Add dichotomic search to utils

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Louis Dureuil 2023-02-15 12:29:36 +01:00
parent 1db7d5d851
commit f1119f2dc2
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@ -538,3 +538,37 @@ impl IndexScheduler {
} }
} }
} }
pub fn dichotomic_search(start_point: usize, mut is_good: impl FnMut(usize) -> bool) -> usize {
let mut biggest_good = None;
let mut smallest_bad = None;
let mut current = start_point;
loop {
let is_good = is_good(current);
(biggest_good, smallest_bad, current) = match (biggest_good, smallest_bad, is_good) {
(None, None, false) => (None, Some(current), current / 2),
(None, None, true) => (Some(current), None, current * 2),
(None, Some(smallest_bad), true) => {
(Some(current), Some(smallest_bad), (current + smallest_bad) / 2)
}
(None, Some(_), false) => (None, Some(current), current / 2),
(Some(_), None, true) => (Some(current), None, current * 2),
(Some(biggest_good), None, false) => {
(Some(biggest_good), Some(current), (biggest_good + current) / 2)
}
(Some(_), Some(smallest_bad), true) => {
(Some(current), Some(smallest_bad), (smallest_bad + current) / 2)
}
(Some(biggest_good), Some(_), false) => {
(Some(biggest_good), Some(current), (biggest_good + current) / 2)
}
};
if current == 0 {
return current;
}
if smallest_bad.is_some() && biggest_good.is_some() && biggest_good >= Some(current) {
return current;
}
}
}