nortega/indivisible-legacy
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Optimize the algorithm to avoid numbers larger than half.

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Nicolás A. Ortega 2016-12-10 14:46:51 +01:00
parent 8a42e85d04
commit f4ee9872bc
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GPG Key ID: 614272579C2070D1
1 changed files with 12 additions and 2 deletions
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14
src/main.c
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@ -36,9 +36,17 @@ int main(void) {
printf("\n"); printf("\n");
mpz_add_ui(num, num, 1); mpz_add_ui(num, num, 1);
// Variable for half `num'
mpz_t halfNum;
mpz_init(halfNum);
do { do {
// Calculate half of `num'
mpz_fdiv_q_ui(halfNum, num, 2);
// Loop through found primes // Loop through found primes
for(ulli i = 0; i < primes.size; ++i) { for(ulli i = 0; i < primes.size; ++i) {
// If the prime we're looking at is >= half of `num' then we can skip the rest
if(mpz_cmp(primes.list[i], halfNum) >= 0) break;
// If `num' is divisible by a prime then go to the next number // If `num' is divisible by a prime then go to the next number
if(mpz_divisible_p(num, primes.list[i]) != 0) if(mpz_divisible_p(num, primes.list[i]) != 0)
goto nextPrime; goto nextPrime;
@ -46,7 +54,7 @@ int main(void) {
// `num' is a prime so we add it to the list and print it // `num' is a prime so we add it to the list and print it
addToList(&primes, num); addToList(&primes, num);
if(unlikely(mpz_out_str(stdout, 10, num) == 0)) { if(mpz_out_str(stdout, 10, num) == 0) {
fprintf(stderr, "Could not print to `stdout'!\n"); fprintf(stderr, "Could not print to `stdout'!\n");
exit(1); exit(1);
} }
@ -55,8 +63,10 @@ int main(void) {
nextPrime: nextPrime:
// Add 2 (skip even numbers since they're all divisible by 2) // Add 2 (skip even numbers since they're all divisible by 2)
mpz_add_ui(num, num, 2); mpz_add_ui(num, num, 2);
} while(likely(run)); } while(run);
// Clear GMP variables
mpz_clear(halfNum);
mpz_clear(num); mpz_clear(num);
// Deinitialize the list // Deinitialize the list
deInitList(&primes); deInitList(&primes);