关于使用线程的排序速度

关于使用线程的排序速度

线程

/*************************************************************************

> File Name: t.cpp

> Author: Function_Dou

> Mail:

> Created Time: 2018年02月07日 星期三 18时51分14秒

************************************************************************/

#include <stdio.h>

#include <pthread.h>

#include "apue.h"

#include <sys/time.h>

const int Max = 30000;

const int max = Max - 1;

long arr[Max];

long arr1[Max];

void Sort(long *arr, int num)

{

int i, j, t;

for (i = 0; i < max; i++)

for(j = i + 1; j < Max; j++)

if(num == 0)

{

if(arr[i] < arr[j])

{

t = arr[i];

arr[i] = arr[j];

arr[j] = t;

}

}

else

if(arr[i] > arr[j])

{

t = arr[i];

arr[i] = arr[j];

arr[j] = t;

}

}

void *SortThread(void *)

{

Sort(arr, 0);

pthread_exit((void *)1);

}

void *SortThread2(void *)

{

Sort(arr1, 1);

pthread_exit((void *)1);

}

int main(void)

{

int i;

struct timeval start, end;

// 线程开始的计时

gettimeofday(&start, NULL);

// 生成大量随机数, 用于排序

srandom(1);

for(i = 0; i < Max; i++)

{

arr[i] = random();

arr1[i] = i;

}

// 一个进行随机排序. 一个最坏情况的排序

pthread_t threadid1, threadid2;

pthread_create(&threadid1, NULL, SortThread, NULL);

pthread_create(&threadid2, NULL, SortThread, NULL);

// 线程的结束时间

gettimeofday(&end, NULL);

// 时间的差值计算

printf("pthread no time is : %.4f\n", (double)(end.tv_sec * 1000000 + end.tv_usec - (start.tv_sec * 1000000 - start.tv_usec)) / 1000000);

// ------------------------------------

// 没有线程的排序计时

gettimeofday(&start, NULL);

for(i = 0; i < Max; i++)

arr[i] = random();

// 一个进行随机排序. 一个最坏情况的排序

Sort(arr, 0);

Sort(arr1, 1);

// 线程的结束时间

gettimeofday(&end, NULL);

// 时间的差值计算

printf("pthread no time is : %.4f\n", (double)(end.tv_sec * 1000000 + end.tv_usec - (start.tv_sec * 1000000 - start.tv_usec)) / 1000000);

exit(0);

}

[root@localhost Pthread]# ./a.out

pthread no time is : 2.0003

pthread no time is : 3.7875

[root@localhost Pthread]# ./a.out

pthread no time is : 0.4818

pthread no time is : 4.2071

[root@localhost Pthread]# ./a.out

pthread no time is : 1.4883

pthread no time is : 5.2815

[root@localhost Pthread]# ./a.out

pthread no time is : 0.9232

pthread no time is : 4.6768

[root@localhost Pthread]# ./a.out

pthread no time is : 0.7061

pthread no time is : 3.5253

[root@localhost Pthread]# ./a.out

pthread no time is : 0.4698

pthread no time is : 3.4451

[root@localhost Pthread]# ./a.out

pthread no time is : 1.8373

pthread no time is : 4.7519

[root@localhost Pthread]# ./a.out

pthread no time is : 0.6393

pthread no time is : 3.3885