#ifndef lint
static char *rcsid = "$Header: /tmp_mnt/vida/disks/disk5/Users/terry/r/gassy/RCS/selectors.c,v 1.3 1992/10/09 06:43:50 terry Exp terry $";
#endif


#include "types.h"

VOID *
roulette_selection(reproducers, nselections, context)
INT *reproducers;
INT *nselections;
CONTEXT* context;
{
    register INT i;
    FITNESS total_fitness = context->total_fitness;
    register INT population_size = context->population_size;

    /* 
     * If everyone is totally unfit, choose them at random.
     */
    if (total_fitness == (FITNESS)0){
	for (i = 0; i < population_size; i++){
	    reproducers[i] = uniform(context->population_size);
	} 
	
	*nselections = population_size;
	return 0;
    }

    /* 
     * Select the machines that will reproduce. 
     */
    for (i = 0; i < population_size; i++){
	
	register FITNESS where = (FITNESS) (uniform((INT) total_fitness) + (FITNESS) 1);   /* produces 1..total_fitness */
	register INT reproducer = 0;
	
	while (where > (FITNESS) 0){
	    where -= context->population[reproducer].fitness;
	    reproducer++;
	}
	
	reproducers[i] = reproducer - 1;
    } 
    
    *nselections = population_size;
    return 0;
}

#define TOURNAMENT_SELECTION_WITH_REPLACEMENT

VOID *
tournament_selection(reproducers, nselections, context)
INT *reproducers;
INT *nselections;
CONTEXT* context;
{
    register INT i;
    register INT population_size = context->population_size;

    /* Select the strings that will survive via a tournament. */
    for (i = 0; i < population_size; i++){
	register INT a = uniform(population_size);
	register INT b;
	
#if defined(TOURNAMENT_SELECTION_WITH_REPLACEMENT)
	b = uniform(population_size);
	
	if (a == b){
	    reproducers[i] = a;
	    continue;
	}
#else
	do {
	    b = uniform(population_size);
	} while (a == b);
#endif

	if (DO_TOURNAMENT){
	    /* Choose the most fit of the two. */
	    if (context->population[a].fitness > context->population[b].fitness){
		reproducers[i] = a;
	    }
	    else {
		reproducers[i] = b;
	    }
	}
	else {
	    /* Choose the less fit of the two. */
	    if (context->population[a].fitness > context->population[b].fitness){
		reproducers[i] = b;
	    }
	    else {
		reproducers[i] = a;
	    }
	}
    }
    
    *nselections = population_size;
    return 0;
}


VOID *
select_all(reproducers, nselections, context)
INT *reproducers;
INT *nselections;
CONTEXT* context;
{
    register INT i;
    register INT population_size = context->population_size;

    for (i = 0; i < population_size; i++){
	reproducers[i] = i;
    }
    
    *nselections = population_size;
    return 0;
}