cross threading - Page 27

Threading across multiple files

- by Zach M.

My program is reading in files and using thread to compute the highest prime number, when I put a print statement into the getNum() function my numbers are printing out. However, it seems to just lag no matter how many threads I input. Each file has 1 million integers in it. Does anyone see something apparently wrong with my code? Basically the code is giving each thread 1000 integers to check before assigning a new thread. I am still a C noobie and am just learning the ropes of threading. My code is a mess right now because I have been switching things around constantly. #include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> #include <pthread.h> #include <math.h> #include <semaphore.h> //Global variable declaration char *file1 = "primes1.txt"; char *file2 = "primes2.txt"; char *file3 = "primes3.txt"; char *file4 = "primes4.txt"; char *file5 = "primes5.txt"; char *file6 = "primes6.txt"; char *file7 = "primes7.txt"; char *file8 = "primes8.txt"; char *file9 = "primes9.txt"; char *file10 = "primes10.txt"; char **fn; //file name variable int numberOfThreads; int *highestPrime = NULL; int fileArrayNum = 0; int loop = 0; int currentFile = 0; sem_t semAccess; sem_t semAssign; int prime(int n)//check for prime number, return 1 for prime 0 for nonprime { int i; for(i = 2; i <= sqrt(n); i++) if(n % i == 0) return(0); return(1); } int getNum(FILE* file) { int number; char* tempS = malloc(20 *sizeof(char)); fgets(tempS, 20, file); tempS[strlen(tempS)-1] = '\0'; number = atoi(tempS); free(tempS);//free memory for later call return(number); } void* findPrimality(void *threadnum) //main thread function to find primes { int tNum = (int)threadnum; int checkNum; char *inUseFile = NULL; int x=1; FILE* file; while(currentFile < 10){ if(inUseFile == NULL){//inUseFIle being used to check if a file is still being read sem_wait(&semAccess);//critical section inUseFile = fn[currentFile]; sem_post(&semAssign); file = fopen(inUseFile, "r"); while(!feof(file)){ if(x % 1000 == 0 && tNum !=1){ //go for 1000 integers and then wait sem_wait(&semAssign); } checkNum = getNum(file); /* * * * * I think the issue is here * * * */ if(checkNum > highestPrime[tNum]){ if(prime(checkNum)){ highestPrime[tNum] = checkNum; } } x++; } fclose(file); inUseFile = NULL; } currentFile++; } } int main(int argc, char* argv[]) { if(argc != 2){ //checks for number of arguements being passed printf("To many ARGS\n"); return(-1); } else{//Sets thread cound to user input checking for correct number of threads numberOfThreads = atoi(argv[1]); if(numberOfThreads < 1 || numberOfThreads > 10){ printf("To many threads entered\n"); return(-1); } time_t preTime, postTime; //creating time variables int i; fn = malloc(10 * sizeof(char*)); //create file array and initialize fn[0] = file1; fn[1] = file2; fn[2] = file3; fn[3] = file4; fn[4] = file5; fn[5] = file6; fn[6] = file7; fn[7] = file8; fn[8] = file9; fn[9] = file10; sem_init(&semAccess, 0, 1); //initialize semaphores sem_init(&semAssign, 0, numberOfThreads); highestPrime = malloc(numberOfThreads * sizeof(int)); //create an array to store each threads highest number for(loop = 0; loop < numberOfThreads; loop++){//set initial values to 0 highestPrime[loop] = 0; } pthread_t calculationThread[numberOfThreads]; //thread to do the work preTime = time(NULL); //start the clock for(i = 0; i < numberOfThreads; i++){ pthread_create(&calculationThread[i], NULL, findPrimality, (void *)i); } for(i = 0; i < numberOfThreads; i++){ pthread_join(calculationThread[i], NULL); } for(i = 0; i < numberOfThreads; i++){ printf("this is a prime number: %d \n", highestPrime[i]); } postTime= time(NULL); printf("Wall time: %ld seconds\n", (long)(postTime - preTime)); } } Yes I am trying to find the highest number over all. So I have made some head way the last few hours, rescucturing the program as spudd said, currently I am getting a segmentation fault due to my use of structures, I am trying to save the largest individual primes in the struct while giving them the right indices. This is the revised code. So in short what the first thread is doing is creating all the threads and giving them access points to a very large integer array which they will go through and find prime numbers, I want to implement semaphores around the while loop so that while they are executing every 2000 lines or the end they update a global prime number. #include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> #include <pthread.h> #include <math.h> #include <semaphore.h> //Global variable declaration char *file1 = "primes1.txt"; char *file2 = "primes2.txt"; char *file3 = "primes3.txt"; char *file4 = "primes4.txt"; char *file5 = "primes5.txt"; char *file6 = "primes6.txt"; char *file7 = "primes7.txt"; char *file8 = "primes8.txt"; char *file9 = "primes9.txt"; char *file10 = "primes10.txt"; int numberOfThreads; int entries[10000000]; int entryIndex = 0; int fileCount = 0; char** fileName; int largestPrimeNumber = 0; //Register functions int prime(int n); int getNum(FILE* file); void* findPrimality(void *threadNum); void* assign(void *num); typedef struct package{ int largestPrime; int startingIndex; int numberCount; }pack; //Beging main code block int main(int argc, char* argv[]) { if(argc != 2){ //checks for number of arguements being passed printf("To many threads!!\n"); return(-1); } else{ //Sets thread cound to user input checking for correct number of threads numberOfThreads = atoi(argv[1]); if(numberOfThreads < 1 || numberOfThreads > 10){ printf("To many threads entered\n"); return(-1); } int threadPointer[numberOfThreads]; //Pointer array to point to entries time_t preTime, postTime; //creating time variables int i; fileName = malloc(10 * sizeof(char*)); //create file array and initialize fileName[0] = file1; fileName[1] = file2; fileName[2] = file3; fileName[3] = file4; fileName[4] = file5; fileName[5] = file6; fileName[6] = file7; fileName[7] = file8; fileName[8] = file9; fileName[9] = file10; FILE* filereader; int currentNum; for(i = 0; i < 10; i++){ filereader = fopen(fileName[i], "r"); while(!feof(filereader)){ char* tempString = malloc(20 *sizeof(char)); fgets(tempString, 20, filereader); tempString[strlen(tempString)-1] = '\0'; entries[entryIndex] = atoi(tempString); entryIndex++; free(tempString); } } //sem_init(&semAccess, 0, 1); //initialize semaphores //sem_init(&semAssign, 0, numberOfThreads); time_t tPre, tPost; pthread_t coordinate; tPre = time(NULL); pthread_create(&coordinate, NULL, assign, (void**)numberOfThreads); pthread_join(coordinate, NULL); tPost = time(NULL); } } void* findPrime(void* pack_array) { pack* currentPack= pack_array; int lp = currentPack->largestPrime; int si = currentPack->startingIndex; int nc = currentPack->numberCount; int i; int j = 0; for(i = si; i < nc; i++){ while(j < 2000 || i == (nc-1)){ if(prime(entries[i])){ if(entries[i] > lp) lp = entries[i]; } j++; } } return (void*)currentPack; } void* assign(void* num) { int y = (int)num; int i; int count = 10000000/y; int finalCount = count + (10000000%y); int sIndex = 0; pack pack_array[(int)num]; pthread_t workers[numberOfThreads]; //thread to do the workers for(i = 0; i < y; i++){ if(i == (y-1)){ pack_array[i].largestPrime = 0; pack_array[i].startingIndex = sIndex; pack_array[i].numberCount = finalCount; } pack_array[i].largestPrime = 0; pack_array[i].startingIndex = sIndex; pack_array[i].numberCount = count; pthread_create(&workers[i], NULL, findPrime, (void *)&pack_array[i]); sIndex += count; } for(i = 0; i< y; i++) pthread_join(workers[i], NULL); } //Functions int prime(int n)//check for prime number, return 1 for prime 0 for nonprime { int i; for(i = 2; i <= sqrt(n); i++) if(n % i == 0) return(0); return(1); }

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