postgresql/src/backend/optimizer/geqo/geqo_recombination.c

/*------------------------------------------------------------------------
*
* geqo_recombination.c--
*	 misc recombination procedures
*
* $Id: geqo_recombination.c,v 1.4 1997/09/08 21:44:36 momjian Exp $
*
*-------------------------------------------------------------------------
*/

/* contributed by:
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
   *  Martin Utesch				 * Institute of Automatic Control	   *
   =							 = University of Mining and Technology =
   *  utesch@aut.tu-freiberg.de  * Freiberg, Germany				   *
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
 */

/* -- parts of this are adapted from D. Whitley's Genitor algorithm -- */

#include "postgres.h"

#include "nodes/pg_list.h"
#include "nodes/relation.h"
#include "nodes/primnodes.h"

#include "utils/palloc.h"
#include "utils/elog.h"

#include "optimizer/internal.h"
#include "optimizer/paths.h"
#include "optimizer/pathnode.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"

#include "optimizer/geqo_gene.h"
#include "optimizer/geqo.h"
#include "optimizer/geqo_recombination.h"
#include "optimizer/geqo_random.h"


/*
 * init_tour--
 *
 *	 Randomly generates a legal "traveling salesman" tour
 *	 (i.e. where each point is visited only once.)
 *	 Essentially, this routine fills an array with all possible
 *	 points on the tour and randomly chooses the 'next' city from
 *	 this array.  When a city is chosen, the array is shortened
 *	 and the procedure repeated.
 *
 */
void
init_tour(Gene *tour, int num_gene)
{
	Gene	   *tmp;
	int			remainder;
	int			next,
				i;

	tmp = (Gene *) palloc(num_gene * sizeof(Gene));

	for (i = 0; i < num_gene; i++)
	{
		tmp[i] = (Gene) i + 1;	/* builds tours "1 - 2 - 3" etc. */
	}

	remainder = num_gene - 1;

	for (i = 0; i < num_gene; i++)
	{
		next = (int) geqo_randint(remainder, 0);		/* choose city between 0
														 * and remainder */
		tour[i] = tmp[next];
		tmp[next] = tmp[remainder];
		remainder--;
	}

	pfree(tmp);
}

/* alloc_city_table--
 *
 *	 allocate memory for city table
 *
 */
City	   *
alloc_city_table(int num_gene)
{
	City	   *city_table;

	/*
	 * palloc one extra location so that nodes numbered 1..n can be
	 * indexed directly; 0 will not be used
	 */

	city_table = (City *) palloc((num_gene + 1) * sizeof(City));

	return (city_table);
}

/* free_city_table--
 *
 *	  deallocate memory of city table
 *
 */
void
free_city_table(City *city_table)
{
	pfree(city_table);
}