c program

Goal: Multithreaded sieve of eratosthenes

This program seems to crash when entering ./a.out -t 2 -u 10000 or even just using the default values ./a.out

typedef struct BitBlock {

uint32_t bits;

pthread_mutex_t mutex;

} BitBlock_t;

static uint32_t val = 10240;

static BitBlock_t b[4];

static int num_threads = 1;

static unsigned short isVerbose;

void setbit(BitBlock_t a[], uint32_t k) {

pthread_mutex_lock(&a[k / 32].mutex);

a[k / 32].bits |= 1 << (k % 32);

pthread_mutex_unlock(&a[k / 32].mutex);

}

void clearbit(BitBlock_t a[], uint32_t k) {

a[k / 32].bits &= ~(1 << (k % 32));

}

int testbit(BitBlock_t a[], uint32_t k) {

int test = -1;

pthread_mutex_lock(&a[k / 32].mutex);

test = ((a[k / 32].bits & (1 << (k % 32))) != 0);

pthread_mutex_unlock(&a[k / 32].mutex);

return test;

}

void* sieveoferatosthenes(void* vid) {

long tid = (long)vid;

uint32_t start = tid * (val / num_threads) + 2;

uint32_t end = (tid == num_threads - 1) ? val : start + (val / num_threads) - 1;

for (uint32_t j = start; j <= end; j++) {

for (uint32_t p = 2; p * p <= j; p++) {

if (testbit(b, p) != 1) {

for (uint32_t i = p * p; i <= j; i += p) {

setbit(b, i);

}

}

}

}

pthread_exit(EXIT_SUCCESS);

}

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

int opt = -1;

pthread_t* threads = NULL;

long tid = 0;

for (int i = 0; i < 4; i++) {

pthread_mutex_init(&b[i].mutex, NULL);

b[i].bits = 0;

}

while ((opt = getopt(argc, argv, "t:u:hv")) != -1) {

switch (opt) {

case 't':

num_threads = atoi(optarg);

break;

case 'u':

val = atoi(optarg);

break;

case 'h':

printf("%s: -t # -u # -h -v ", argv[0]);

printf("\t-t # for number of threads ");

printf("\t-u # for the upper bound of largest number "); exit(0); break; case 'v': isVerbose = 1; break; default: /* '?' */ exit(EXIT_FAILURE); break; }

}

threads = malloc(num_threads * sizeof(pthread_t)); if(isVerbose) { fprintf(stderr, "number of threads: %d", num_threads); fprintf(stderr, "upper bound: %d", val); }

for (tid = 0; tid < num_threads; tid++) { pthread_create(&threads[tid], NULL, sieveoferatosthenes, (void *) tid); }

for (tid = 0; tid < num_threads; tid++) { pthread_join(threads[tid], NULL); }

for (uint32_t p = 2; p <= val; p++) { if (testbit(b, p) != 1) printf("%u ", p); }

free(threads); for(int i = 0; i < 4; i++) { pthread_mutex_destroy(&b[i].mutex); }

return EXIT_SUCCESS; }