monte carlo pi

a_test.go

package main

import (
	"fmt"
	"testing"

	"github.com/db47h/rand64/xoroshiro"
)

const N = 10_000_000

func BenchmarkPi(b *testing.B) {
	for n := 0; n < b.N; n++ {
		var S int64
		var rng xoroshiro.Rng128P
		rng.Seed(1111)
		for i := 0; i < N; i++ {
			x := float64(rng.Uint64()) / 18446744073709551615
			y := float64(rng.Uint64()) / 18446744073709551615
			if x*x+y*y <= 1 {
				S += 1
			}
		}
		if n == 0 {
			fmt.Println(4 * float64(S) / N)
		}
	}
}