126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
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/* lil-gp Genetic Programming System, version 1.0, 11 July 1995
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* Copyright (C) 1995 Michigan State University
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* Douglas Zongker (zongker@isl.cps.msu.edu)
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* Dr. Bill Punch (punch@isl.cps.msu.edu)
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*
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* Computer Science Department
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* A-714 Wells Hall
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* Michigan State University
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* East Lansing, Michigan 48824
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* USA
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*
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*/
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#include <lilgp.h>
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typedef struct
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{
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int count;
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} tournament_data;
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/* select_tournament_context()
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*
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* returns a selection context for the tournament selection method.
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*/
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sel_context *select_tournament_context ( int op, sel_context *sc,
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population *p, char *string )
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{
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char **argv;
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int i, j;
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tournament_data *td;
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switch ( op )
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{
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case SELECT_INIT:
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sc = (sel_context *)MALLOC ( sizeof ( sel_context ) );
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/* fill in fields of the selection context. */
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sc->p = p;
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sc->select_method = select_tournament;
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sc->context_method = select_tournament_context;
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/* store the tournament data record. */
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td = (tournament_data *)MALLOC ( sizeof ( tournament_data ) );
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/* parse the options. */
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td->count = 2;
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j = parse_o_rama ( string, &argv );
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for ( i = 1; i < j; ++i )
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{
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/* "size" is the only valid option. */
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if ( strcmp ( argv[i], "size" ) == 0 )
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td->count = atoi ( argv[++i] );
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else
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error ( E_FATAL_ERROR, "unknown tournament option \"%s\".",
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argv[i] );
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}
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free_o_rama ( j, &argv );
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if ( td->count <= 0 )
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error ( E_FATAL_ERROR,
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"tournament size must be at least 1. (%s)", string );
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sc->data = (void *)td;
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return sc;
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break;
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case SELECT_CLEAN:
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td = (tournament_data *)(sc->data);
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FREE ( sc->data );
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FREE ( sc );
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return NULL;
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break;
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}
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return NULL;
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}
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/* select_tournament()
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*
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* does a tournament selection. randomly picks (uniformly) a number (size)
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* of individuals, then selects the best one among those.
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*/
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int select_tournament ( sel_context *sc )
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{
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int i, j, k;
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tournament_data *td;
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population *p;
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td = (tournament_data *)(sc->data);
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p = sc->p;
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j = -1;
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for ( i = 0; i < td->count; ++i )
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{
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/* pick another individual. */
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k = random_int ( &globrand, p->size );
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/* save it if it is better than the current best. */
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if ( j == -1 || p->ind[k].a_fitness > p->ind[j].a_fitness )
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j = k;
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}
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return j;
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}
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