第5章_Goroutine

5-1 goroutine.mp4

package main
import "fmt"
func main() {
    //fmt.Printf("hellow from goroutine %d")
    for i := 0; i < 10; i++ {
        go func(ii int) {
            for {
                fmt.Printf("hellow from goroutine %d\n", ii)
            }
        }(i)
    }
    select {}
}

携程
Coroutine

• 轻量级”线程”
• 非抢占式 多任务处理,由携程主动交出控制权 ``` package main

import ( “fmt” “time” )

func main() { //fmt.Printf(“hellow from goroutine %d”) var a [10]int for i := 0; i < 10; i++ { go func(i int) { for { a[i]++ //fmt.Printf(“hellow from goroutine %d\n”, ii) } }(i) } time.Sleep(time.Millisecond) fmt.Println(a) } /** [452860 456018 32360 77853 13509 368659 62929 151728 74805 319663]

Process finished with the exit code 0 */

```
package main
import (
    "fmt"
    "runtime"
    "time"
)
func main() {
    //fmt.Printf("hellow from goroutine %d")
    var a [10]int
    for i := 0; i < 10; i++ {
        go func(i int) {
            for {
                a[i]++
                //fmt.Printf("hellow from goroutine %d\n", ii)
                // 交出控制权
                runtime.Gosched()
            }
        }(i)
    }
    time.Sleep(time.Millisecond)
    fmt.Println(a)
}
/**
[655 669 635 667 532 582 608 503 578 539]
Process finished with the exit code 0
 */

不明觉厉,他们有什么区别???

如果不传递i
会发生:

package main
import (
    "fmt"
    "runtime"
    "time"
)
func main() {
    //fmt.Printf("hellow from goroutine %d")
    var a [10]int
    for i := 0; i < 10; i++ {
        go func() {
            // race condition
            for {
                a[i]++
                //fmt.Printf("hellow from goroutine %d\n", ii)
                // 交出控制权
                runtime.Gosched()
            }
        }()
    }
    time.Sleep(time.Millisecond)
    fmt.Println(a)
}
/**
PS E:\Projects\GolandProjects\go-camp\mooc\code\learngo\goroutine> go run .\goroutine.go -race
panic: runtime error: index out of range [10] with length 10
goroutine 15 [running]:
main.main.func1()
        E:/Projects/GolandProjects/go-camp/mooc/code/learngo/goroutine/goroutine.go:16 +0x56
created by main.main
        E:/Projects/GolandProjects/go-camp/mooc/code/learngo/goroutine/goroutine.go:13 +0x57
panic: runtime error: index out of range [10] with length 10
goroutine 10 [running]:
main.main.func1()
        E:/Projects/GolandProjects/go-camp/mooc/code/learngo/goroutine/goroutine.go:16 +0x56
created by main.main
        E:/Projects/GolandProjects/go-camp/mooc/code/learngo/goroutine/goroutine.go:13 +0x57
exit status 2
PS E:\Projects\GolandProjects\go-camp\mooc\code\learngo\goroutine>
 */

5-2 go语言的调度器.mp4

携程特点

• 轻量级的线程
• 非抢占式多任务处理,有携程主动交出控制权
• 编译器/解释器/虚拟机层面的多任务
• 多个携程可能在一个或者多个线程上运行

• 任何函数只需加上go就能送给调度器运行
• 不需要在定义时区分是否是异步函数
• 调度器在合适的点进行切换
• 使用-race来检测数据访问冲突