pai1.c

采用Pthread+C++方式进行多线程求Pai

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#include<math.h>
#include<time.h>
int N=10000000;
int M=0;
double pai=0;
double THREAD_NUMBER=2;
static pthread_mutex_t mutex=PTHREAD_MUTEX_INITIALIZER;// quick lock
void* calculatePai(void *arg){

 int i;
 int thread_id=*(int*)arg;
 double tmp;
 for(i=thread_id;i<N;i+=THREAD_NUMBER){
  tmp=4.0/(1+((i+0.5)/N*(i+0.5)/N));
  
  pthread_mutex_lock(&mutex);
   pai+=tmp;
  pthread_mutex_unlock(&mutex);
 }
}
void* MonteKarlo(void *arg ){
  
  
  int i;
  int thread_id=*(int*)arg;
  for(i=thread_id;i<N;i+=THREAD_NUMBER)
  {
  double x=(double)((rand()%11));
  double y=(double)((rand()%11));
  double dis=x*x+y*y;
  if(dis<=100){
  pthread_mutex_lock(&mutex); 
   M++;
  pthread_mutex_unlock(&mutex);
  }
 }
}

int main(int argc,char* argv[]){

  int m,n;
  
  if(argc<3){
    printf("Number of arguments must be greate than 2!\n");
    exit(1);
   }
   m=atoi(argv[1]);
   n=atoi(argv[2]);
   if(m<0||n<0){
    printf("arguments must be >0!\n");
    exit(1);
   }
  THREAD_NUMBER=m;
  N=n;
  
  //printf("argc=%d m=%d n=%d\n",argc,m,n);  
  pthread_t pt[50];
  int i;
  int arg[50];
  time_t begin_time,end_time;
  clock_t start,finish;

  begin_time=time(NULL);
  start=clock();
 for(i=0;i<THREAD_NUMBER;i++){
   arg[i]=i;
 /* if(pthread_create(&pt[i],NULL,MonteKarlo,(void*)&arg[i])){
    printf("pthread_create error\n");
      exit(1);
   }*/
  
 if(pthread_create(&pt[i],NULL,calculatePai,(void*)&arg[i])){
    printf("pthread_create error\n");
      exit(1);
   }
  
  }
 
 for(i=0;i<THREAD_NUMBER;i++){
  if(pthread_join(pt[i],NULL)){
    printf("pthread_join error\n");
     exit(1);
  }
 }
 pai/=N;
 //printf("pai=%lf\n",pai);
 finish=clock();
 end_time=time(NULL);

  //printf("Pai=%.5lf, time consumed:%lf\n",1.0*M/N*4,difftime(end_time,begin_time)); 
  //printf("Pai=%.5lf, time consumed:%lf\n",pai,difftime(end_time,begin_time)); 
  printf("Pai=%.5lf, time consumed:%lf\n",pai,(double)(finish-start)/CLOCKS_PER_SEC); 
  pthread_mutex_destroy(&mutex);

}