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geqo_ox1.c

/*------------------------------------------------------------------------
*
* geqo_ox1.c
*
*      order crossover [OX] routines;
*      OX1 operator according to Davis
*      (Proc Int'l Joint Conf on AI)
*
* $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_ox1.c,v 1.9 2003/11/29 22:39:49 pgsql Exp $
*
*-------------------------------------------------------------------------
*/

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

/* the ox algorithm is adopted from Genitor : */
/*************************************************************/
/*                                                                                         */
/*    Copyright (c) 1990                                                             */
/*    Darrell L. Whitley                                                             */
/*    Computer Science Department                                              */
/*    Colorado State University                                                */
/*                                                                                         */
/*    Permission is hereby granted to copy all or any part of  */
/*    this program for free distribution.   The author's name  */
/*    and this copyright notice must be included in any copy.  */
/*                                                                                         */
/*************************************************************/

#include "postgres.h"
#include "optimizer/geqo_random.h"
#include "optimizer/geqo_recombination.h"


/* ox1
 *
 *     position crossover
 */
void
ox1(Gene *tour1, Gene *tour2, Gene *offspring, int num_gene, City *city_table)
{
      int               left,
                        right,
                        k,
                        p,
                        temp;

      /* initialize city table */
      for (k = 1; k <= num_gene; k++)
            city_table[k].used = 0;

      /* select portion to copy from tour1 */
      left = geqo_randint(num_gene - 1, 0);
      right = geqo_randint(num_gene - 1, 0);

      if (left > right)
      {
            temp = left;
            left = right;
            right = temp;
      }

      /* copy portion from tour1 to offspring */
      for (k = left; k <= right; k++)
      {
            offspring[k] = tour1[k];
            city_table[(int) tour1[k]].used = 1;
      }

      k = (right + 1) % num_gene; /* index into offspring */
      p = k;                                    /* index into tour2 */

      /* copy stuff from tour2 to offspring */
      while (k != left)
      {
            if (!city_table[(int) tour2[p]].used)
            {
                  offspring[k] = tour2[p];
                  k = (k + 1) % num_gene;
                  city_table[(int) tour2[p]].used = 1;
            }
            p = (p + 1) % num_gene; /* increment tour2-index */
      }

}

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