| /* permutation/permute_source.c |
| * |
| * Copyright (C) 1996, 1997, 1998, 1999, 2000 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 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. |
| */ |
| |
| /* 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; |
| } |