Leibniz in Go

multithread.go

package main

import (
	"fmt"
	"math"
)

func main() {
	const MAX = 4
	const N = 100000000
	UNIT := int(N/MAX)
	ch := make(chan float64, MAX)
	for i := 0; i< MAX; i++ {
		go func(begin int, end int) {
			s := 0.0
			for begin < end {
				s += math.Pow(-1.0, float64(begin))/ float64(2 * begin + 1)
				begin++
			}
			ch <- s
		}(UNIT*i, UNIT*(i+1))
	}
	var s float64
	for i := 0; i < MAX; i++ {
		s += <- ch
	}
	fmt.Println(4 * s)
}

singlethread.go

package main

import (
	"fmt"
	"math"
)

func main(){
	n := 0
	s := 0.0
	nmax := int(math.Pow(10,8))
	for n < nmax {
		s += math.Pow(-1.0, float64(n))/ float64(2 * n + 1)
		n += 1
	}
	fmt.Println(4 * s)
}