/*------------------------------------------------------------------------
*
* geqo_px.c--
*
*    position crossover [PX] routines;
*    PX operator according to Syswerda
*    (The Genetic Algorithms Handbook, L Davis, ed)
*
* $Id: geqo_px.c,v 1.1 1997/02/19 12:57:37 scrappy Exp $
*
*-------------------------------------------------------------------------
*/

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

/* the px 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"


/* px--
 *
 *   position crossover
 */
void
px(Gene *tour1, Gene *tour2, Gene *offspring, int num_gene, City *city_table)
{

    int num_positions;
    int i, pos, tour2_index, offspring_index;

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

    /* choose random positions that will be inherited directly from parent */
    num_positions = geqo_randint (2*num_gene/3, num_gene/3);	

    /* choose random position */
    for (i=0; i<num_positions; i++) {	
       pos = geqo_randint (num_gene - 1, 0);

       offspring[pos] = tour1[pos]; /* transfer cities to child */
       city_table[(int) tour1[pos]].used = 1; /* mark city used */
    }

    tour2_index = 0;
    offspring_index = 0;


    /* px main part */

    while (offspring_index < num_gene) {

	/* next position in offspring filled */
       if (!city_table[(int) tour1[offspring_index]].used) {

	/* next city in tour1 not used */
       	if (!city_table[(int) tour2[tour2_index]].used) {

		/* inherit from tour1 */
		     offspring[offspring_index] = tour2[tour2_index];

		     tour2_index++;
		     offspring_index++;
		  }
       	else { /* next city in tour2 has been used */
		     tour2_index++;
 		  }

       	}
       else { /* next position in offspring is filled */
	  offspring_index++;
       }

    }

 }