size_t
distances_gcd(const Distances &distances)
{
if (distances.size() == 0) return 0;
if (distances.size() == 1) return distances[0];
size_t prev = binary_gcd(distances[0], distances[1]);
for (size_t x = 2; x < distances.size(); x++)
prev = binary_gcd(prev, distances[x]);
return prev;
}
long gcd(long *arr, int size) {
pthread_t threads[THREADS];
long id;
long res;
int status;
n = size;
a = (long*) malloc(size * sizeof(long));
memcpy(a, arr, size * sizeof(long));
for (id = 0; id < THREADS; id++) {
status = pthread_create(&threads[id], NULL, gcd_worker, (void*) id);
if (status) {
fprintf(stderr, "error %d in pthread_create\n", status);
}
}
for (id = 0; id < THREADS; id++) {
pthread_join(threads[id], NULL);
}
res = a[0];
for (id = 1; id < THREADS; id++) {
res = binary_gcd(res, a[id * n / THREADS]);
}
free(a);
return res;
}
long binary_gcd(long larger, long smaller) {
if (larger < smaller) {
// swap
larger ^= smaller;
smaller ^= larger;
larger ^= smaller;
}
if (smaller == 0) {
return larger;
}
return binary_gcd(smaller, larger % smaller);
}
void *gcd_worker(void *thread_id) {
long id;
int i;
int start;
int end;
id = (long) thread_id;
start = id * n/THREADS;
end = (id + 1) * n/THREADS;
if (end > n) {
end = n;
}
for (i = start; i < end; i++) {
a[start] = binary_gcd(a[start], a[i]);
}
return NULL;
}
int main()
{
std::cout << binary_gcd(1517, 1739) << std::endl;
return 0;
}
