evolve.js

/*
 * The evolver will be used to combine all genetic operators
 * and loop to evolve the wanted program
 *
 * mutate => {Function} used to mutate a selection of programs
 * generate => {Function} used to create random programs and fill the new population until it has its initial size
 * crossover => {Function} used to mate random programs of a selection
 * population => {Array<Program>} initial random population
 * stopWhen => {Function} used to decide when to stop the evolve loop
 * onIteration => {Function} called on each evolve iteration
 * select => {Function} used to select the best individuals for the next generation
 */

const random = array => () => {
  return array[Math.floor(Math.random() * array.length)];
};

export const createEvolver = ({
  mutate,
  generate,
  crossover,
  population,
  stopWhen,
  onIteration,
  select
}) => () => {
  let counter = 0;

  while (++counter) {
    const [selection, bestFitness, bestProgram] = select(population);

    const newPopulation = [
      bestProgram,
      ...selection,
      // ...mutate(population),
      ...mutate(selection),
      ...crossover(selection)
      // ...crossover(population),
    ];

    while (newPopulation.length < population.length) {
      const result = generate();
      // const result = random(population)();
      newPopulation.push(result);
    }

    population = newPopulation;

    onIteration(counter, bestFitness, bestProgram);

    if (stopWhen(counter, bestFitness)) {
      return [bestProgram, bestFitness];
    }
  }
};