/*------------------------------------------------------------------------
*
* geqo_cx.c--
*
*    cycle crossover [CX] routines;
*    CX operator according to Oliver et al
*    (Proc 2nd Int'l Conf on GA's)
*
* $Id: geqo_cx.c,v 1.1 1997/02/19 12:56:48 scrappy Exp $
*
*-------------------------------------------------------------------------
*/

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

/* the cx 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 "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"


/* cx--
 *
 *   cycle crossover
 */
int
cx(Gene *tour1, Gene *tour2, Gene *offspring, int num_gene, City *city_table)
{

    int i, start_pos, curr_pos;
    int count = 0;
    int num_diffs = 0;

    /* initialize city table */
    for (i=1; i<=num_gene; i++)	{
       city_table[i].used = 0;
       city_table[tour2[i-1]].tour2_position = i-1;
       city_table[tour1[i-1]].tour1_position = i-1;
    }

    /* choose random cycle starting position */
    start_pos = geqo_randint(num_gene - 1, 0);

    /* child inherits first city  */
    offspring[start_pos] = tour1[start_pos];

    /* begin cycle with tour1 */
    curr_pos = start_pos;
    city_table[(int) tour1[start_pos]].used = 1;

    count++;

    /* cx main part */


/* STEP 1 */

    while (tour2[curr_pos] != tour1[start_pos])  {
       city_table[(int) tour2[curr_pos]].used = 1;
       curr_pos = city_table[(int) tour2[curr_pos]].tour1_position;
       offspring[curr_pos] = tour1[curr_pos];
       count++;
    	}


/* STEP 2 */

    /* failed to create a complete tour */
    if (count < num_gene)  {
       for (i=1; i<=num_gene; i++) {
	  if (!city_table[i].used) {
	     offspring[city_table[i].tour2_position] =
			tour2[(int) city_table[i].tour2_position];
	     count++;
	  	}
       	}
    }


/* STEP 3 */

    /* still failed to create a complete tour */
    if (count < num_gene) {

    /* count the number of differences between mom and offspring */ 
    	for (i=0; i<num_gene; i++)
      	 if (tour1[i] != offspring[i]) num_diffs++;	

       }

 return(num_diffs);
 }

