MaxHalford/eaopt

package eaopt

import (
    "log"
    "math/rand"
    "time"

    "golang.org/x/sync/errgroup"
)

// A Population contains individuals. Individuals mate within a population.
// Individuals can migrate from one population to another. Each population has a
// random number generator to bypass the global rand mutex.
type Population struct {
    Individuals Individuals   `json:"indis"`
    Age         time.Duration `json:"age"`
    Generations uint          `json:"generations"`
    ID          string        `json:"id"`
    RNG         *rand.Rand
}

// Generate a new population.
func newPopulation(size uint, parallel bool, newGenome func(rng *rand.Rand) Genome, rng *rand.Rand) Population {
    var (
        popRNG = rand.New(rand.NewSource(rng.Int63()))
        pop    = Population{
            Individuals: newIndividuals(size, parallel, newGenome, popRNG),
            ID:          randString(3, popRNG),
            RNG:         popRNG,
        }
    )
    return pop
}

// Log a Population's current statistics with a provided log.Logger.
func (pop Population) Log(logger *log.Logger) {
    logger.Printf(
        "pop_id=%s min=%f max=%f avg=%f std=%f",
        pop.ID,
        pop.Individuals.FitMin(),
        pop.Individuals.FitMax(),
        pop.Individuals.FitAvg(),
        pop.Individuals.FitStd(),
    )
}

// Populations type is necessary for migration and speciation purposes.
type Populations []Population

// Apply a function to a slice of Populations.
func (pops Populations) Apply(f func(pop *Population) error) error {
    var g errgroup.Group
    for i := range pops {
        i := i // https://golang.org/doc/faq#closures_and_goroutines
        g.Go(func() error {
            return f(&pops[i])
        })
    }
    return g.Wait()
}