Chicken problem

chicken.go

package main

// About chickens
// https://habr.com/ru/post/348066

import (
	crand "crypto/rand"
	"fmt"
	"math"
	"math/rand"
)

const count = 400
const iteration = 1000000

const (
	_ = 1 << (8 * iota)
	p1
	p2
	p3
	p4
	p5
)

type Chicken struct {
	isPecked bool
	Left     *Chicken
	Right    *Chicken
}

type Ring [count]*Chicken

func (c *Chicken) Peck() {
	var z = rand.Intn(256)

	if z%2 == 0 {
		c.Left.isPecked = true
	} else {
		c.Right.isPecked = true
	}
}

func process(r *Ring) int {
	var ring Ring
	var cnt int

	ring = *r

	for i := range ring {
		ring[i].isPecked = false
	}

	for i := range ring {
		ring[i].Peck()
	}

	for i := range ring {
		if !ring[i].isPecked {
			cnt++
		}
	}

	return cnt
}

func initRand() {
	var seed int64

	bytes := make([]byte, 6)

	_, err := crand.Read(bytes)
	if err != nil {
		panic(err)
	}

	seed = int64(bytes[0])
	seed += int64(bytes[1]) * p1
	seed += int64(bytes[2]) * p2
	seed += int64(bytes[3]) * p3
	seed += int64(bytes[4]) * p4
	seed += int64(bytes[5]) * p5

	rand.Seed(seed)
}

func createRing() *Ring {
	var ring Ring
	var ch *Chicken

	for i := 0; i < count; i++ {
		ring[i] = new(Chicken)
	}

	for i := range ring {
		ch = ring[i]

		if i == 0 {
			ch.Left = ring[count-1]
		} else {
			ch.Left = ring[i-1]
		}

		if i == (count - 1) {
			ch.Right = ring[0]
		} else {
			ch.Right = ring[i+1]
		}
	}

	return &ring
}

func main() {
	var cnt, sum, sumsqr int
	var avg, avgsqr float64

	initRand()
	ref := createRing()
	for i := 0; i < iteration; i++ {
		cnt = process(ref)
		sum += cnt
		sumsqr += cnt * cnt
	}

	avg = float64(sum) / iteration
	avgsqr = float64(sumsqr) / iteration
	variance := math.Sqrt((avgsqr - avg*avg) / (iteration - 1))

	fmt.Printf("P: %.9f\nS: %.9f\n", avg/count, variance/count)
}