func producer(out chan<- int, v int) { for i := 0; i < 10; i++ { out <- v time.Sleep(time.Duration(v) * time.Second) } } func consumer() { ch := make(chan int) go producer(ch, 1) go producer(ch, 2) // producerが送信した値を集約して出力 for i := range ch { fmt.Println(i) } }
func consumer(ch <-chan int, wg *sync.WaitGroup) { wg.Add(1) defer wg.Done() for i := range ch { fmt.Println(i) } } func producer(size int) { queue := make(chan int) wg := new(sync.WaitGroup) go consumer(queue, wg) go consumer(queue, wg) for i := 0; i < size; i++ { queue <- i } close(queue) wg.Wait() }
func generator(n int) <-chan int { out := make(chan int) go func() { defer close(out) for i := 0; i < n; i++ { out <- i } }() return out } func double(in <-chan int) <-chan int { out := make(chan int) go func() { defer close(out) for i := range in { out <- i * 2 } }() return out } func print(in <-chan int) { for i := range in { fmt.Println(i) } } func main() { ch1 := generator(10) ch2 := double(ch1) print(ch2) }
// Send the sequence 2, 3, 4, ... to channel 'ch'. func Generate(ch chan<- int) { for i := 2; ; i++ { ch <- i // Send 'i' to channel 'ch'. } } // Copy the values from channel 'in' to channel 'out', // removing those divisible by 'prime'. func Filter(in <-chan int, out chan<- int, prime int) { for { i := <-in // Receive value from 'in'. if i%prime != 0 { out <- i // Send 'i' to 'out'. } } } // The prime sieve: Daisy-chain Filter processes. func main() { ch := make(chan int) // Create a new channel. go Generate(ch) // Launch Generate goroutine. for i := 0; i < 10; i++ { prime := <-ch fmt.Println(prime) ch1 := make(chan int) go Filter(ch, ch1, prime) ch = ch1 } } 62
// in => 前のFilter(Generator)から数値を渡されるChannel // out => 次のFilterに数値を渡すChannel // prime => Filterに設定される素数 func Filter(in <-chan int, out chan<- int, prime int) { for { i := <-in // Filter(Generator)から数値が渡ってくる if i%prime != 0 { out <- i // 自身に渡された素数で割り切れないもの次のFilterに送る } } } 65
func fetch(url string) int { res, _ := http.Get(url) return res.StatusCode } func crawl(urls []string) { m := make(map[int]int) for _, url := range urls { status := fetch(url) m[status]++ } } ~/w/g/s/g/c/g/p/crawler ››› go build; time ./crawler -n 100 ./crawler -n 100 0.08s user 0.12s system 0% cpu 30.554 total ฒߦॲཧͳ͠
func crawl(urls []string) { m := make(map[int]int) // statusを受信するChannel ch := make(chan int) for _, url := range urls { go func() { // ここが並行処理 ch <- fetch(url) }() } // urlsの数だけchから読み取る for range urls { m[<-ch]++ } } ~/w/g/s/g/c/g/p/crawler ››› go build; time ./crawler -n 100⏎ ./crawler -n 100 0.04s user 0.03s system 20% cpu 0.338 total ඵ͔Β NT ·Ͱॖ
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