CPU_多线程操作图片_代码详解

Pthreads库

pthread_attr()初始化线程的各项属性

pthread_attr_setdetachstate()为初始化的线程设置属性

pthread_create()创建一个线程

pthread_attr_destroy()

pthread_join()合并线程

用于将任何给定的线程合并到最初创建它的线程中。你可以将“合并”过程想象成“毁灭”线程，或者父线程“吞食”刚刚创建的线程。

示例

main主函数被重复执行3次，每次执行使用2个线程完成计算任务。

#include<pthread.h>#include<stdint.h>#include<ctype.h>#include<stdlib.h>#include<stdio.h>#include<sys/time.h>#include<unistd.h>// sleep()函数头文件#defineREPS3#defineMAXTHREADS128longNumThreads=2;// Total number of threads working in parallel 并行的线程总数intThParam[MAXTHREADS];// Thread parameters ...线程参数pthread_tThHandle[MAXTHREADS];// Thread handles 线程句柄pthread_attr_tThAttr;// Pthread attrributesvoid*MTFlip(void*tid){inti;longts=*((int*)tid);// My thread ID is stored hereprintf("\ntid=%d\n",tid);for(i=0;i<3;i++){sleep(1);printf("\n 正在使用ts=%d 执行计算任务,循环到i=%d\n",tid,i);}pthread_exit(0);}intmain(intargc,char**argv){inta,i,ThErr;structtimevalt;doubleStartTime,EndTime;doubleTimeElapsed;if((NumThreads<1)||(NumThreads>MAXTHREADS)){printf("\nNumber of threads must be between 1 and %u... Exiting abruptly\n",MAXTHREADS);exit(EXIT_FAILURE);}else{if(NumThreads!=1){printf("\nExecuting the multi-threaded version with %li threads ...\n",NumThreads);}else{printf("\nExecuting the serial version ...\n");}}gettimeofday(&t,NULL);StartTime=(double)t.tv_sec*1000000.0+((double)t.tv_usec);if(NumThreads>1){for(a=0;a<REPS;a++){pthread_attr_init(&ThAttr);pthread_attr_setdetachstate(&ThAttr,PTHREAD_CREATE_JOINABLE);printf("\n 代码重复执行第 %d 次\n",a+1);for(i=0;i<NumThreads;i++){ThParam[i]=i;ThErr=pthread_create(&ThHandle[i],&ThAttr,MTFlip,(void*)&ThParam[i]);if(ThErr!=0){printf("\nThread Creation Error %d. Exiting abruptly... \n",ThErr);exit(EXIT_FAILURE);}}pthread_attr_destroy(&ThAttr);for(i=0;i<NumThreads;i++){pthread_join(ThHandle[i],NULL);}}}else{printf("\n单线程串行执行代码\n");}gettimeofday(&t,NULL);EndTime=(double)t.tv_sec*1000000.0+((double)t.tv_usec);TimeElapsed=(EndTime-StartTime)/1000.00;TimeElapsed/=(double)REPS;printf("\n\nTotal execution time: %9.4f ms ",TimeElapsed);return(EXIT_SUCCESS);}

toupper()小写字母转换为大写字母

C 库函数int toupper(int c)把小写字母转换为大写字母。
反参：
如果 c 有相对应的大写字母，则该函数返回 c 的大写字母，否则 c 保持不变。返回值是一个可被隐式转换为 char 类型的 int 值。

#include<stdio.h>#include<ctype.h>intmain(){inti=0;charstr[]="runoob";while(str[i]){putchar(toupper(str[i]));i++;}return(0);}

gettimeofday() 获取到当前时间的秒数

该函数的头文件在/usr/include/sys/time.h头文件中。

函数原型：int gettimeofday(struct timeval*tv, struct timezone *tz);

用到两个结构体：timeval和timezone

这两个结构体定义在/usr/include/linux/time.h头文件中。

示例2

#include<stdio.h>#include<sys/time.h>#include<unistd.h>intmain(){structtimevaltv;structtimezonetz;gettimeofday(&tv,&tz);printf("\ntv_sec; %d\n",tv.tv_sec);printf("tv_usec; %d\n",tv.tv_usec);printf("tz_minuteswest; %d\n",tz.tz_minuteswest);printf("tz_dsttime, %d\n",tz.tz_dsttime);}

示例2

#include<stdio.h>#include<sys/time.h>#include<unistd.h>// sleep()函数头文件#defineREPS1intmain(){structtimevalt;doubleStartTime,EndTime;doubleTimeElapsed;gettimeofday(&t,NULL);StartTime=(double)t.tv_sec*1000000.0+((double)t.tv_usec);sleep(30);//休眠30秒gettimeofday(&t,NULL);EndTime=(double)t.tv_sec*1000000.0+((double)t.tv_usec);TimeElapsed=(EndTime-StartTime)/1000.00;TimeElapsed/=(double)REPS;printf("\n\nTotal execution time: %9.4f ms ",TimeElapsed);}