2channels.go

package main

func main() {

}

func Merge2Channels(f func(int) int, in1 <-chan int, in2 <-chan int, out chan<- int, n int) {
	go func(f func(int) int, in1 <-chan int, in2 <-chan int, out chan<- int) {
		done := make(chan bool, n*2)
		results := make([]*int, n*2)

		go func() {
			nDone := 0
			for <-done {
				for i := nDone; i < n; i++ {
					if results[i] != nil && results[i+n] != nil {
						out <- (*results[i] + *results[i+n])
						if nDone++; nDone == n {
							return
						}
					} else {
						break
					}
				}
			}
		}()
		input := func(ch <-chan int, results []*int) {
			for i := 0; i < n; i++ {
				x := <-ch
				go func(i int, x int) {
					result := f(x)
					results[i] = &result
					done <- true
				}(i, x)
			}
		}
		go input(in1, results[:n])
		go input(in2, results[n:])

	}(f, in1, in2, out)
}

main_test.go

package main

import (
	// "fmt"
	"log"
	"math/rand"
	"testing"
	"time"
)

func TestMerge2Channels(t *testing.T) {
	f := func(n int) int {
		sleep := rand.Int31n(10000)
		// log.Println("run =", n)
		time.Sleep(time.Duration(sleep) * time.Millisecond)
		time.Sleep(2 * time.Second)
		return (n * n)
	}
	rand.Seed(12000)
	repeats := rand.Intn(400)
	in1 := make(chan int, repeats)
	in2 := make(chan int, repeats)
	out := make(chan int, repeats)
	// log.Println("Seed")
	log.Println("Merge2Channels")
	Merge2Channels(f, in1, in2, out, repeats)
	results := []int{}
	log.Println("go func")
	go func() {
		for i := 0; i < repeats; i++ {
			i1 := rand.Intn(200)
			i2 := rand.Intn(200)
			in1 <- i1
			in2 <- i2
			results = append(results, (i1*i1)+(i2*i2))
		}
	}()
	c := 0
	log.Println("range out")
	for i := range out {
		if i != results[c] {
			t.Errorf("%v != %v", i, results[c])
		}
		log.Println("out =", i)
		c++
		if c == repeats {
			close(out)
		}
	}
	log.Println("cap(in1)", cap(in1))
}