Concurrence

goroutine is the core of Go's concurrence

package main
import ( "fmt" "runtime")
func say(s string)
{ for i := 0;i<5;i++{ 
 runtime.Gosched() 
 fmt.Println(s) 
}
}
func main()
{ go say("world") say("hello")}

Here is the output

// hello// world// hello// world// hello// world// hello// world// hello

• runtime.Gosched() means letting CPU give out the controling right, resume next time.

channels

channel is a great mechanism for sharing the memories.

establish a channel:

ci := make(chan int)cs := make(chan string)cf := make(chan interface{})

channel receive and send data by <-

ch <- v //send v to channel chv := <-ch //receive data from ch and assign to v

Here is an example:

package mainimport "fmt"func sum(a []int,c chan int){ total := 0 for _, v := range a{ total += v } c <- total }func main(){ a := []int{3,25,6,4,8,1} c := make(chan int) go sum(a[:len(a)/2],c) go sum(a[len(a)/2:],c) x,y := <-c,<-c fmt.Println(x,y,x+y)}

Blockage:

When reading from the channel(value <- chan), it will get blocked till its data got received.

When sending data (ch <- 5) to the channel, it will get blocked till data get read.

No explicit locks are needed.

Non-buffer character makes the concurrence more effective.

Buffered channels

The golang also permmits your assigning buffer's space:

ch := make(chan type, value)

package mainimport "fmt"func main(){ c := make(chan int,2) c <- 1 c <- 2 fmt.Println(<-c) fmt.Println(<-c)}

The output should be :

12

First in, first out.

Range and close

package mainimport( "fmt")func fibonacci(n int, c chan int){ x,y := 1,1 for i := 0;i<n;i++{ c <- x x,y = y,x+y } close(c) //close the channel}func main(){ c := make(chan int,10) go fubonacci(cap(c),c) //cap(c) means the capacity of this channel for i := range c{ fmt.Println(i) }}

Select

We can use select to monitor the data flow on one interested channel.

package mainimport "fmt"func fibonacci(c,quit chan int){ x, y := 1,1 for { select { case c <- x: x, y = y, x+y case c <- quit: fmt.Println("quit") return } }}func main(){ c := make(chan int) quit := make(chan int) go func() { for i := 0;i<10;i++{ fmt.Println(<-c) } quit <- 0 }() fibnacci(c,quit)}

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