PotcFdk/pi-goroutines.go

## pi-goroutines.go
/* pi-goroutines.go
 * This spams Goroutines to calculate pi.
 * Not a great approach, I just wanted to play around with Goroutines and channels.
 *
 * PotcFdk, 2015
 */

package main

import (
	"fmt"
	"math"
	"runtime"
	"sync"
)

func main() {
	fmt.Println(calcpi(1e8))
}

const cap int = 1e6
var free int = cap

var wg sync.WaitGroup

func calcpi(n int) float64 {
	ch := make(chan float64)

	remaining := n

	go collector( ch, n)
	wg.Add(1)

	for remaining > 0 {
		for free > 0 && remaining > 0 {
			go term (ch, float64(n - remaining))
			free--
			remaining--
		}
		runtime.Gosched()
	}

	wg.Wait()

	return <-ch
}

func collector (ch chan float64, total int) {
	sum := float64 (0.0)

	fmt.Println ("Started collector, waiting for: ", total)

	for k := 0; k < total; k++ {
		sum += <-ch
		free++
		if k % 1e6 == 0 {
			fmt.Printf ("progress: %d/%d (%d %%)\n", k, total, int(float64(k)/float64(total) * 100))
		}
	}

	fmt.Println ("Collector finished.")

	wg.Done()
	ch <- sum
}

func term (ch chan float64, k float64) {
	ch <- 4 * math.Pow(-1, k) / (2*k + 1)
}
	/* pi-goroutines.go
	* This spams Goroutines to calculate pi.
	* Not a great approach, I just wanted to play around with Goroutines and channels.
	*
	* PotcFdk, 2015
	*/

	package main

	import (
	"fmt"
	"math"
	"runtime"
	"sync"
	)

	func main() {
	fmt.Println(calcpi(1e8))
	}

	const cap int = 1e6
	var free int = cap

	var wg sync.WaitGroup

	func calcpi(n int) float64 {
	ch := make(chan float64)

	remaining := n

	go collector( ch, n)
	wg.Add(1)

	for remaining > 0 {
	for free > 0 && remaining > 0 {
	go term (ch, float64(n - remaining))
	free--
	remaining--
	}
	runtime.Gosched()
	}

	wg.Wait()

	return <-ch
	}

	func collector (ch chan float64, total int) {
	sum := float64 (0.0)

	fmt.Println ("Started collector, waiting for: ", total)

	for k := 0; k < total; k++ {
	sum += <-ch
	free++
	if k % 1e6 == 0 {
	fmt.Printf ("progress: %d/%d (%d %%)\n", k, total, int(float64(k)/float64(total) * 100))
	}
	}

	fmt.Println ("Collector finished.")

	wg.Done()
	ch <- sum
	}

	func term (ch chan float64, k float64) {
	ch <- 4 * math.Pow(-1, k) / (2*k + 1)
	}