From cc69389d79e4bed927e9aa29b8769c2ad4f90d8c Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Sat, 25 Oct 2025 11:09:32 -0500
Subject: create simple genetic algorithm in c

---
 genalg.example.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 genalg.example.c

(limited to 'genalg.example.c')

diff --git a/genalg.example.c b/genalg.example.c
new file mode 100644
index 0000000..cfd7d4c
--- /dev/null
+++ b/genalg.example.c
@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include "genalg.h"
+
+
+struct organism_t {
+  double fitness, a, b;
+};
+
+
+double randf() {
+  return 2.0 * (((double)rand())/RAND_MAX) - 1.0;
+}
+
+
+struct organism_t * org_alloc(int randomize) {
+  struct organism_t * org = malloc(sizeof(struct organism_t));
+  if (org == NULL) {
+    fprintf(stderr, "failed to allocate organism!\n");
+    return NULL;
+  }
+
+  org->fitness = -1;
+  org->a = 0;
+  org->b = 0;
+
+  if (randomize) {
+    org->a = 20.0 * randf();
+    org->b = 20.0 * randf();
+  }
+
+  return org;
+}
+
+
+double org_fitness(void *ptr) {
+  struct organism_t *org = ptr;
+  if (org->fitness >= 0) {
+    return org->fitness;
+  } else {
+    double error = pow(org->a - 14.0, 2) + pow(org->b + 7.0, 2);
+    org->fitness = 1.0/(fabs(error)+1);
+    return org->fitness;
+  }
+}
+
+
+void * create_child(void *ptr) {
+  struct organism_t *org = ptr;
+  struct organism_t *child = org_alloc(0);
+  if (child == NULL) {
+    return NULL;
+  }
+  child->a = org->a + 0.1*randf();
+  child->b = org->b + 0.1*randf();
+  return child;
+}
+
+
+int main() {
+  genalg_t *ga = ga_create(1000, org_fitness, create_child, free);
+  for (size_t i=0; i<ga->pop_count; i++) {
+    ga->population[i] = org_alloc(1);
+  }
+  struct genalg_stats_t stats;
+  for (int i=0; i<100; i++) {
+    ga_replace_population(ga, 60, 50);
+    stats = ga_population_statistics(ga);
+    struct organism_t *org = stats.best;
+    printf(
+      "mean: %f, variance: %f\nmin: %f, max: %f\nbest: (%f, %f)\n",
+      stats.mean, stats.variance, stats.min, stats.max,
+      org->a, org->b
+    );
+  }
+  return 0;
+}
-- 
cgit v1.2.1