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用Pthreads进程共享内存编程

用Pthreads进程共享内存编程

作者: Superbsco | 来源:发表于2017-12-02 11:39 被阅读11次

更多的可以参考我的博客，也在陆续更新ing
http://www.hspweb.cn/

1、用VIM编写创建一个进程的代码，每隔一秒递增输出1-5。

#include <pthread.h>
#include <stdio.h>
void* fun(void* rank){
    int i;
    int my_rank=(int)rank;
    for(i=1;i<=5;i++){
        printf("Thread %d:%d\n",my_rank,i);
        sleep(1);
    }
    pthread_exit(0);
}
int main(){
  pthread_t tid1;   //the 2 thread identifier
  int num1=0;

  //create the thread
  pthread_create(&tid1,NULL,fun,(void *)num1);

  //now wait for the thread to exit
  pthread_join(tid1,NULL);
}
image

2、用VIM编写创建两个进程的代码，每隔一秒递增输出1-5。

#include <pthread.h>
#include <stdio.h>
void* fun(void* rank){
    int i;
    int my_rank=(int)rank;
    for(i=1;i<=5;i++){
        printf("Thread %d:%d\n",my_rank,i);
        sleep(1);
    }
    pthread_exit(0);
}
int main(){
  pthread_t tid1,tid2;  //the 2 thread identifier
  int num1=0,num2=1;

  //create the thread
  pthread_create(&tid1,NULL,fun,(void *)num1);
  pthread_create(&tid2,NULL,fun,(void *)num2);
  //now wait for the thread to exit
  pthread_join(tid1,NULL);
  pthread_join(tid2,NULL);
}
image

3、用VIM编写创建两个进程计算π的代码，观察竞争条件。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <math.h>
int n,thread_count;
double sum=0.0;

void* Thread_sum(void* rank){

    long my_rank=(long)rank;
    double factor;
    long long i;
    long long my_n=n/thread_count;
    long long my_first_i=my_n*my_rank;
    long long my_last_i=my_first_i+my_n;

    if(my_first_i % 2==0 ){
        factor=1.0;
    }else{
        factor=-1.0;
    }
    for(i=my_first_i;i<my_last_i;i++,factor=-factor){
        sum+=factor/(2*i+1);
    }
    return NULL;
}

int main(int argc,char* argv[]){
    long long i;
    //scanf("%d%d",&thread_count,&n);
    thread_count=atoi(argv[1]);
    n=atoi(argv[2]);
    //printf("%d\n%d\n",thread_count,n);
    //printf("%d\n%d\n%d\n",argc,argv[0],argv[1],argv[2]);
    printf("With n=%d terms\n",n);
    pthread_t thread_handles[thread_count];
    for(i=0;i<thread_count;i++){
        pthread_create(&thread_handles[i],NULL,Thread_sum,(void *)i);
    }
    for(i=0;i<thread_count;i++){
        pthread_join(thread_handles[i],NULL);
    }
    printf("our estimate of  pi = %.15lf\n",4*sum);
    sum=0;
    pthread_create(&thread_handles[0],NULL,Thread_sum,(void *)0);
    pthread_join(thread_handles[0],NULL);
    printf("Single thread of pi = %.15lf\n",4*sum);
    printf("                 pi = %.15lf\n",4*atan(1.0));
    return 0; 
}
image

4、用忙等待互斥（严格轮换法）解决计算π的竞争条件。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <math.h>
#include "timer.h"
int n,thread_count;
double sum=0.0;
int flag=0;
void* Thread_sum(void* rank){
    long my_rank=(long)rank;
    double factor,my_sum=0.0;
    long long i;
    long long my_n=n/thread_count;
    long long my_first_i=my_n*my_rank;
    long long my_last_i=my_first_i+my_n;

    if(my_first_i % 2==0 ){
        factor=1.0;
    }else{
        factor=-1.0;
    }
    for(i=my_first_i;i<my_last_i;i++,factor=-factor){
        my_sum+=factor/(2*i+1);
    }
    while(flag!=my_rank);
    sum+=my_sum;
    flag=(flag+1)%thread_count;
    // pthread_exit(NULL);
    return NULL;
}
int main(int argc,char* argv[]){
    double start, finish, elapsed;
    long long i;
    //scanf("%d%d",&thread_count,&n);
    thread_count=atoi(argv[1]);
    n=atoi(argv[2]);
    //printf("%d\n%d\n",thread_count,n);
    //printf("%d\n%d\n%d\n",argc,argv[0],argv[1],argv[2]);
    printf("With n=%d terms\n",n);
    pthread_t thread_handles[thread_count];
    GET_TIME(start);
    for(i=0;i<thread_count;i++){
        pthread_create(&thread_handles[i],NULL,Thread_sum,(void *)i);
    }
    for(i=0;i<thread_count;i++){
        pthread_join(thread_handles[i],NULL);
    }
    GET_TIME(finish);
    printf("    Multi-threaded estimate of  pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time = %e seconds\n", elapsed);

    sum=0;
    GET_TIME(start);
    pthread_create(&thread_handles[0],NULL,Thread_sum,(void *)0);
    pthread_join(thread_handles[0],NULL);
    GET_TIME(finish);
    printf("    Single-threaded estimate of pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time= %e seconds\n",elapsed);
    printf("    Math library estimate of    pi = %.15lf\n",4*atan(1.0));
    return 0;
}
image

5、用Peterson解法解决计算π的竞争条件。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <math.h>
#include "timer.h"
int n,thread_count;
double sum=0.0;

int turn;
int interested[2];

void* Thread_sum(void* rank){
    long my_rank=(long)rank;
    double factor,my_sum=0.0;
    long long i;
    long long my_n=n/thread_count;
    long long my_first_i=my_n*my_rank;
    long long my_last_i=my_first_i+my_n;

    int other;
    other=(my_rank+1)%2;
    interested[my_rank]=1;

    if(my_first_i % 2==0 ){
        factor=1.0;
    }else{
        factor=-1.0;
    }
    for(i=my_first_i;i<my_last_i;i++,factor=-factor){
        my_sum+=factor/(2*i+1);
    }
    turn=my_rank;
    while(turn==my_rank && interested[other]==1);
    sum+=my_sum;
    interested[my_rank]=0;
    // pthread_exit(NULL);
    return NULL;
}
int main(int argc,char* argv[]){
    double start, finish, elapsed;
    long long i;
    //scanf("%d%d",&thread_count,&n);
    thread_count=atoi(argv[1]);
    n=atoi(argv[2]);
    //printf("%d\n%d\n",thread_count,n);
    //printf("%d\n%d\n%d\n",argc,argv[0],argv[1],argv[2]);
    printf("With n=%d terms\n",n);
    pthread_t thread_handles[thread_count];
    GET_TIME(start);
    for(i=0;i<thread_count;i++){
        pthread_create(&thread_handles[i],NULL,Thread_sum,(void *)i);
    }
    for(i=0;i<thread_count;i++){
        pthread_join(thread_handles[i],NULL);
    }
    GET_TIME(finish);
    printf("     Peterson estimate of       pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time = %e seconds\n", elapsed);

    sum=0;
    GET_TIME(start);
    pthread_create(&thread_handles[0],NULL,Thread_sum,(void *)0);
    pthread_join(thread_handles[0],NULL);
    GET_TIME(finish);
    printf("    Single-threaded estimate of pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time= %e seconds\n",elapsed);
    printf("    Math library estimate of    pi = %.15lf\n",4*atan(1.0));
    return 0;
}
image

6、用互斥量解决计算π的竞争条件。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <math.h>
#include "timer.h"
int n,thread_count;
double sum=0.0;
pthread_mutex_t mutex;

void* Thread_sum(void* rank){
    long my_rank=(long)rank;
    double factor,my_sum=0.0;
    long long i;
    long long my_n=n/thread_count;
    long long my_first_i=my_n*my_rank;
    long long my_last_i=my_first_i+my_n;

    if(my_first_i % 2==0 ){
        factor=1.0;
    }else{
        factor=-1.0;
    }
    for(i=my_first_i;i<my_last_i;i++,factor=-factor){
        my_sum+=factor/(2*i+1);
    }
    pthread_mutex_lock(&mutex);
    sum+=my_sum;
    pthread_mutex_unlock(&mutex);

    // pthread_exit(NULL);
    return NULL;
}
int main(int argc,char* argv[]){
    double start, finish, elapsed;
    long long i;
    //scanf("%d%d",&thread_count,&n);
    thread_count=atoi(argv[1]);
    n=atoi(argv[2]);
    //printf("%d\n%d\n",thread_count,n);
    //printf("%d\n%d\n%d\n",argc,argv[0],argv[1],argv[2]);
    printf("With n=%d terms\n",n);
    pthread_t thread_handles[thread_count];
    GET_TIME(start);
     for(i=0;i<thread_count;i++){
        pthread_create(&thread_handles[i],NULL,Thread_sum,(void *)i);
    }
    for(i=0;i<thread_count;i++){
        pthread_join(thread_handles[i],NULL);
    }
    GET_TIME(finish);
    printf("                   estimate of  pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time = %e seconds\n", elapsed);

    sum=0;
    GET_TIME(start);
    pthread_create(&thread_handles[0],NULL,Thread_sum,(void *)0);
    pthread_join(thread_handles[0],NULL);
    GET_TIME(finish);
    printf("    Single-threaded estimate of pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time= %e seconds\n",elapsed);
    printf("    Math library estimate of    pi = %.15lf\n",4*atan(1.0));
    return 0;
}
image

7、用信号量实现互斥解决计算π的竞争条件。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
#include <math.h>
#include "timer.h"
int n,thread_count;
double sum=0.0;

sem_t sem1,sem2;

void* Thread_sum(void* rank){
    long my_rank=(long)rank;
    double factor,my_sum=0.0;
    long long i;
    long long my_n=n/thread_count;
    long long my_first_i=my_n*my_rank;
    long long my_last_i=my_first_i+my_n;

    if(my_first_i % 2==0 ){
        factor=1.0;
    }else{
        factor=-1.0;
    }
    for(i=my_first_i;i<my_last_i;i++,factor=-factor){
        my_sum+=factor/(2*i+1);
    }
    if(my_rank==0)
        sem_wait(&sem1);
    else
        sem_wait(&sem2);
    sum+=my_sum;
    if(my_rank == 0)
        sem_post(&sem2);
    else
        sem_post(&sem1);
    // pthread_exit(NULL);
    return NULL;
}
int main(int argc,char* argv[]){
    double start, finish, elapsed;
    long long i;
    //scanf("%d%d",&thread_count,&n);
    thread_count=atoi(argv[1]);
    n=atoi(argv[2]);
    //printf("%d\n%d\n",thread_count,n);
    //printf("%d\n%d\n%d\n",argc,argv[0],argv[1],argv[2]);
    printf("With n=%d terms\n",n);
    pthread_t thread_handles[thread_count];
    GET_TIME(start);
    sem_init(&sem1,0,1);
    sem_init(&sem2,0,0);
    for(i=0;i<thread_count;i++){
        pthread_create(&thread_handles[i],NULL,Thread_sum,(void *)i);
    }
    for(i=0;i<thread_count;i++){
        pthread_join(thread_handles[i],NULL);
    }
    sem_destroy(&sem1);
    sem_destroy(&sem2);
    GET_TIME(finish);
    printf("                   estimate of  pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time = %e seconds\n", elapsed);

    sum=0;
    GET_TIME(start);
    pthread_create(&thread_handles[0],NULL,Thread_sum,(void *)0);
    pthread_join(thread_handles[0],NULL);
    GET_TIME(finish);
    printf("    Single-threaded estimate of pi = %.15lf\n",4*sum);
    elapsed = finish - start;
    printf("    Elapsed time= %e seconds\n",elapsed);
    printf("    Math library estimate of    pi = %.15lf\n",4*atan(1.0));
    return 0;
}
image

8、修改信号量的初值，调换上述2中的线程顺序。

#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>

sem_t sem1,sem2;
void* fun(void* rank){
    int i;
    int my_rank=(int)rank;
    for(i=1;i<=5;i++){
      if(my_rank==0)
        sem_wait(&sem1);
      else
        sem_wait(&sem2);
        printf("Thread %d:%d\n",my_rank,i);
        sleep(1);
      if(my_rank==0)
        sem_post(&sem2);
      else
        sem_post(&sem1);
    }
    pthread_exit(0);
}
int main(){
  pthread_t tid1,tid2;  //the 2 thread identifier
  int num1=0,num2=1;

  sem_init(&sem1,0,1);
  sem_init(&sem2,0,0);
  //create the thread
  pthread_create(&tid1,NULL,fun,(void *)num1);
  pthread_create(&tid2,NULL,fun,(void *)num2);
  //now wait for the thread to exit
  pthread_join(tid1,NULL);
  pthread_join(tid2,NULL);

  sem_destroy(&sem1);
  sem_destroy(&sem2);
}
image

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