博客

C语言：

[root@localhost efficient]# cat calc_c.c
#include<stdio.h>
#include<time.h>

int  main(char** argv, char argc)
{
    int second1,second2;
    long long i; 
    long long count;

    second1 = time((time_t*)NULL);
    count = 0;
    for (i = 0 ; i < 9000000000ll; i++){
        count += i;
    }       
    second2 = time((time_t*)NULL);
    printf("cost:%d,count:%lld\n", second2 - second1, count);

    return 0;
}

[root@localhost efficient]# make calc_c
cc     calc_c.c   -o calc_c
[root@localhost efficient]# ./calc_c
cost:57,count:3606511848080896768

golang：

[root@localhost efficient]# cat calc_go.go
package main

import "fmt"
import "time"

func main(){

    t1 := time.Now()
    count :=int64(0) 
    max := int64(9000000000)
    for i :=int64(0); i< max; i++{
        count += i

    }   
    t2 := time.Now()
    fmt.Printf("cost:%d,count:%d\n",t2.Sub(t1)/1000000000,count)

}
[root@localhost efficient]# go build calc_go.go
[root@localhost efficient]# ./calc_go
cost:52,count:3606511848080896768

基本一致，c用时57s，go用时52s。

下面加入简单Coroutine尝试

[root@localhost efficient]# cat calc_coroutine.go
package main

import "fmt"
import "runtime"
import "time"

func  run(i,n int64 ,ch chan int64){
    count := int64(0)
    for i := int64(i); i < n; i++ {
        count = count +i
    }   
    ch <- count

}

func main(){

    t1 := time.Now()
    NCPU := runtime.NumCPU()
    fmt.Printf("NCPU:%d\n",NCPU)
    runtime.GOMAXPROCS(NCPU)
    chs := make([] chan int64,NCPU)
    for i :=int64(0); i < int64(NCPU); i++{
        chs[i] = make(chan int64)
        n := int64(9000000000)/int64(NCPU)
        go run(i*n, (i+1)*n,chs[i])
    }   

    count := int64(0)
    for i :=0; i < NCPU;i++{
        t := <- chs[i]
        count = count +t
    }   
    t2 := time.Now()

    fmt.Printf("cpu num:%d,cost:%d,count:%d\n",NCPU,t2.Sub(t1)/1000000000,count)
}
[root@localhost efficient]# go build calc_coroutine.go
[root@localhost efficient]# ./calc_coroutine
NCPU:2
cpu num:2,cost:34,count:3606511848080896768

用时34s，确实提高了，关键是实现很简单