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// example demonstrating performance of GA search algorithm for finding basic function peak
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "liquid.h"
#define OUTPUT_FILENAME "gasearch_example.m"
// peak callback function; value nearest {p, p, p, ...} where p = 1/sqrt(2)
float peak_callback(void * _userdata, chromosome _c)
{
unsigned int i, n = chromosome_get_num_traits(_c);
float u_global = 1.0f;
float sig = 0.2f;
float p = M_SQRT1_2;
for (i=0; i<n; i++) {
// extract chromosome values
float v = chromosome_valuef(_c,i);
float e = v - p;
float u = exp(-e*e/(2*sig*sig));
u_global *= u;
}
return u_global;
}
int main() {
unsigned int num_parameters = 16; // dimensionality of search (minimum 1)
unsigned int bits_per_parameter = 6; // parameter resolution
unsigned int num_iterations = 8000; // number of iterations to run
unsigned int population_size = 32; // GA population size
float mutation_rate = 0.2f; // GA mutation rate
unsigned int i;
float optimum_utility;
// create prototype chromosome
chromosome prototype = chromosome_create_basic(num_parameters, bits_per_parameter);
// create gasearch object
gasearch ga = gasearch_create_advanced(peak_callback, NULL, prototype,
LIQUID_OPTIM_MAXIMIZE, population_size, mutation_rate);
gasearch_print(ga);
// execute search at once
//optimum_utility = gasearch_run(ga, num_iterations, -1e-6f);
// open output file for exporting results
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
// execute search one iteration at a time
fprintf(fid,"u = zeros(1,%u);\n", num_iterations);
for (i=0; i<num_iterations; i++) {
// step
gasearch_evolve(ga);
// get optimum utility and print results
gasearch_getopt(ga, prototype, &optimum_utility);
fprintf(fid,"u(%3u) = %12.4e;\n", i+1, optimum_utility);
printf("%4u : %16.8f\n", i, optimum_utility);
}
// print results
printf("\n");
gasearch_print(ga);
printf("optimum utility : %12.8f\n", optimum_utility);
chromosome_printf(prototype);
fprintf(fid,"figure;\n");
fprintf(fid,"plot(u);\n");
fprintf(fid,"xlabel('iteration');\n");
fprintf(fid,"ylabel('utility');\n");
fprintf(fid,"title('gradient search results');\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
chromosome_destroy(prototype);
gasearch_destroy(ga);
return 0;
}
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