (const size_t * p, ATOMIC * data, const size_t stride, const size_t n)
{
size_t i, k, pk;
for (i = 0; i < n; i++)
{
k = p[i];
while (k > i)
k = p[k];
if (k < i)
continue ;
/* Now have k == i, i.e the least in its cycle */
pk = p[k];
if (pk == i)
continue ;
/* shuffle the elements of the cycle */
{
unsigned int a;
ATOMIC t[MULTIPLICITY];
for (a = 0; a < MULTIPLICITY; a++)
t[a] = data[i*stride*MULTIPLICITY + a];
while (pk != i)
{
for (a = 0; a < MULTIPLICITY; a++)
{
ATOMIC r1 = data[pk*stride*MULTIPLICITY + a];
data[k*stride*MULTIPLICITY + a] = r1;
}
k = pk;
pk = p[k];
};
for (a = 0; a < MULTIPLICITY; a++)
data[k*stride*MULTIPLICITY + a] = t[a];
}
}
return GSL_SUCCESS;
}
int
FUNCTION (gsl_permute,inverse) (const size_t * p, ATOMIC * data, const size_t stride, const size_t n)
{
size_t i, k, pk;
for (i = 0; i < n; i++)
{
k = p[i];
while (k > i)
k = p[k];
if (k < i)
continue ;
/* Now have k == i, i.e the least in its cycle */
pk = p[k];
if (pk == i)
continue ;
/* shuffle the elements of the cycle in the inverse direction */
{
unsigned int a;
ATOMIC t[MULTIPLICITY];
for (a = 0; a < MULTIPLICITY; a++)
t[a] = data[k*stride*MULTIPLICITY+a];
while (pk != i)
{
for (a = 0; a < MULTIPLICITY; a++)
{
ATOMIC r1 = data[pk*stride*MULTIPLICITY + a];
data[pk*stride*MULTIPLICITY + a] = t[a];
t[a] = r1;
}
k = pk;
pk = p[k];
};
for (a = 0; a < MULTIPLICITY; a++)
data[pk*stride*MULTIPLICITY+a] = t[a];
}
}
return GSL_SUCCESS;
}
int
TYPE (gsl_permute_vector) (const gsl_permutation * p, TYPE (gsl_vector) * v)
{
if (v->size != p->size)
{
GSL_ERROR ("vector and permutation must be the same length", GSL_EBADLEN);
}
TYPE (gsl_permute) (p->data, v->data, v->stride, v->size) ;
return GSL_SUCCESS;
}
int
FUNCTION (gsl_permute_vector,inverse) (const gsl_permutation * p, TYPE (gsl_vector) * v)
{
if (v->size != p->size)
{
GSL_ERROR ("vector and permutation must be the same length", GSL_EBADLEN);
}
FUNCTION (gsl_permute,inverse) (p->data, v->data, v->stride, v->size) ;
return GSL_SUCCESS;
}
int
TYPE (gsl_permute_matrix) (const gsl_permutation * p, TYPE (gsl_matrix) * A)
{
if (A->size2 != p->size)
{
GSL_ERROR ("matrix columns and permutation must be the same length", GSL_EBADLEN);
}
else
{
size_t i;
for (i = 0; i < A->size1; ++i)
{
QUALIFIED_VIEW (gsl_vector, view) r = FUNCTION (gsl_matrix, row) (A, i);
TYPE (gsl_permute_vector) (p, &r.vector);
}
return GSL_SUCCESS;
}
}
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