improve primes lib

This commit is contained in:
Dr. Matthias Ratajczak
2022-08-19 20:12:20 +02:00
parent 571b525843
commit 6fd36005fc
+11 -11
View File
@@ -26,18 +26,18 @@ where
assert!(min_value > 1);
assert!(max_value > min_value);
Self::from_array(
Self::get_prime_numbers_array(&min_value, &max_value),
&min_value,
&max_value,
&Self::get_prime_numbers_array(min_value, max_value),
min_value,
max_value,
)
}
fn from_array(array: Vec<bool>, min_value: &usize, max_value: &usize) -> Self {
fn from_array(array: &[bool], min_value: usize, max_value: usize) -> Self {
let number_of_primes = array.iter().filter(|b| **b).count();
let mut vector = Vec::with_capacity(number_of_primes);
let mut set = HashSet::with_capacity(number_of_primes);
for number in *min_value..*max_value {
for number in min_value..max_value {
let idx = number - min_value;
// SAFETY: see considerations in get_prime_numbers_array
if unsafe { *array.get_unchecked(idx) } {
@@ -51,16 +51,16 @@ where
Primes { vector, set }
}
fn get_prime_numbers_array(min_value: &usize, max_value: &usize) -> Vec<bool> {
fn get_prime_numbers_array(min_value: usize, max_value: usize) -> Vec<bool> {
// Sieve of Eratosthenes
let length = *max_value - *min_value;
let length = max_value - min_value;
let mut result = vec![true; length];
let upper_limit = Self::calc_upper_limit(max_value);
for i in 2..upper_limit {
let skip = Self::find_number_to_skip_until_min_value(min_value, i);
for multiple in (i * i..*max_value).step_by(i).skip(skip) {
for multiple in (i * i..max_value).step_by(i).skip(skip) {
let idx = multiple - min_value;
// SAFETY: `multiple` will always be between min_value and max_value
// (which define the length of the array), therfore idx is always smaller than the
@@ -72,11 +72,11 @@ where
result
}
fn calc_upper_limit(max_value: &usize) -> usize {
f64::sqrt(*max_value as f64).ceil() as usize
fn calc_upper_limit(max_value: usize) -> usize {
f64::sqrt(max_value as f64).ceil() as usize
}
fn find_number_to_skip_until_min_value(min_value: &usize, i: usize) -> usize {
fn find_number_to_skip_until_min_value(min_value: usize, i: usize) -> usize {
((min_value.saturating_sub(i * i)) as f64 / i as f64).ceil() as usize
}