Monte Carlo Tests to Calculate Pi in Go

gistfile1.go

package main

import (
  "flag"
	"fmt"
	"math/rand"
	"sync"
	"time"
)

var (
	circle_area = 0.0
	square_area = 0.0
	m           sync.Mutex
	wg          sync.WaitGroup
	trials      = flag.Int("t", 10000, "number of trials to perform")
)

func one_test() {
	x := rand.Float32()
	y := rand.Float32()
	if ((x * x) + (y * y)) < 1 {
		m.Lock()
		circle_area += 1
		m.Unlock()
	}
	m.Lock()
	square_area += 1
	m.Unlock()
	wg.Done()
}

func main() {
	flag.Parse()

	t0 := time.Now()
	for i := 0; i < *trials; i++ {
		wg.Add(1)
		go one_test()
	}
	wg.Wait()
	pi := 4.0 * (circle_area / square_area)
	t1 := time.Now()
	fmt.Println("Approximate value of pi:", pi)
	fmt.Printf("Calculated %d trials in %v.\n", trials, t1.Sub(t0))
}