进程和线程
A。进程是程序在操作系统中的一次执行过程,系统进行资源分配和调度的一个独立单位。
B。线程是进程的一个执行实体,是CPU调度和分派的基本单位,它是比进程更小的能独立运行的基本单位。
C。一个进程可以创建和撤销多个线程;同一进程中的多个线程之间可以并发执行。
并发和并行
并发:多线程程序在一个核的cpu上运行
并行:多线程程序在多个核的cpu上运行
举例。。一个妈给一个碗给多个小孩喂饭,,是并发
一个妈给每个小孩一人一个碗,就是并行
并发 并行
协程和线程
协程:独立的栈空间,共享堆空间,调度由用户自己控制,本质上有点类似于用户级协程,这些用户级线程的调度也是自己实现的。
线程:一个线程上可以跑多个协程,协程是轻量级的线程。
例子
package main
import (
"fmt"
"time"
)
func test() {
var i int
for {
fmt.Println(i)
time.Sleep(time.Second)
i++
}
}
func main() {
go test() //起一个协程执行test()
for {
fmt.Println("i : runnging in main")
time.Sleep(time.Second )
}
}
-
--
设置Golang运行的cpu核数。
1.8版本以上,默认跑多个核
package main
import (
"fmt"
"runtime"
)
func main() {
num := runtime.NumCPU()
runtime.GOMAXPROCS(num)
fmt.Println(num)
}
并发计算
package main
import (
"fmt"
"sync"
"time"
)
var (
m = make(map[int]uint64)
lock sync.Mutex
)
type task struct {
n int
}
func calc(t *task) {
var sum uint64
sum = 1
for i := 1; i < t.n; i++ {
sum *= uint64(i)
}
fmt.Println(t.n, sum)
lock.Lock()
m[t.n] = sum
lock.Unlock()
}
func main() {
for i := 0; i < 16; i++ {
t := &task{n: i}
go calc(t)//并发执行,谁快谁先出
}
time.Sleep(10 * time.Second)
//lock.Lock()
//for k, v := range m {
// fmt.Printf("%d!=%v\n", k, v)
//}
//lock.Unlock()
}
channel概念
a。类似unix中的管道(pipe)
b.先进先出
c。线程安全,多个goroutine同时访问,不需要枷锁
d。channel是有类型的,一个整数的channel只能存整数
channel声明
var name chan string
var age chan int
var mapchan chan map[string]string
var test chan student
var test1 chan *student
channel初始化
使用make进行初始化
var test chan int
test = make(chan int,10)
var test chan string
test=make(chan string,10)
channel基本操作
从channel读取数据
var testChan chan int
testChan = make(chan int, 10)
var a int
a = <-testChan
-从channel写入数据
var testChan chan int
testChan = make(chan int, 10)
var a int = 10
testChan <- a
第一个例子
package main
import "fmt"
type student struct {
name string
}
func main() {
var stuChan chan *student
stuChan = make(chan *student, 10)
stu := student{name: "stu001"}
stuChan <- &stu
var stu01 interface{}
stu01 = <-stuChan
var stu02 *student
stu02, ok := stu01.(*student)
if !ok {
fmt.Println("can not convert")
return
}
fmt.Println(stu02)
}
package main
import (
"fmt"
"time"
)
//起一个读的协程
func write(ch chan int) {
for i := 0; i < 1000; i++ {
ch <- i
}
}
func read(ch chan int) {
for {
var b int
b = <-ch
fmt.Println(b)
}
}
func main() {
intChan := make(chan int, 10)
go write(intChan)
go read(intChan)
time.Sleep(10 * time.Second)
}
读,取,字符串
package main
import (
"fmt"
"time"
)
func sendData(ch chan string) {
ch <- "Washington"
ch <- "Tripoli"
ch <- "London"
ch <- "Beijing"
ch <- "Tokio"
}
func getData(ch chan string) {
var input string
for {
input = <-ch
fmt.Println(input)
}
}
func main() {
ch := make(chan string)
go sendData(ch)
go getData(ch)
time.Sleep(3 * time.Second)
}
只能放一个元素的testChan
var testChan chan int
testChan = make(chan int)
var a int
a = <-testChan
-
testChan是带缓冲区的chan,一次可以放10个元素
var testChan chan int
testChan = make(chan int, 10)
var a int = 10
testChan <- a
-
package main
import (
"fmt"
"sync"
"time"
)
var (
m = make(map[int]uint64)
lock sync.Mutex
)
type task struct {
n int
}
func calc(t *task) {
var sum uint64
sum = 1
for i := 1; i < t.n; i++ {
sum *= uint64(i)
}
fmt.Println(t.n, sum)
lock.Lock()
m[t.n] = sum
lock.Unlock()
}
func main() {
for i := 0; i < 16; i++ {
t := &task{n: i}
go calc(t)
}
time.Sleep(10 * time.Second)
lock.Lock()
for k, v := range m {
fmt.Printf("%d!=%v\n", k, v)
}
lock.Unlock()
}
package main
import (
"fmt"
)
func calc(taskChan chan int, resChan chan int, exitChan chan bool) {
for v := range taskChan {
flag := true
for i := 2; i < v; i++ {
if v%i == 0 {
flag = false
break
}
}
if flag {
resChan <- v
}
}
fmt.Println("exit")
exitChan <- true
}
func main() {
intChan := make(chan int, 1000)
resultChan := make(chan int, 1000)
exitChan := make(chan bool, 8)
go func() {
for i := 0; i < 10000; i++ {
intChan <- i
}
close(intChan)
}()
for i := 0; i < 8; i++ {
go calc(intChan, resultChan, exitChan)
}
//等待所有计算的goroutine全部退出
go func() {
for i := 0; i < 8; i++ {
<-exitChan
fmt.Println("wait goroute", i, "exited")
}
close(resultChan)
}()
for v := range resultChan {
fmt.Println(v)
}
}
package main
import "fmt"
func send(ch chan int, exitChan chan struct{}) {
for i := 0; i < 10; i++ {
ch <- i
}
close(ch)
var a struct{}
exitChan <- a
}
func recv(ch chan int, exitChan chan struct{}) {
for {
v, ok := <-ch
if !ok {
break
}
fmt.Println(v)
}
var a struct{}
exitChan <- a
}
func main() {
var ch chan int
ch = make(chan int, 10)
exitChan := make(chan struct{}, 2)
go send(ch, exitChan)
go recv(ch, exitChan)
var total = 0
for _ = range exitChan {
total++
if total == 2 {
break
}
}
}
package main
import "fmt"
func main() {
var ch chan int
ch = make(chan int, 10)
for i := 0; i < 10; i++ {
ch <- i
}
close(ch)
for {
var b int
b, ok := <-ch
//检测管道是否关闭
if ok == false {
fmt.Println("chan is close")
break
}
fmt.Println(b)
}
}
1. 使用内置函数close进行关闭,chan关闭之后,for range遍历chan中
已经存在的元素后结束
2. 使用内置函数close进行关闭,chan关闭之后,没有使用for range的写法
需要使用,v, ok := <- ch进行判断chan是否关闭
只读的声明
Var 变量的名字 <-chan int
Var readChan <- chan int
只写的声明
Var 变量的名字 chan<- int
Var writeChan chan<- int
package main
import "fmt"
//只写chan
func send(ch chan<- int, exitChan chan struct{}) {
for i := 0; i < 10; i++ {
ch <- i
}
close(ch)
var a struct{}
exitChan <- a
}
//只读chan
func recv(ch <-chan int, exitChan chan struct{}) {
for {
v, ok := <-ch
if !ok {
break
}
fmt.Println(v)
}
var a struct{}
exitChan <- a
}
func main() {
var ch chan int
ch = make(chan int, 10) //初始化chan
exitChan := make(chan struct{}, 2)
go send(ch, exitChan)
go recv(ch, exitChan)
var total = 0
for _ = range exitChan {
total++
if total == 2 {
break
}
}
}
不阻塞
package main
import "fmt"
import "time"
func main() {
var ch chan int
ch = make(chan int, 10)
ch2 := make(chan int, 10)
go func() {
var i int
for {
ch <- i
time.Sleep(time.Second)
ch2 <- i * i
time.Sleep(time.Second)
i++
}
}()
for {
select {
case v := <-ch:
fmt.Println(v)
case v := <-ch2:
fmt.Println(v)
case <-time.After(time.Second):
fmt.Println("get data timeout")
time.Sleep(time.Second)
}
}
}