Question

I have three functions which prints First, Second and Third. I want to print it in the order First then Second and then Third via concurrency (channels)

我正面临着按顺序排列的问题。谁能帮助我如何实现秩序?

package main

import (
    "fmt"
    "sync"
)

type firstSecondThird struct {
    n int
}

var (
    wg     sync.WaitGroup
    first  chan bool
    second chan bool
    third  chan bool
)

func init() {
    first = make(chan bool)
    second = make(chan bool)
    // third = make(chan bool)
}

func (fn firstSecondThird) first() {
    defer wg.Done()
    for i := 0; i < fn.n; i++ {
        fmt.Print("First")
        first <- true
    }
}

func (fn firstSecondThird) second() {
    defer wg.Done()
    for i := 0; i < fn.n; i++ {
        <-first
        fmt.Print("Second")
        second <- true
    }
}

func (fn firstSecondThird) third() {
    defer wg.Done()
    for i := 0; i < fn.n; i++ {
        <-second
        fmt.Print("Third")
        // third <- true
    }
}

func main() {
    firstSecondThird := firstSecondThird{
        n: 4,
    }
    wg.Add(2)
    go firstSecondThird.first()
    go firstSecondThird.second()
    go firstSecondThird.third()
    // <-third
    wg.Wait()
}

<<>Output>:

FirstFirstSecondSecondFirstThirdThirdSecondThirdFirstSecond%

Answer 1

你们正在努力利用并非易事的渠道协调处决的次序。观察n processes:

for k>1, printing of k should happen after printing of k-1
for k=1, printing of k should happen after printing of n

因此,假体应当照此(k是功能指数):

 for i := 0; i < fn.n; i++ {
        if k==0 {
          <-ch[fn.n-1]
        } else {
          <-ch[k-1]
        }
        fmt.Print("Third")
        if k==fn.f-1 {
           ch[0]<-true
        } else {
           ch[k+1]<-true
        }
    }

Answer 2

package main

import (
    "fmt"
    "sync"
)

type firstSecondThird struct {
    n int
}

var (
    wg     sync.WaitGroup
    first  chan bool
    second chan bool
    third  chan bool
)

func init() {
    first = make(chan bool)
    second = make(chan bool)
    third = make(chan bool)
}

func (fn firstSecondThird) first() {
    for i := 0; i < fn.n; i++ {
        fmt.Print("First
")
        first <- true
        <-third
    }
    defer wg.Done()
}

func (fn firstSecondThird) second() {
    for i := 0; i < fn.n; i++ {
        <-first
        fmt.Print("Second
")
        second <- true
    }
    defer wg.Done()
}

func (fn firstSecondThird) third() {
    for i := 0; i < fn.n; i++ {
        <-second
        fmt.Print("Third
")
        third <- true
    }
    defer wg.Done()
}

func main() {
    firstSecondThird := firstSecondThird{
        n: 4,
    }
    wg.Add(3)
    go firstSecondThird.first()
    go firstSecondThird.second()
    go firstSecondThird.third()
    wg.Wait()
}

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