geqo_mutation.c

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/*------------------------------------------------------------------------
*
* geqo_mutation.c
*
*    TSP mutation routines
*
* src/backend/optimizer/geqo/geqo_mutation.c
*
*-------------------------------------------------------------------------
*/

/* contributed by:
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
   *  Martin Utesch              * Institute of Automatic Control      *
   =                             = University of Mining and Technology =
   *  [email protected]  * Freiberg, Germany                   *
   =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
 */

/* this 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_mutation.h"
#include "optimizer/geqo_random.h"

void
geqo_mutation(PlannerInfo *root, Gene *tour, int num_gene)
{
    int         swap1;
    int         swap2;
    int         num_swaps = geqo_randint(root, num_gene / 3, 0);
    Gene        temp;


    while (num_swaps > 0)
    {
        swap1 = geqo_randint(root, num_gene - 1, 0);
        swap2 = geqo_randint(root, num_gene - 1, 0);

        while (swap1 == swap2)
            swap2 = geqo_randint(root, num_gene - 1, 0);

        temp = tour[swap1];
        tour[swap1] = tour[swap2];
        tour[swap2] = temp;


        num_swaps -= 1;
    }
}