c - 线程编程...终端无输出

Question

我正在进行线程编程并尝试实现蒙特卡罗技术来计算其中的 Pi 值。我编译了代码并且没有错误，但是当我执行时我没有得到任何输出。如有错误请指正。

这是我的代码:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>

#define frand() ((double) rand() / (RAND_MAX))
#define MAX_LEN 1353
const size_t N = 4;
float circlePoints=0;
void* point_counter(void *param){
    float xcord; 
    float ycord; 
    while(MAX_LEN){

        xcord=frand();
        ycord=frand();
        float cord = (xcord*xcord) + (ycord*ycord);

        if(cord <= 1){
            circlePoints++;}
    }
}

int main()
{
    printf("out");
    size_t i;
    pthread_t thread[N];

    srand(time(NULL));
    for( i=0;i <4;++i){
        printf("in creating thread");
        pthread_create( &thread[i], NULL, &point_counter, NULL);
    }
    for(i=0;i <4;++i){
        printf("in joining thread");
        pthread_join( thread[i], NULL );
    }
    for( i=0;i <4;++i){
        printf("in last thread");
        float pi = 4.0 * (float)circlePoints /MAX_LEN;

        printf("pi is %2.4f: \n", pi);
    }
    return 0;
}

Answer 1

您在这里遇到了无限循环:

while(MAX_LEN){

因为 MAX_LEN 一直都是非零。

至于为什么在此之前没有看到任何输出，请参阅 Why does printf not flush after the call unless a newline is in the format string?