82 lines
1.5 KiB
Go
82 lines
1.5 KiB
Go
// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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// For more tutorials : https://learngoprogramming.com
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// In-person training : https://www.linkedin.com/in/inancgumus/
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// Follow me on twitter: https://twitter.com/inancgumus
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package main
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import (
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"fmt"
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"math"
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"math/rand"
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"os"
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"runtime"
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"strconv"
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"time"
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)
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func main() {
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if len(os.Args) != 2 {
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exit("Please provide the sample rate")
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}
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samples, err := strconv.Atoi(os.Args[1])
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if err != nil {
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exit("Incorrect sample rate")
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}
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elapse := measure(time.Now())
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pi := spread(samples, runtime.NumCPU())
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fmt.Println("PI : ", pi)
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fmt.Println("Time: ", elapse())
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}
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func exit(msg string) {
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fmt.Fprintln(os.Stderr, msg)
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os.Exit(1)
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}
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func measure(start time.Time) func() time.Duration {
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return func() time.Duration {
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return time.Since(start)
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}
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}
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// spread the work to P number of estimate go funcs.
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// returns the estimation.
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func spread(samples int, P int) (estimated float64) {
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counts := make(chan float64)
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for i := 0; i < P; i++ {
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go func() { counts <- estimate(samples / P) }()
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}
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for i := 0; i < P; i++ {
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estimated += <-counts
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}
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return estimated / float64(P)
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}
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func estimate(N int) float64 {
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const radius = 1.0
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var (
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seed = rand.NewSource(time.Now().UnixNano())
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random = rand.New(seed)
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inside int
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)
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for i := 0; i < N; i++ {
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x, y := random.Float64(), random.Float64()
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if num := math.Sqrt(x*x + y*y); num < radius {
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inside++
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}
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}
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return 4 * float64(inside) / float64(N)
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}
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