big first commit

taiko/src/difficulty_object.rs

@@ -0,0 +1,34 @@
+use super::{closest_rhythm, HitObjectRhythm};
+
+use parse::HitObject;
+
+#[derive(Clone, Debug)]
+pub(crate) struct DifficultyObject<'o> {
+    pub(crate) idx: usize,
+    pub(crate) base: &'o HitObject,
+    pub(crate) prev: &'o HitObject,
+    pub(crate) delta: f32,
+    pub(crate) rhythm: &'static HitObjectRhythm,
+}
+
+impl<'o> DifficultyObject<'o> {
+    #[inline]
+    pub(crate) fn new(
+        idx: usize,
+        base: &'o HitObject,
+        prev: &'o HitObject,
+        prev_prev: &HitObject,
+        clock_rate: f32,
+    ) -> Self {
+        let delta = (base.start_time - prev.start_time) / clock_rate;
+        let rhythm = closest_rhythm(delta, prev, prev_prev, clock_rate);
+
+        Self {
+            idx,
+            base,
+            prev,
+            delta,
+            rhythm,
+        }
+    }
+}

taiko/src/hitobject_rhythm.rs

@@ -0,0 +1,65 @@
+use parse::HitObject;
+use std::cmp::Ordering;
+
+lazy_static::lazy_static! {
+    /// lazy_static required for `f32` division's
+    /// lack of const-ness as of now.
+    static ref COMMON_RHYTHMS: Vec<HitObjectRhythm> = vec![
+        HitObjectRhythm::new(1.0, 1.0, 0.0),
+        HitObjectRhythm::new(2.0, 1.0, 0.3),
+        HitObjectRhythm::new(1.0, 2.0, 0.5),
+        HitObjectRhythm::new(3.0, 1.0, 0.3),
+        HitObjectRhythm::new(1.0, 3.0, 0.35),
+        HitObjectRhythm::new(3.0, 2.0, 0.6),
+        HitObjectRhythm::new(2.0, 3.0, 0.4),
+        HitObjectRhythm::new(5.0, 4.0, 0.5),
+        HitObjectRhythm::new(4.0, 5.0, 0.7),
+    ];
+}
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct HitObjectRhythm {
+    ratio: f32,
+    pub(crate) difficulty: f32,
+}
+
+impl PartialEq for HitObjectRhythm {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        (self.ratio - other.ratio).abs() < f32::EPSILON
+            && (self.difficulty - other.difficulty).abs() < f32::EPSILON
+    }
+}
+
+impl Eq for HitObjectRhythm {}
+
+impl HitObjectRhythm {
+    #[inline]
+    fn new(numerator: f32, denominator: f32, difficulty: f32) -> Self {
+        Self {
+            ratio: numerator / denominator,
+            difficulty,
+        }
+    }
+}
+
+#[inline]
+pub(crate) fn closest_rhythm(
+    delta_time: f32,
+    last: &HitObject,
+    last_last: &HitObject,
+    clock_rate: f32,
+) -> &'static HitObjectRhythm {
+    let prev_len = (last.start_time - last_last.start_time) / clock_rate;
+    let ratio = delta_time / prev_len;
+
+    COMMON_RHYTHMS
+        .iter()
+        .min_by(|r1, r2| {
+            (r1.ratio - ratio)
+                .abs()
+                .partial_cmp(&(r2.ratio - ratio).abs())
+                .unwrap_or(Ordering::Equal)
+        })
+        .unwrap()
+}

taiko/src/lib.rs

@@ -0,0 +1,225 @@
+mod difficulty_object;
+mod hitobject_rhythm;
+mod limited_queue;
+mod rim;
+mod skill;
+mod skill_kind;
+mod stamina_cheese;
+
+use difficulty_object::DifficultyObject;
+use hitobject_rhythm::{closest_rhythm, HitObjectRhythm};
+use limited_queue::LimitedQueue;
+use rim::Rim;
+use skill::Skill;
+use skill_kind::SkillKind;
+use stamina_cheese::StaminaCheeseDetector;
+
+use parse::{Beatmap, Mods};
+
+use std::cmp::Ordering;
+use std::f32::consts::PI;
+
+const SECTION_LEN: f32 = 400.0;
+
+const COLOR_SKILL_MULTIPLIER: f32 = 0.01;
+const RHYTHM_SKILL_MULTIPLIER: f32 = 0.014;
+const STAMINA_SKILL_MULTIPLIER: f32 = 0.02;
+
+/// Star calculation for osu!taiko maps
+pub fn stars(map: &Beatmap, mods: impl Mods) -> f32 {
+    if map.hit_objects.len() < 2 {
+        return 0.0;
+    }
+
+    // True if the object at that index is stamina cheese
+    let cheese = map.find_cheese();
+
+    let mut skills = vec![
+        Skill::new(SkillKind::color()),
+        Skill::new(SkillKind::rhythm()),
+        Skill::new(SkillKind::stamina(true)),
+        Skill::new(SkillKind::stamina(false)),
+    ];
+
+    let clock_rate = mods.speed();
+    let section_len = SECTION_LEN * clock_rate;
+
+    // No strain for first object
+    let mut current_section_end =
+        (map.hit_objects[0].start_time / section_len).ceil() * section_len;
+
+    let hit_objects = map
+        .hit_objects
+        .iter()
+        .enumerate()
+        .skip(2)
+        .zip(map.hit_objects.iter().skip(1))
+        .zip(map.hit_objects.iter())
+        .map(|(((idx, base), prev), prev_prev)| {
+            DifficultyObject::new(idx, base, prev, prev_prev, clock_rate)
+        });
+
+    for h in hit_objects {
+        while h.base.start_time > current_section_end {
+            for skill in skills.iter_mut() {
+                skill.save_current_peak();
+                skill.start_new_section_from(current_section_end);
+            }
+
+            current_section_end += section_len;
+        }
+
+        for skill in skills.iter_mut().take(3) {
+            skill.process(h.clone(), &cheese);
+        }
+
+        skills[3].process(h, &cheese);
+    }
+
+    for skill in skills.iter_mut() {
+        skill.save_current_peak();
+    }
+
+    let mut buf = vec![0.0; skills[0].strain_peaks.len()];
+
+    let color_rating = skills[0].difficulty_value(&mut buf) * COLOR_SKILL_MULTIPLIER;
+    let rhythm_rating = skills[1].difficulty_value(&mut buf) * RHYTHM_SKILL_MULTIPLIER;
+
+    let mut stamina_rating = (skills[2].difficulty_value(&mut buf)
+        + skills[3].difficulty_value(&mut buf))
+        * STAMINA_SKILL_MULTIPLIER;
+
+    let stamina_penalty = simple_color_penalty(stamina_rating, color_rating);
+    stamina_rating *= stamina_penalty;
+
+    let combined_rating = locally_combined_difficulty(&skills, stamina_penalty);
+    let separate_rating = norm(1.5, color_rating, rhythm_rating, stamina_rating);
+
+    rescale(1.4 * separate_rating + 0.5 * combined_rating)
+}
+
+#[inline]
+fn rescale(stars: f32) -> f32 {
+    if stars < 0.0 {
+        stars
+    } else {
+        10.43 * (stars / 8.0 + 1.0).ln()
+    }
+}
+
+#[inline]
+fn simple_color_penalty(stamina: f32, color: f32) -> f32 {
+    if color <= 0.0 {
+        0.79 - 0.25
+    } else {
+        0.79 - (stamina / color - 12.0).atan() / PI / 2.0
+    }
+}
+
+fn locally_combined_difficulty(skills: &[Skill], stamina_penalty: f32) -> f32 {
+    let mut peaks = Vec::with_capacity(skills[0].strain_peaks.len());
+
+    let iter = skills[0]
+        .strain_peaks
+        .iter()
+        .zip(skills[1].strain_peaks.iter())
+        .zip(skills[2].strain_peaks.iter())
+        .zip(skills[3].strain_peaks.iter())
+        .map(|(((&color, &rhythm), &stamina_right), &stamina_left)| {
+            norm(
+                2.0,
+                color * COLOR_SKILL_MULTIPLIER,
+                rhythm * RHYTHM_SKILL_MULTIPLIER,
+                (stamina_right + stamina_left) * STAMINA_SKILL_MULTIPLIER * stamina_penalty,
+            )
+        });
+
+    peaks.extend(iter);
+    peaks.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
+
+    let mut difficulty = 0.0;
+    let mut weight = 1.0;
+
+    for strain in peaks {
+        difficulty += strain * weight;
+        weight *= 0.9;
+    }
+
+    difficulty
+}
+
+#[inline]
+fn norm(p: f32, a: f32, b: f32, c: f32) -> f32 {
+    (a.powf(p) + b.powf(p) + c.powf(p)).powf(p.recip())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::File;
+
+    #[test]
+    fn test_single() {
+        let file = match File::open("E:/Games/osu!/beatmaps/1097541.osu") {
+            Ok(file) => file,
+            Err(why) => panic!("Could not open file: {}", why),
+        };
+
+        let map = match Beatmap::parse(file) {
+            Ok(map) => map,
+            Err(why) => panic!("Error while parsing map: {}", why),
+        };
+
+        let stars = stars(&map, 16);
+
+        println!("Stars: {}", stars);
+    }
+
+    #[test]
+    fn test_taiko() {
+        let margin = 0.005;
+
+        #[rustfmt::skip]
+        let data = vec![
+            (110219, 1 << 8, 4.090461690284154),  // HT
+            (110219, 0, 5.137432251440863),       // NM
+            (110219, 1 << 6, 6.785308286298745),  // DT
+
+            (168450, 1 << 8, 3.9102755155437663), // HT
+            (168450, 0, 4.740171803038067),       // NM
+            (168450, 1 << 6, 5.894260068145283),  // DT
+
+            (1097541, 1 << 8, 4.0027499635116595),// HT
+            (1097541, 0, 4.891409786886079),      // NM
+            (1097541, 1 << 6, 6.587467490088248), // DT
+
+            (1432878, 1 << 8, 3.5850143199594258),// HT
+            (1432878, 0, 4.416206873466799),      // NM
+            (1432878, 1 << 6, 5.908970879987477), // DT
+        ];
+
+        for (map_id, mods, expected_stars) in data {
+            let file = match File::open(format!("./test/{}.osu", map_id)) {
+                Ok(file) => file,
+                Err(why) => panic!("Could not open file {}.osu: {}", map_id, why),
+            };
+
+            let map = match Beatmap::parse(file) {
+                Ok(map) => map,
+                Err(why) => panic!("Error while parsing map {}: {}", map_id, why),
+            };
+
+            let stars = stars(&map, mods);
+
+            assert!(
+                (stars - expected_stars).abs() < margin,
+                "Stars: {} | Expected: {} => {} margin [map {} | mods {}]",
+                stars,
+                expected_stars,
+                (stars - expected_stars).abs(),
+                map_id,
+                mods
+            );
+        }
+    }
+}

taiko/src/limited_queue.rs

@@ -0,0 +1,83 @@
+use std::cmp::Ordering;
+use std::ops::Index;
+
+pub(crate) struct LimitedQueue<T> {
+    queue: Vec<T>,
+    start: usize,
+    end: usize,
+}
+
+impl<T> LimitedQueue<T> {
+    /// Panics if `capacity` is zero.
+    #[inline]
+    pub(crate) fn new(capacity: usize) -> Self {
+        Self {
+            end: capacity - 1,
+            start: 0,
+            queue: Vec::with_capacity(capacity),
+        }
+    }
+
+    #[inline]
+    pub(crate) fn push(&mut self, elem: T) {
+        let capacity = self.queue.capacity();
+        self.end = (self.end + 1) % capacity;
+
+        if self.queue.len() == capacity {
+            self.start = (self.start + 1) % capacity;
+            self.queue[self.end as usize] = elem;
+        } else {
+            self.queue.push(elem);
+        }
+    }
+
+    #[inline]
+    pub(crate) fn len(&self) -> usize {
+        self.queue.len()
+    }
+
+    #[inline]
+    pub(crate) fn last(&self) -> Option<&T> {
+        self.queue.get(self.end as usize)
+    }
+
+    #[inline]
+    pub(crate) fn clear(&mut self) {
+        self.start = 0;
+        self.end = self.queue.capacity() - 1;
+        self.queue.clear();
+    }
+
+    #[inline]
+    pub(crate) fn full(&self) -> bool {
+        self.queue.len() == self.queue.capacity()
+    }
+}
+
+impl<T: PartialOrd> LimitedQueue<T> {
+    pub(crate) fn min(&self) -> Option<&T> {
+        let mut iter = self.queue.iter();
+
+        if let Some(first) = iter.next() {
+            let min = iter.fold(first, |min, next| match min.partial_cmp(next) {
+                Some(Ordering::Less) => min,
+                Some(Ordering::Equal) => min,
+                Some(Ordering::Greater) => next,
+                None => min,
+            });
+
+            Some(min)
+        } else {
+            None
+        }
+    }
+}
+
+impl<T> Index<usize> for LimitedQueue<T> {
+    type Output = T;
+
+    #[inline]
+    fn index(&self, idx: usize) -> &Self::Output {
+        &self.queue[(self.start + idx) % self.queue.capacity()]
+    }
+}

taiko/src/rim.rs

@@ -0,0 +1,19 @@
+use parse::{HitObject, HitSound};
+
+pub(crate) trait Rim {
+    fn is_rim(&self) -> bool;
+}
+
+impl Rim for HitObject {
+    #[inline]
+    fn is_rim(&self) -> bool {
+        self.sound.clap() || self.sound.whistle()
+    }
+}
+
+impl Rim for u8 {
+    #[inline]
+    fn is_rim(&self) -> bool {
+        self.clap() || self.whistle()
+    }
+}

taiko/src/skill.rs

@@ -0,0 +1,97 @@
+use super::{DifficultyObject, SkillKind};
+
+use std::cmp::Ordering;
+
+const DECAY_WEIGHT: f32 = 0.9;
+
+pub(crate) struct Skill<'o> {
+    pub current_strain: f32,
+    current_section_peak: f32,
+
+    kind: SkillKind<'o>,
+    pub(crate) strain_peaks: Vec<f32>,
+
+    prev_time: Option<f32>,
+}
+
+impl<'o> Skill<'o> {
+    #[inline]
+    pub(crate) fn new(kind: SkillKind<'o>) -> Self {
+        Self {
+            current_strain: 1.0,
+            current_section_peak: 1.0,
+
+            kind,
+            strain_peaks: Vec::with_capacity(128),
+
+            prev_time: None,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn save_current_peak(&mut self) {
+        if self.prev_time.is_some() {
+            self.strain_peaks.push(self.current_section_peak);
+        }
+    }
+
+    #[inline]
+    pub(crate) fn start_new_section_from(&mut self, time: f32) {
+        if let Some(prev) = self.prev_time {
+            self.current_section_peak = self.peak_strain(time - prev);
+        }
+    }
+
+    #[inline]
+    pub(crate) fn process(&mut self, current: DifficultyObject<'o>, cheese: &[bool]) {
+        self.current_strain *= self.strain_decay(current.delta);
+        self.current_strain +=
+            self.kind.strain_value_of(&current, cheese) * self.skill_multiplier();
+        self.current_section_peak = self.current_section_peak.max(self.current_strain);
+        self.prev_time.replace(current.base.start_time);
+    }
+
+    #[inline]
+    pub(crate) fn difficulty_value(&self, buf: &mut [f32]) -> f32 {
+        let mut difficulty = 0.0;
+        let mut weight = 1.0;
+
+        buf.copy_from_slice(&self.strain_peaks);
+        buf.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
+
+        for &strain in buf.iter() {
+            difficulty += strain * weight;
+            weight *= DECAY_WEIGHT;
+        }
+
+        difficulty
+    }
+
+    #[inline]
+    fn skill_multiplier(&self) -> f32 {
+        match self.kind {
+            SkillKind::Color { .. } => 1.0,
+            SkillKind::Rhythm { .. } => 10.0,
+            SkillKind::Stamina { .. } => 1.0,
+        }
+    }
+
+    #[inline]
+    fn strain_decay_base(&self) -> f32 {
+        match self.kind {
+            SkillKind::Color { .. } => 0.4,
+            SkillKind::Rhythm { .. } => 0.0,
+            SkillKind::Stamina { .. } => 0.4,
+        }
+    }
+
+    #[inline]
+    fn peak_strain(&self, delta_time: f32) -> f32 {
+        self.current_strain * self.strain_decay(delta_time)
+    }
+
+    #[inline]
+    fn strain_decay(&self, ms: f32) -> f32 {
+        self.strain_decay_base().powf(ms / 1000.0)
+    }
+}

taiko/src/skill_kind.rs

@@ -0,0 +1,285 @@
+use super::{DifficultyObject, LimitedQueue, Rim};
+
+const RHYTHM_STRAIN_DECAY: f32 = 0.96;
+const MOST_RECENT_PATTERNS_TO_COMPARE: usize = 2;
+
+const MONO_HISTORY_MAX_LEN: usize = 5;
+const RHYTHM_HISTORY_MAX_LEN: usize = 8;
+const STAMINA_HISTORY_MAX_LEN: usize = 2;
+
+pub(crate) enum SkillKind<'o> {
+    Color {
+        mono_history: LimitedQueue<usize>,
+        prev_is_rim: Option<bool>,
+        current_mono_len: usize,
+    },
+    Rhythm {
+        rhythm_history: LimitedQueue<DifficultyObject<'o>>,
+        notes_since_rhythm_change: usize,
+        current_strain: f32,
+    },
+    Stamina {
+        note_pair_duration_history: LimitedQueue<f32>,
+        hand: u8,
+        off_hand_object_duration: f32,
+    },
+}
+
+impl<'o> SkillKind<'o> {
+    #[inline]
+    pub(crate) fn color() -> Self {
+        Self::Color {
+            mono_history: LimitedQueue::new(MONO_HISTORY_MAX_LEN),
+            prev_is_rim: None,
+            current_mono_len: 0,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn rhythm() -> Self {
+        Self::Rhythm {
+            rhythm_history: LimitedQueue::new(RHYTHM_HISTORY_MAX_LEN),
+            notes_since_rhythm_change: 0,
+            current_strain: 0.0,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn stamina(right_hand: bool) -> Self {
+        Self::Stamina {
+            note_pair_duration_history: LimitedQueue::new(STAMINA_HISTORY_MAX_LEN),
+            hand: right_hand as u8,
+            off_hand_object_duration: f32::MAX,
+        }
+    }
+
+    pub(crate) fn strain_value_of(
+        &mut self,
+        current: &DifficultyObject<'o>,
+        cheese: &[bool],
+    ) -> f32 {
+        match self {
+            Self::Color {
+                mono_history,
+                prev_is_rim,
+                current_mono_len,
+            } => {
+                let prev_is_circle = current.prev.is_circle();
+                let base_is_circle = current.base.is_circle();
+                let curr_is_rim = current.base.is_rim();
+
+                if !(current.delta < 1000.0 && prev_is_circle && base_is_circle) {
+                    mono_history.clear();
+                    *current_mono_len = base_is_circle as usize;
+
+                    *prev_is_rim = if base_is_circle {
+                        Some(curr_is_rim)
+                    } else {
+                        None
+                    };
+
+                    return 0.0;
+                }
+
+                let mut strain = 0.0;
+
+                if prev_is_rim
+                    .filter(|&is_rim| is_rim != curr_is_rim)
+                    .is_some()
+                {
+                    strain = if mono_history.len() < 2
+                        || (*mono_history.last().unwrap() + *current_mono_len) % 2 == 0
+                    {
+                        0.0
+                    } else {
+                        1.0
+                    };
+
+                    let mut reps_penalty = 1.0;
+
+                    mono_history.push(*current_mono_len);
+
+                    let iter = (0..mono_history
+                        .len()
+                        .saturating_sub(MOST_RECENT_PATTERNS_TO_COMPARE))
+                        .rev();
+
+                    for start in iter {
+                        let different_pattern = (0..MOST_RECENT_PATTERNS_TO_COMPARE).any(|i| {
+                            mono_history[start + i]
+                                != mono_history
+                                    [mono_history.len() + i - MOST_RECENT_PATTERNS_TO_COMPARE]
+                        });
+
+                        if different_pattern {
+                            continue;
+                        }
+
+                        let mut notes_since = 0;
+
+                        for i in start..mono_history.len() {
+                            notes_since += mono_history[i];
+                        }
+
+                        reps_penalty *= repetition_penalty(notes_since);
+
+                        break;
+                    }
+
+                    strain *= reps_penalty;
+
+                    *current_mono_len = 1;
+                } else {
+                    *current_mono_len += 1;
+                }
+
+                *prev_is_rim = Some(curr_is_rim);
+
+                strain
+            }
+            Self::Rhythm {
+                rhythm_history,
+                notes_since_rhythm_change,
+                current_strain,
+            } => {
+                let base_is_circle = current.base.is_circle();
+
+                if !base_is_circle {
+                    *current_strain = 0.0;
+                    *notes_since_rhythm_change = 0;
+
+                    return 0.0;
+                }
+
+                *current_strain *= RHYTHM_STRAIN_DECAY;
+                *notes_since_rhythm_change += 1;
+
+                if current.rhythm.difficulty.abs() < f32::EPSILON {
+                    return 0.0;
+                }
+
+                let mut strain = current.rhythm.difficulty;
+
+                rhythm_history.push(current.to_owned());
+
+                let mut reps_penalty = 1.0;
+
+                for most_recent_patterns_to_compare in 2..=RHYTHM_HISTORY_MAX_LEN / 2 {
+                    let iter = (0..rhythm_history
+                        .len()
+                        .saturating_sub(most_recent_patterns_to_compare))
+                        .rev();
+
+                    for start in iter {
+                        let different_pattern = (0..most_recent_patterns_to_compare).any(|i| {
+                            rhythm_history[start + i].rhythm
+                                != rhythm_history
+                                    [rhythm_history.len() + i - most_recent_patterns_to_compare]
+                                    .rhythm
+                        });
+
+                        if different_pattern {
+                            continue;
+                        }
+
+                        reps_penalty *= repetition_penalty(current.idx - rhythm_history[start].idx);
+
+                        break;
+                    }
+                }
+
+                let speed_penalty = if current.delta < 80.0 {
+                    1.0
+                } else if current.delta < 210.0 {
+                    (1.4 - 0.005 * current.delta).max(0.0)
+                } else {
+                    *current_strain = 0.0;
+                    *notes_since_rhythm_change = 0;
+
+                    0.0
+                };
+
+                strain *= reps_penalty;
+                strain *= pattern_len_penalty(*notes_since_rhythm_change);
+                strain *= speed_penalty;
+
+                *notes_since_rhythm_change = 0;
+                *current_strain += strain;
+
+                *current_strain
+            }
+            Self::Stamina {
+                hand,
+                note_pair_duration_history,
+                off_hand_object_duration,
+            } => {
+                let base_is_circle = current.base.is_circle();
+
+                if !base_is_circle {
+                    return 0.0;
+                }
+
+                if current.idx % 2 == *hand as usize {
+                    if current.idx == 1 {
+                        return 1.0;
+                    }
+
+                    let mut strain = 1.0;
+
+                    note_pair_duration_history.push(current.delta + *off_hand_object_duration);
+
+                    let shortest_recent_note = *note_pair_duration_history.min().unwrap();
+
+                    strain += speed_bonus(shortest_recent_note);
+
+                    if cheese[current.idx] {
+                        let p = cheese_penalty(current.delta + *off_hand_object_duration);
+                        strain *= p;
+                    }
+
+                    return strain;
+                }
+
+                *off_hand_object_duration = current.delta;
+
+                0.0
+            }
+        }
+    }
+}
+
+#[inline]
+fn pattern_len_penalty(pattern_len: usize) -> f32 {
+    let short_pattern_penalty = (0.15 * pattern_len as f32).min(1.0);
+    let long_pattern_penalty = (2.5 - 0.15 * pattern_len as f32).max(0.0).min(1.0);
+
+    short_pattern_penalty.min(long_pattern_penalty)
+}
+
+#[inline]
+fn cheese_penalty(note_pair_duration: f32) -> f32 {
+    if note_pair_duration > 125.0 {
+        1.0
+    } else if note_pair_duration < 100.0 {
+        0.6
+    } else {
+        0.6 + (note_pair_duration - 100.0) * 0.016
+    }
+}
+
+#[inline]
+fn speed_bonus(note_pair_duration: f32) -> f32 {
+    if note_pair_duration > 200.0 {
+        return 0.0;
+    }
+
+    let mut bonus = 200.0 - note_pair_duration;
+    bonus *= bonus;
+
+    bonus / 100_000.0
+}
+
+#[inline]
+fn repetition_penalty(notes_since: usize) -> f32 {
+    (0.032 * notes_since as f32).min(1.0)
+}

taiko/src/stamina_cheese.rs

@@ -0,0 +1,105 @@
+use super::{LimitedQueue, Rim};
+
+use parse::{Beatmap, HitObject};
+
+const ROLL_MIN_REPETITIONS: usize = 12;
+const TL_MIN_REPETITIONS: isize = 16;
+
+pub(crate) trait StaminaCheeseDetector {
+    fn find_cheese(&self) -> Vec<bool>;
+    fn find_rolls(&self, pattern_len: usize, cheese: &mut [bool]);
+    fn find_tl_tap(&self, parity: usize, is_rin: bool, cheese: &mut [bool]);
+}
+
+impl StaminaCheeseDetector for Beatmap {
+    fn find_cheese(&self) -> Vec<bool> {
+        let mut cheese = vec![false; self.hit_objects.len()];
+
+        self.find_rolls(3, &mut cheese);
+        self.find_rolls(4, &mut cheese);
+
+        self.find_tl_tap(0, true, &mut cheese);
+        self.find_tl_tap(1, true, &mut cheese);
+        self.find_tl_tap(0, false, &mut cheese);
+        self.find_tl_tap(1, false, &mut cheese);
+
+        cheese
+    }
+
+    fn find_rolls(&self, pattern_len: usize, cheese: &mut [bool]) {
+        let mut history = LimitedQueue::new(2 * pattern_len);
+
+        let mut index_before_last_repeat = -1;
+        let mut last_mark_end = 0;
+
+        for i in 0..self.hit_objects.len() {
+            history.push(&self.hit_objects[i]);
+
+            if !history.full() {
+                continue;
+            }
+
+            let contains = contains_pattern_repeat(&history, pattern_len);
+
+            if !contains {
+                index_before_last_repeat = (i + 1 - history.len()) as isize;
+                continue;
+            }
+
+            let repeated_len = (i as isize - index_before_last_repeat) as usize;
+
+            if repeated_len < ROLL_MIN_REPETITIONS {
+                continue;
+            }
+
+            mark_as_cheese(last_mark_end.max(i + 1 - repeated_len), i, cheese);
+
+            last_mark_end = i;
+        }
+    }
+
+    fn find_tl_tap(&self, parity: usize, is_rin: bool, cheese: &mut [bool]) {
+        let mut tl_len = -2;
+        let mut last_mark_end = 0;
+
+        for i in (parity..self.hit_objects.len()).step_by(2) {
+            if self.hit_objects[i].is_rim() == is_rin {
+                tl_len += 2;
+            } else {
+                tl_len = -2;
+            }
+
+            if tl_len < TL_MIN_REPETITIONS {
+                continue;
+            }
+
+            mark_as_cheese(
+                (i as isize + 1 - tl_len).max(last_mark_end as isize) as usize,
+                i,
+                cheese,
+            );
+
+            last_mark_end = i;
+        }
+    }
+}
+
+#[inline]
+fn mark_as_cheese(start: usize, end: usize, cheese: &mut [bool]) {
+    cheese
+        .iter_mut()
+        .take(end + 1)
+        .skip(start)
+        .for_each(|b| *b = true);
+}
+
+#[inline]
+fn contains_pattern_repeat(history: &LimitedQueue<&HitObject>, pattern_len: usize) -> bool {
+    for j in 0..pattern_len {
+        if history[j].is_rim() != history[j + pattern_len].is_rim() {
+            return false;
+        }
+    }
+
+    true
+}