ga

Documentation

Overview

Package ga implements the genetic algorithm.

Index

• type Entity
• type GA
  • func New(n int, gen func() Entity) *GA
  • func (a *GA) Elite() Entity
  • func (a *GA) Evolve(n int, max int) (Entity, float64, bool)
  • func (a *GA) Fitness() float64
  • func (a *GA) Next() (Entity, float64)

Examples

• GA

Types

type Entity

type Entity interface {
	// Fitness represents the fitness of this entity.
	Fitness() float64
	// Mutate is the mutation operation.
	Mutate() Entity
	// Cross is the crossover operation.
	Cross(float64, Entity) Entity
}

Entity represents an entity of GA model.

type GA

type GA struct {
	// contains filtered or unexported fields
}

GA represents the GA model.

Example

package main

import (
	"fmt"
	"math/rand"

	"gitee.com/ofunc/ga"
)

// V is an entity of GA model.
type V struct {
	X, Y float64
}

// Fitness is the fitness of this entity.
// The problem to be solved is:
//
//	max = 2x + 3y
//	4x + 3y <= 10
//	3x + 5y <= 12
//	x, y >= 0
func (v V) Fitness() float64 {
	s, f := 0.0, 2*v.X+3*v.Y
	if d := (4*v.X+3*v.Y)/10 - 1; d > 0 {
		s += d
	}
	if d := (3*v.X+5*v.Y)/12 - 1; d > 0 {
		s += d
	}
	if s > 0 {
		return -s
	} else {
		return f
	}
}

// Mutate is the mutation operation.
func (v V) Mutate() ga.Entity {
	return V{10 * rand.Float64(), 10 * rand.Float64()}
}

// Crossover is the crossover operation.
func (v V) Cross(w float64, e ga.Entity) ga.Entity {
	a := e.(V)
	return V{w*v.X + (1-w)*a.X, w*v.Y + (1-w)*a.Y}
}

func main() {
	m := ga.New(1000, V{}.Mutate)
	e, f, ok := m.Evolve(30, 10000)
	fmt.Println("fitness: ", f)
	fmt.Println("elite:", e)
	fmt.Println("isok:", ok)
}

func New

func New(n int, gen func() Entity) *GA

New creates a GA model.

func (*GA) Elite

func (a *GA) Elite() Entity

Elite returns the current elite.

func (*GA) Evolve

func (a *GA) Evolve(n int, max int) (Entity, float64, bool)

Evolve runs the GA model until the elite n generations have not changed, or the max of iterations has been reached.

func (*GA) Fitness

func (a *GA) Fitness() float64

Fitness returns the fitness of current elite.

func (*GA) Next

func (a *GA) Next() (Entity, float64)

Next gets the next generation of GA model, and returns the current elite and fitness.