geqo_ox1.c

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/*------------------------------------------------------------------------
*
* geqo_ox1.c
*
*    order crossover [OX] routines;
*    OX1 operator according to Davis
*    (Proc Int'l Joint Conf on AI)
*
* src/backend/optimizer/geqo/geqo_ox1.c
*
*-------------------------------------------------------------------------
*/

/* contributed by:
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
   *  Martin Utesch              * Institute of Automatic Control      *
   =                             = University of Mining and Technology =
   *  [email protected]  * 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(PlannerInfo *root, 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(root, num_gene - 1, 0);
    right = geqo_randint(root, 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 */
    }

}