gistfile1.txt

package main

import (
  "fmt"
)

const NCPU = 16

func main() {
	sum := Concurrent(1000)
	fmt.Printf("Sum: %i", sum)
}

func Serial(max int64) int64 {
	sum := int64(0)
	for i := int64(1); i < max; i++ {
		if i%3 == 0 || i%5 == 0 {
			sum += i
		}
	}
	return sum
}

func Concurrent(max int64) int64 {
	c := make(chan int64, NCPU)
	//Send discrete ranges to each goroutine to get calculated independantly. 
	for i := int64(0); i < NCPU; i++ {
		go CalculateSum(i*max/NCPU, (i+1)*max/NCPU, c)
	}

	var sum int64
	sum = 0

	for i := int64(0); i < NCPU; i++ {
		sum += <-c
	}
	return sum
}

func CalculateSum(min, max int64, c chan int64) {
	sum := int64(0)
	for i := min; i < max; i++ {
		if i%3 == 0 || i%5 == 0 {
			sum += i
		}
	}
	c <- sum
}