nortega/indivisible-legacy
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Don't test for divisibility by 2.

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We skip all even numbers, so we can skip 2, this also means giving 3 as
a given.
This commit is contained in:
Nicolás A. Ortega 2016-12-30 17:57:28 +01:00
parent 3e902efd18
commit f8726497a4
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GPG Key ID: 614272579C2070D1
1 changed files with 12 additions and 7 deletions
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19
src/main.c
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@ -116,12 +116,16 @@ int main(int argc, char *argv[]) {
fprintf(stderr, "Failed to allocate more memory for list.\n"); fprintf(stderr, "Failed to allocate more memory for list.\n");
goto releaseMemory; goto releaseMemory;
} }
if(!f_quiet) { // Add 3 as well to optimize the algorithm
if(mpz_out_str(stdout, base, num) == 0) mpz_set_ui(num, 3);
fprintf(stderr, "Could not print to `stdout'!\n"); if(addToList(&primes, num) == 1) {
printf("\n"); fprintf(stderr, "Failed to allocate more memory for list.\n");
goto releaseMemory;
} }
mpz_add_ui(num, num, 1); if(!f_quiet) {
puts("2\n3");
}
mpz_add_ui(num, num, 2);
} else { } else {
// Load primes from file // Load primes from file
int err = inputPrimes(file, &primes); int err = inputPrimes(file, &primes);
@ -167,9 +171,10 @@ int main(int argc, char *argv[]) {
mpz_fdiv_q_ui(halfNum, num, 2); mpz_fdiv_q_ui(halfNum, num, 2);
/** /**
* Loop through primes we've found until we get to half of the number * Loop through primes we've found until we get to half of the number
* we're analyzing * we're analyzing. Also, skip `2' since we're not testing even
* numbers.
*/ */
for(size_t i = 0; mpz_cmp(primes.list[i], halfNum) < 0; ++i) { for(size_t i = 1; mpz_cmp(primes.list[i], halfNum) < 0; ++i) {
// 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 nextNum; goto nextNum;