/*------------------------------------------------------------------------- * * geqo_selection.c *	  linear selection scheme for the genetic query optimizer * * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * $Id: geqo_selection.c,v 1.15 2003/08/04 02:39:59 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 "postgres.h"#include <math.h>#include "optimizer/geqo_copy.h"#include "optimizer/geqo_random.h"#include "optimizer/geqo_selection.h"static int	linear(int max, double bias);/* geqo_selection * *	 according to bias described by input parameters, *	 second genes are selected from the pool */voidgeqo_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 intlinear(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;}