geqo_recombination.c File Reference

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

Include dependency graph for geqo_recombination.c:

Go to the source code of this file.

Functions
void	init_tour (PlannerInfo *root, Gene *tour, int num_gene)

Function Documentation

init_tour()

void init_tour	(	PlannerInfo *	root,
		Gene *	tour,
		int	num_gene
	)

Definition at line 34 of file geqo_recombination.c.

{
    int         i,
                j;
 
    /*
     * We must fill the tour[] array with a random permutation of the numbers
     * 1 .. num_gene.  We can do that in one pass using the "inside-out"
     * variant of the Fisher-Yates shuffle algorithm.  Notionally, we append
     * each new value to the array and then swap it with a randomly-chosen
     * array element (possibly including itself, else we fail to generate
     * permutations with the last city last).  The swap step can be optimized
     * by combining it with the insertion.
     */
    if (num_gene > 0)
        tour[0] = (Gene) 1;
 
    for (i = 1; i < num_gene; i++)
    {
        j = geqo_randint(root, i, 0);
        /* i != j check avoids fetching uninitialized array element */
        if (i != j)
            tour[i] = tour[j];
        tour[j] = (Gene) (i + 1);
    }
}

References geqo_randint(), i, j, and root.

Referenced by random_init_pool().