英文:
concurrency in go -Taking same time with different no of CPU
问题
我正在运行一个并发的Go程序，根据下面的两个案例观察到，无论使用多少个CPU，执行时间都是相同的。
案例1：当cpuUsed = 1时，
程序执行时间为3m20.973185s。
当我增加使用的CPU数量时，
案例2：当cpuUsed = 8时，
程序执行时间为3m20.9330516s。
请查看以下Go代码以获取更多详细信息。
package main
import (
"fmt"
"math/rand"
"runtime"
"sync"
"time"
)
var waitG sync.WaitGroup
var cpuUsed = 1
var maxRandomNums = 1000
func init() {
maxCPU := runtime.NumCPU() //它将给出最大的CPU数量 :)
cpuUsed = 8 //对于1和8，花费的时间相同
runtime.GOMAXPROCS(cpuUsed)
fmt.Printf("CPU数量（总共=%d - 使用=%d）\n", maxCPU, cpuUsed)
}
func main() {
start := time.Now()
ids := []string{"rotine1", "routine2", "routine3", "routine4"}
waitG.Add(4)
for i := range ids {
go numbers(ids[i])
}
waitG.Wait()
elapsed := time.Since(start)
fmt.Printf("\n程序执行时间为%s。\n", elapsed)
}
func numbers(id string) {
rand.Seed(time.Now().UnixNano())
for i := 1; i <= maxRandomNums; i++ {
time.Sleep(200 * time.Millisecond)
fmt.Printf("%s-%d ", id, rand.Intn(20)+20)
}
waitG.Done()
}
英文:
I am running a go concurrent program with the below two case and observed that It is taking same time irrespective of no of CPU it using while execution.
Case1: When cpuUsed = 1
program took 3m20.973185s.
when I am increasing the no of CPU used.
Case2: when cpuUsed = 8
program took 3m20.9330516s.
Please find the below Go code for more details.
package main
import (
"fmt"
"math/rand"
"runtime"
"sync"
"time"
)
var waitG sync.WaitGroup
var cpuUsed = 1
var maxRandomNums = 1000
func init() {
maxCPU := runtime.NumCPU() //It'll give us the max CPU :)
cpuUsed = 8 //getting same time taken for 1 and 8
runtime.GOMAXPROCS(cpuUsed)
fmt.Printf("Number of CPUs (Total=%d - Used=%d) \n", maxCPU, cpuUsed)
}
func main() {
start := time.Now()
ids := []string{"rotine1", "routine2", "routine3", "routine4"}
waitG.Add(4)
for i := range ids {
go numbers(ids[i])
}
waitG.Wait()
elapsed := time.Since(start)
fmt.Printf("\nprogram took %s. \n", elapsed)
}
func numbers(id string) {
rand.Seed(time.Now().UnixNano())
for i := 1; i <= maxRandomNums; i++ {
time.Sleep(200 * time.Millisecond)
fmt.Printf("%s-%d ", id, rand.Intn(20)+20)
}
waitG.Done()
}
答案1
得分: 1
你会发现：
总时间（3分20秒）= 200秒 = sleep(200毫秒) * 循环次数(1000)
让我们简化你的代码并关注CPU使用率：
- 移除不使用CPU的Sleep。
- fmt.Println作为stdio，不使用CPU。
- 随机数没有做任何事情，只是引入了不确定性，移除它。
- goroutine中唯一消耗CPU的代码是"rand.Intn(20)+20"，将其变为常量相加。
- 增加"maxRandomNums"的值。
然后你的代码将变成这样，再次运行它：
package main
import (
"fmt"
"runtime"
"sync"
"time"
)
var waitG sync.WaitGroup
var cpuUsed = 1
var maxRandomNums = 1000000000
func init() {
maxCPU := runtime.NumCPU() //It'll give us the max CPU :)
cpuUsed = 8 //getting same time taken for 1 and 8
runtime.GOMAXPROCS(cpuUsed)
fmt.Printf("Number of CPUs (Total=%d - Used=%d) \n", maxCPU, cpuUsed)
}
func main() {
start := time.Now()
ids := []string{"rotine1", "routine2", "routine3", "routine4"}
waitG.Add(4)
for i := range ids {
go numbers(ids[i])
}
waitG.Wait()
elapsed := time.Since(start)
fmt.Printf("\nprogram took %s. \n", elapsed)
}
func numbers(id string) {
// rand.Seed(time.Now().UnixNano())
for i := 1; i <= maxRandomNums; i++ {
// time.Sleep(200 * time.Millisecond)
// fmt.Printf("%s-%d ", id, rand.Intn(20)+20)
_ = i + 20
}
waitG.Done()
}
英文:
you will find out:
total time (3 min 20s) = 200s = sleep(200ms) * loops(1000)
Let's simplify your code and focus on CPU usage:
- Remove the Sleep, which does not use the CPU at all
- fmt.Println as a stdio, does not use the CPU
- Random number did nothing but introduce uncertainty into the program, remove it
- The only code that takes CPU in the goroutine is the "rand.Intn(20)+20", making it a constant addition
- Increase the "maxRandomNums"
then your code will be like this, run it again
package main
import (
"fmt"
"runtime"
"sync"
"time"
)
var waitG sync.WaitGroup
var cpuUsed = 1
var maxRandomNums = 1000000000
func init() {
maxCPU := runtime.NumCPU() //It'll give us the max CPU :)
cpuUsed = 8 //getting same time taken for 1 and 8
runtime.GOMAXPROCS(cpuUsed)
fmt.Printf("Number of CPUs (Total=%d - Used=%d) \n", maxCPU, cpuUsed)
}
func main() {
start := time.Now()
ids := []string{"rotine1", "routine2", "routine3", "routine4"}
waitG.Add(4)
for i := range ids {
go numbers(ids[i])
}
waitG.Wait()
elapsed := time.Since(start)
fmt.Printf("\nprogram took %s. \n", elapsed)
}
func numbers(id string) {
// rand.Seed(time.Now().UnixNano())
for i := 1; i <= maxRandomNums; i++ {
// time.Sleep(200 * time.Millisecond)
// fmt.Printf("%s-%d ", id, rand.Intn(20)+20)
_ = i + 20
}
waitG.Done()
}
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