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背景信息： 我正在嘗試創建一個C程序，它允許我通過幾個不同的文件（源文件中的2個）搜索最大的素數。該程序是多線程的，以加快進程。在這個程序中，我更喜歡計算時間，而不是浪費時間，讓線程等待，直到所有線程都分配了globalLargestPrime。稍微複雜的線程同步
問題： 我相信在我的程序的某個地方，要麼id沒有被正確地作爲參數傳遞，要麼就是我的程序捱餓了其中一個線程。
奇怪的部分： 當我運行我的程序時，它將運行並完成，但有時它只會產生一個線程，因此它不會搜索兩個文本文件。而其他時候，將產生兩個線程，並從兩個文本文件
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <pthread.h>
#include <time.h>
pthread_mutex_t mutex;
pthread_cond_t monitor[2];
int globalLargestPrime = 0;
const int numThreads = 2;
FILE *fIN[2];
typedef enum{
FREE,
IN_USE
}lrgstPrm;
lrgstPrm monLargestPrime;//create struct
int timed(){
return time(NULL);
}
int ChkPrim(int n){
int i;
int isPrime = 0;
int root = sqrt(n);
for(i=2; i<root; i++){
if(n % i == 0)
isPrime = 1;
else
isPrime = 0;
}
return isPrime;
}
void *calc_sqrt(void *threadID){//Create Threads
int index, currentNum;
int localLargestPrime = 0;
int id = *(int *)threadID;
int thousandsOfTimes = 0;
//FILE *fIN = fopen("data.txt", "r");
//printf(PTHREAD_MUTEX_ERRORCHECK);
//Calculate some sqrts
while(!feof(fIN[id])){
for(index = 0; index < 1000; index++)
{//Check every thousand times
fscanf(fIN[id], "%d\n", ¤tNum);
if(currentNum>localLargestPrime)
if(ChkPrim(currentNum) == 1)
localLargestPrime = currentNum;
}
pthread_mutex_lock(&mutex);
thousandsOfTimes++;
while(monLargestPrime == IN_USE)
pthread_cond_wait(&monitor[id], &mutex);//wait untill mutex is unlocked
monLargestPrime = IN_USE;
//Critical Zone
printf("Entering Critical Zone My ID: %d\n",id);
if(localLargestPrime > globalLargestPrime)//Check for largest num
globalLargestPrime = localLargestPrime;
else
localLargestPrime = globalLargestPrime;
for(index = 0; index < numThreads; index++)
if(index != id)
pthread_cond_signal(&monitor[id]);//signal all threads that mutex is unlocked
monLargestPrime = FREE;
printf("Exiting Critical Zone My ID: %d\n",id);
pthread_mutex_unlock(&mutex);
// printf("done searching thousand times %d My ID: %d\n",thousandsOfTimes, id);
}
}
void createText(){
FILE *fOUT = fopen("data.txt", "w");
int i;
srand(time(NULL));
for(i=0; i<10000; i++)
fprintf(fOUT, "%d\n",rand()%5000);
fclose(fOUT);
}
int main(){
printf("This is before creating threads\n");
int index, timeDiff;
pthread_t threads[2];
pthread_mutex_init(&mutex, NULL);
for(index = 0; index < numThreads; index++)
pthread_cond_init(&monitor[index], NULL);
fIN[0] = fopen("data0.txt","r");
fIN[1] = fopen("data1.txt","r");
timeDiff = time(NULL);
//createText();
for(index = 0; index < numThreads; index++){
//int *id = malloc(1);
//*id = index;
pthread_create(&threads[index],NULL,calc_sqrt,&index);
}
for(index = 0; index < numThreads; index++)
pthread_join(threads[index],NULL);
printf("This is after creating threads");
timeDiff = timed() - timeDiff;
/*Destroy the mutexes & conditional signals*/
pthread_mutex_destroy(&mutex);
pthread_cond_destroy(&monitor[0]);
pthread_cond_destroy(&monitor[1]);
printf("This is the Time %d\n", timeDiff);
printf("This is the Largest Prime Number: %d", globalLargestPrime);
return 0;
}
閱讀如果有人能告訴我它可以理解這個問題的一些見解
感謝
謝謝，它的工作。我覺得這將是一個簡單的錯誤。非常感謝！ – Kevin