Get an approximation of π using probabilities of coprime integers

coprime_pi.swift

import Foundation

let rolls = 1_000_000

func getPi() -> Double {
	
	func gcd(x: Int, y: Int) -> Int {
		var internal_x = x
		var internal_y = y
		
		while internal_y != 0 {
			(internal_x, internal_y) = (internal_y, internal_x % internal_y)
		}
		return internal_x
	}
		
	var coprimesCount = 0
	for _ in 0..<rolls {
		let a = arc4random()
		let b = arc4random()
		if gcd(x: Int(a), y: Int(b)) == 1 {
			coprimesCount += 1
		}
	}
	let probability = Double(coprimesCount) / Double(rolls)
	let pi = sqrt(6.0/probability)
	print("approximatie π = \(pi)")
	print("error: \(abs(pi-M_PI) / M_PI * 100)%")
	return pi
}


for _ in 1...1000 {
	getPi()
}