adjust chooseSurvivors -> chooseByFertility to also give the champions

src/site/snake/brain-neat.ts

@@ -348,12 +348,12 @@ export function initialSpeciate(
     return population;
 }
 
-interface SurvivorsConfig {
-    survival_threshold: number;
+interface FertilityConfig {
+    fertile_threshold: number;
     champion_min_species_size: number;
 }
-export function chooseSurvivors(population: Population, fitness: Map<Genome, number>, config: SurvivorsConfig) {
-    const { survival_threshold, champion_min_species_size } = config;
+export function chooseByFertility(population: Population, fitness: Map<Genome, number>, config: FertilityConfig) {
+    const { fertile_threshold, champion_min_species_size } = config;
 
     const species = mapInvert(population);
 
@@ -364,22 +364,22 @@ export function chooseSurvivors(population: Population, fitness: Map<Genome, num
         return [k, v / speciesSize];
     });
 
-    const survivors = new Set<Genome>();
+    const fertile = new Set<Genome>();
 
     // add sufficiently fit organisms
     const genomes: Genome[] = Array.from(population.keys());
-    const survival_idx = Math.floor(genomes.length * survival_threshold);
+    const survival_idx = Math.floor(genomes.length * fertile_threshold);
     genomes.sort((a, b) => adjFitness.get(a)! - adjFitness.get(b)!);
-    genomes.slice(survival_idx).forEach(o => survivors.add(o));
+    genomes.slice(survival_idx).forEach(o => fertile.add(o));
 
     // add species champions
     const champions = mapMap(species, (k, v) => [k, keyMax(v, o => adjFitness.get(o)!)]);
     for (const [sid, c] of champions.entries()) {
         if (species.get(sid)!.size < champion_min_species_size) continue;
-        survivors.add(c);
+        fertile.add(c);
     }
 
-    return survivors;
+    return { fertile, champions };
 }
 
 interface MateChoiceConfig {
@@ -594,6 +594,26 @@ export function mutate(genome: Genome, config: MutateConfig): Genome {
     return newGenome;
 }
 
+interface NextGenerationConfig {
+    fc: FertilityConfig;
+}
+export function computeNextGeneration(
+    population: Population,
+    fitness: Map<Genome, number>,
+    config: NextGenerationConfig,
+) {
+    const { fc } = config;
+
+    const { fertile, champions } = chooseByFertility(population, fitness, fc);
+
+    // TODO: only copy over champions, the rest mate to produce the population
+    const nextGeneration = new Map(Array.from(fertile).map(s => [s, population.get(s)!]));
+    const species = mapInvert(nextGeneration);
+    const reps = mapMap(species, (sid, genomes) => [sid, genomes.values().next().value]);
+
+    // TODO: update chooseSurvivors so champions get copied over
+}
+
 export function activate(n: number) {
     // modified sigmoid function from NEAT paper
     return 1 / (1 + Math.exp(-4.9 * n));

src/test/test-brain-neat.ts

@@ -2,7 +2,7 @@ import {
     activate,
     alignGenomes,
     chooseMate,
-    chooseSurvivors,
+    chooseByFertility,
     compatibilityDistance,
     crossGenomes,
     findAcyclicNewConns,
@@ -192,11 +192,11 @@ function testChooseSurvivors() {
 
     // (1 - 4/6) = 2/6 survive by fitness alone
     // top genome (champion) from all species with at least 3 genomes should always survive
-    const sc = { survival_threshold: 4 / 6, champion_min_species_size: 3 };
-    const survivors = chooseSurvivors(population, fitness, sc);
+    const sc = { fertile_threshold: 4 / 6, champion_min_species_size: 3 };
+    const { fertile, champions } = chooseByFertility(population, fitness, sc);
 
     assertSetEqual(
-        survivors,
+        fertile,
         new Set([
             genomeB, // champion of species 1
             genomeD, // #2 fitness
@@ -204,6 +204,10 @@ function testChooseSurvivors() {
             // genomeF not included since species is not large enough to have a champion
         ]),
     );
+    assert(champions.size === 3);
+    assert(champions.get(1)! === genomeB);
+    assert(champions.get(2)! === genomeE);
+    assert(champions.get(3)! === genomeF);
 }
 addTest(testChooseSurvivors);