A golang implementation of the napa-js estimate pi example

estimate_pi.go

package main

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

func estimatePi(points float64) float64 {
	var i = points
	var inside float64
	r := rand.New(rand.NewSource(time.Now().UnixNano()))

	var x, y float64
	for ; i > 0; i-- {
		x = r.Float64()
		y = r.Float64()
		if (x*x)+(y*y) <= 1 {
			inside++
		}
	}
	return inside / points * 4
}

func run(points, batches int) (result float64, elapsed time.Duration) {
	start := time.Now()
	batchSize := float64(points) / float64(batches)

	results := make([]float64, batches)
	wg := sync.WaitGroup{}
	wg.Add(batches)

	for i := 0; i < batches; i++ {
		go func(index int) {
			defer wg.Done()
			results[index] = estimatePi(batchSize)
		}(i)
	}
	wg.Wait()

	for _, subResult := range results {
		result += subResult
	}
	result = result / float64(batches)
	elapsed = time.Since(start)
	printResults(points, batches, result, elapsed)
	return
}

func printResults(points, batches int, pi float64, elapsed time.Duration) {
	fmt.Printf("\t%d\t\t%d\t\t%s\t\t%v\t\t%.7f\t\t%.7f\n", points, batches, os.Getenv("GOMAXPROCS"), elapsed, pi, math.Abs(pi-math.Pi))
}

func main() {
	fmt.Printf("\t# of points\t# of batches\t# of workers\tlatency in MS\testimated π\tdeviation\n")
	fmt.Printf("\t---------------------------------------------------------------------------------------\n")
	run(4000000, 1)
	run(4000000, 2)
	run(4000000, 4)
	run(4000000, 8)
}