gistfile1.go

package main

import (
	"rand"
	"time"
	"flag"
	"fmt"
)

func getCoord(rg *rand.Rand) float64 {
	return -1 + rg.Float64()
}

func countInsidePoints(result chan<- int, iter int) {
	inside := 0
	rg := rand.New(rand.NewSource(time.Nanoseconds()))

	for i := 0; i < iter; i++ {
		x, y := getCoord(rg), getCoord(rg)

		if (x*x + y*y) < 1.0 {
			inside++
		}
	}

	result <- inside
}

func CalcPI(iter, processes int) float64 {
	inside := 0

	result := make(chan int, processes)

	for i := 0; i < processes; i++ {
		go countInsidePoints(result, iter)
	}

	for i := 0; i < processes; i++ {
		inside += <-result
	}

	return 4 * float64(inside) / float64(iter * processes)
}

func main() {
	iter := flag.Int("iter", 1000000, "Iterations per process")
	processes := flag.Int("processes", 4, "Num of processes")

	flag.Parse()

	start := time.Nanoseconds()
	fmt.Printf("Approx PI value %f calculated in %f ms\n", 
		CalcPI(*iter, *processes),
		float(time.Nanoseconds() - start) / float(10e6))
}