current position:Home>[golang] walk into go language lesson 20 atomic operation & mutex
[golang] walk into go language lesson 20 atomic operation & mutex
2021-08-23 05:50:13 【I'm Xiaobai】
【Golang】️ Walk into Go Language ️ Lesson 20
summary
Golang Is a new cross platform programming language . Today, Xiaobai will take you hand in hand into Golang The world of . ( The first 20 course )
Problems in the process
When a large number of concurrent processes , There will be a resource preemption conflict .
Example :
package main
import (
"fmt"
"time"
)
func main() {
// Defines the atomic variable integer
var ops uint64 = 0
// Create a collaborative process
for i := 0; i < 10; i++ {
go func() {
for j := 0; j < 10000; j++ {
// Thread conflict , The data is not accurate
ops += 1
}
}()
}
// wait for
time.Sleep(time.Second * 5)
// Debug output
fmt.Println(ops)
}
Output results :
69980
We can see , The output is zero 69980, Instead of 100000, The reason is that the data is inaccurate due to thread conflict .
Atomic manipulation
atomic The atomic operation provided enables us to ensure that there is only one co process at any time (go routine) Operate on variables . Make good use of atomic It can avoid a large number of lock operations in the program .
Example :
package main
import (
"fmt"
"sync/atomic"
"time"
)
func main() {
// Defines the atomic variable integer
var ops uint64 = 0
//
for i := 0; i < 10; i++ {
go func() {
for j := 0; j < 10000; j++ {
// Avoid thread conflicts
atomic.AddUint64(&ops, 1)
}
}()
}
// wait for
time.Sleep(time.Second * 5)
// Debug output
fmt.Println(ops)
}
Output results :
100000
The mutex
The mutex (Mutex) Variables used for active control elements can only be accessed by one coroutine at a time .
Mutex There are two ways :
- func (*Mutex) Lock: Lock The method locks m, If m Locked , Then block to m Unlock
- func (*Mutex) Unlock: Unlock Method unlock m, If m Not locking will result in runtime errors
Example :
package main
import (
"fmt"
"math/rand"
"sync"
"sync/atomic"
"time"
)
func main() {
var state = make(map[int]int) // state
var mutex = &sync.Mutex{} // The mutex
var readops uint64 = 0 // Reading data
var writeops uint64 = 0 // Write data
// Cyclic reading
for i := 0; i < 100; i++ {
go func() {
total := 0
for {
key := rand.Intn(5)
mutex.Lock() // Lock
total += state[key] // Data overlay
mutex.Unlock() // Unlock
atomic.AddUint64(&readops, 1) // Record the number of reads
time.Sleep(time.Millisecond)
}
}()
}
// Loop write
for i := 0; i < 10; i++ {
go func() {
for {
key := rand.Intn(5)
val := rand.Intn(100)
mutex.Lock() // Lock
state[key] = val // Write data
mutex.Unlock() // Unlock
atomic.AddUint64(&writeops, 1) // Number of writes
time.Sleep(time.Millisecond)
}
}()
}
// Sleep 1 second
time.Sleep(time.Second * 1)
// Debug output
read := atomic.LoadUint64(&readops)
write := atomic.LoadUint64(&writeops)
fmt.Println(read)
fmt.Println(write)
mutex.Lock()
fmt.Println(state)
mutex.Unlock()
}
Output results :
5179
519
map[0:36 1:67 2:62 3:86 4:68]
copyright notice
author[I'm Xiaobai],Please bring the original link to reprint, thank you.
https://en.qdmana.com/2021/08/20210823055009369d.html
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