Genetic.ts

A simple yet powerful and hackable Genetic Algorithm library. Handles your parent finding, crossover and mutation. Contains also some helpful functions to get you quickly started.

• Genetic.ts
  • installation
  • usage
  • configuration
  • population
  • modes
    • Parent selection modes:
    • Crossover modes:
  • mutating
  • history
  • premade mutation functions
    • chance
    • add

installation

As a module:

npm i genetic.ts
# or
yarn add genetic.ts

For browser:

<script src="https://cdn.jsdelivr.net/npm/genetic.ts/dist/genetic.web.js"></script>

usage

See examples. Source code can be found in docs/.

import * as genetic from 'genetic.ts' /* import the library, this object will be available globally if imported through HTML */

const population = [
  {
    dna: [1, 2, 4],
    fitness() {
      return this.dna.reduce((a, b) => a + b)
    }
  },
  {
    dna: [4, 4, 8],
    fitness() {
      return this.dna.reduce((a, b) => a + b)
    }
  },
  {
    dna: [11, 3, 7],
    fitness() {
      return this.dna.reduce((a, b) => a + b)
    }
  }
]

/* create your genetic object */
const ga = new genetic.Instance({
  population /* set your population */,
  mutationFunction: genetic.chance(
    genetic.add(-0.5, 0.5)
  ) /* add mutation function */,
  modes: {
    crossover:
      genetic.CrossoverModes.clone /* overwrite default modes with enums */
  }
})

/* All Genetic's methods are chainable */
ga.findParents() /* finds parents using the passed mode */
  .crossover() /* creates new genes using the passed mode */
  .mutate() /* mutates the genes using the passed function */
  .finishGeneration() /* Overwrites your population's dna and increments the generation counter */

/* or use the `nextGeneration` method to do the above all at once */
ga.nextGeneration()

configuration

The genetic.Instance class accepts a configuration object in the constructor. Genetic instance will follow the same structure. Here's the object it accepts with its defaults (those that do not have a default require a value to be passed):

• population: array containing your members that satisfy the IPopMember interface
• mutationFunction: function to be used when mutating the genes
• mutationRate: mutation rate of the algorithm (default: 0.1)
• amountOfParents: amount of parents to be chosen from the mating pool (default: 2)
• modes: object containing properties specifying the modes:
  • parentsSelection: method of choosing the parents (default: 'best')
  • crossover: method of crossing parents' genes (default: 'random')
• preserveParents: preservation of parents' dna in the new generation. If you set this to true and have modes.parentsSelection = 'best' you will ensure the next generations wont get worse (default: false)
• keepHistory: saves history of parents of every generation in this.history

population

A population is considered correct when:

interface IPopMember<DNA> {
  fitness(): number
  dna: DNA
}

• it is an array
• each element in the array is an object implementing IPopMember:
  • contains a fitness method that returns the fitness (number)
  • contains a dna property:
    • can be any data structure as long as it ends with a number
    • the structure is the same for every member in the array

If you're unsure whether your population is correct you can always use genetic.validatePopulation(pop) that will throw an error if something is wrong.

modes

Parent selection modes:

methods of choosing the parents

best: takes members with highest fitness scores

probability: selects members based on their fitness scores that will correspond to the chance of being chosen

probability2: selects members based on their fitness scores squared that will correspond to the chance of being chosen

probability3: selects members based on their fitness scores cubed that will correspond to the chance of being chosen

Crossover modes:

method of crossing parents' genes

random: randomly choosing a parent for each gene

average: averaging all parents' dna

clone: randomly selecting a parent and cloning his dna

mutating

A mutation function accepts data about the current gene and will return a number that will be added to the gene.

A mutation function is considered correct when:

type MutationFunction = (mutationRate: number) => number

• will accept a mutationRate
• will return a number

history

If enabled history is stored under ga.history. It is saved each time ga.findParents() is called. It is an array of arrays of all previous parents with their fitness and dna:

type HistoryRecord<DNA> = {
  fitness: number
  dna: DNA
}[]

premade mutation functions

Genetic.ts provides some pre-made functions for mutations:

chance

If you'd like to mutate only some properties (based on the mutation rate) wrap your function in chance(yourFunction), like so:

const mutFunc = chance(mRate => 2 * mRate)

add

If you'd like to mutate values by some random number in a range use add(min, max):

const mutFunc = add(-0.3, 0.3) /* min inclusive, max exclusive */