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/*-------------------------------------------------------------------------
*
* geqo_selection.c--
* linear selection scheme for the genetic query optimizer
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: geqo_selection.c,v 1.4 1997/09/08 21:44:41 momjian Exp $
*
*-------------------------------------------------------------------------
*/
/* contributed by:
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
* Martin Utesch * Institute of Automatic Control *
= = University of Mining and Technology =
* utesch@aut.tu-freiberg.de * Freiberg, Germany *
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
*/
/* this is adopted from D. Whitley's Genitor algorithm */
/*************************************************************/
/* */
/* 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 <math.h>
#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_selection.h"
#include "optimizer/geqo_copy.h"
#include "optimizer/geqo_random.h"
static int linear(int max, double bias);
/* geqo_selection--
*
* according to bias described by input parameters,
* second genes are selected from the pool
*/
void
geqo_selection(Chromosome *momma, Chromosome *daddy, Pool *pool, double bias)
{
int first,
second;
first = (int) linear(pool->size, bias);
second = (int) linear(pool->size, bias);
if (pool->size > 1)
{
while (first == second)
second = (int) linear(pool->size, bias);
}
geqo_copy(momma, &pool->data[first], pool->string_length);
geqo_copy(daddy, &pool->data[second], pool->string_length);
}
/* linear--
* generates random integer between 0 and input max number
* using input linear bias
*
* probability distribution function is: f(x) = bias - 2(bias - 1)x
* bias = (prob of first rule) / (prob of middle rule)
*
*/
static int
linear(int pool_size, double bias) /* bias is y-intercept of linear
* distribution */
{
double index; /* index between 0 and pop_size */
double max = (double) pool_size;
index =
max * (bias - sqrt((bias * bias) - 4.0 * (bias - 1.0) * geqo_rand()))
/ 2.0 / (bias - 1.0);
return ((int) index);
}
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