store taiko strain peaks in CompactZerosVec

src/taiko/mod.rs

@@ -181,9 +181,9 @@ impl<'map> TaikoStars<'map> {
 
         TaikoStrains {
             section_len: SECTION_LEN,
-            color: colour,
-            rhythm,
-            stamina,
+            color: colour.to_vec(),
+            rhythm: rhythm.to_vec(),
+            stamina: stamina.to_vec(),
         }
     }
 }

src/taiko/skills/colour.rs

@@ -3,9 +3,12 @@ use std::{
     rc::{Rc, Weak},
 };
 
-use crate::taiko::{
-    colours::{AlternatingMonoPattern, MonoStreak, RepeatingHitPatterns},
-    difficulty_object::{ObjectLists, TaikoDifficultyObject},
+use crate::{
+    taiko::{
+        colours::{AlternatingMonoPattern, MonoStreak, RepeatingHitPatterns},
+        difficulty_object::{ObjectLists, TaikoDifficultyObject},
+    },
+    util::CompactZerosVec,
 };
 
 use super::{Skill, StrainDecaySkill, StrainSkill};
@@ -15,7 +18,7 @@ pub(crate) struct Colour {
     curr_strain: f64,
     curr_section_peak: f64,
     curr_section_end: f64,
-    pub(crate) strain_peaks: Vec<f64>,
+    pub(crate) strain_peaks: CompactZerosVec,
 }
 
 impl Colour {
@@ -24,7 +27,7 @@ impl Colour {
             curr_strain: 0.0,
             curr_section_peak: 0.0,
             curr_section_end: 0.0,
-            strain_peaks: Vec::new(),
+            strain_peaks: CompactZerosVec::new(),
         }
     }
 }
@@ -43,7 +46,7 @@ impl Skill for Colour {
 
 impl StrainSkill for Colour {
     #[inline]
-    fn strain_peaks_mut(&mut self) -> &mut Vec<f64> {
+    fn strain_peaks_mut(&mut self) -> &mut CompactZerosVec {
         &mut self.strain_peaks
     }
 

src/taiko/skills/peaks.rs

@@ -1,6 +1,9 @@
 use std::cmp::Ordering;
 
-use crate::taiko::difficulty_object::{ObjectLists, TaikoDifficultyObject};
+use crate::{
+    taiko::difficulty_object::{ObjectLists, TaikoDifficultyObject},
+    util::CompactZerosVec,
+};
 
 use super::{colour::Colour, rhythm::Rhythm, stamina::Stamina, Skill, StrainSkill};
 
@@ -74,9 +77,9 @@ impl Skill for Peaks {
         let stamina_peaks = self.stamina.get_curr_strain_peaks();
 
         let zip = colour_peaks
-            .into_iter()
-            .zip(rhythm_peaks)
-            .zip(stamina_peaks);
+            .iter()
+            .zip(rhythm_peaks.iter())
+            .zip(stamina_peaks.iter());
 
         for ((mut colour_peak, mut rhythm_peak), mut stamina_peak) in zip {
             colour_peak *= Self::COLOUR_SKILL_MULTIPLIER;
@@ -116,7 +119,7 @@ pub(crate) struct PeaksDifficultyValues {
 }
 
 pub(crate) struct PeaksRaw {
-    pub(crate) colour: Vec<f64>,
-    pub(crate) rhythm: Vec<f64>,
-    pub(crate) stamina: Vec<f64>,
+    pub(crate) colour: CompactZerosVec,
+    pub(crate) rhythm: CompactZerosVec,
+    pub(crate) stamina: CompactZerosVec,
 }

src/taiko/skills/rhythm.rs

@@ -1,6 +1,6 @@
 use crate::{
     taiko::difficulty_object::{HitObjectRhythm, ObjectLists, TaikoDifficultyObject},
-    util::LimitedQueue,
+    util::{CompactZerosVec, LimitedQueue},
 };
 
 use super::{Skill, StrainDecaySkill, StrainSkill};
@@ -17,7 +17,7 @@ pub(crate) struct Rhythm {
     history: LimitedQueue<HistoryElement, HISTORY_MAX_LEN>,
     curr_section_peak: f64,
     curr_section_end: f64,
-    pub(crate) strain_peaks: Vec<f64>,
+    pub(crate) strain_peaks: CompactZerosVec,
 }
 
 impl Rhythm {
@@ -31,7 +31,7 @@ impl Rhythm {
             history: LimitedQueue::new(),
             curr_section_peak: 0.0,
             curr_section_end: 0.0,
-            strain_peaks: Vec::new(),
+            strain_peaks: CompactZerosVec::new(),
         }
     }
 
@@ -113,7 +113,7 @@ impl Skill for Rhythm {
 
 impl StrainSkill for Rhythm {
     #[inline]
-    fn strain_peaks_mut(&mut self) -> &mut Vec<f64> {
+    fn strain_peaks_mut(&mut self) -> &mut CompactZerosVec {
         &mut self.strain_peaks
     }
 

src/taiko/skills/stamina.rs

@@ -1,4 +1,7 @@
-use crate::taiko::difficulty_object::{ObjectLists, TaikoDifficultyObject};
+use crate::{
+    taiko::difficulty_object::{ObjectLists, TaikoDifficultyObject},
+    util::CompactZerosVec,
+};
 
 use super::{Skill, StrainDecaySkill, StrainSkill};
 
@@ -7,7 +10,7 @@ pub(crate) struct Stamina {
     curr_strain: f64,
     curr_section_peak: f64,
     curr_section_end: f64,
-    pub(crate) strain_peaks: Vec<f64>,
+    pub(crate) strain_peaks: CompactZerosVec,
 }
 
 impl Stamina {
@@ -16,7 +19,7 @@ impl Stamina {
             curr_strain: 0.0,
             curr_section_peak: 0.0,
             curr_section_end: 0.0,
-            strain_peaks: Vec::new(),
+            strain_peaks: CompactZerosVec::new(),
         }
     }
 }
@@ -35,7 +38,7 @@ impl Skill for Stamina {
 
 impl StrainSkill for Stamina {
     #[inline]
-    fn strain_peaks_mut(&mut self) -> &mut Vec<f64> {
+    fn strain_peaks_mut(&mut self) -> &mut CompactZerosVec {
         &mut self.strain_peaks
     }
 

src/taiko/skills/traits.rs

@@ -1,8 +1,11 @@
 use std::{cmp::Ordering, mem};
 
-use crate::taiko::{
-    difficulty_object::{ObjectLists, TaikoDifficultyObject},
-    SECTION_LEN,
+use crate::{
+    taiko::{
+        difficulty_object::{ObjectLists, TaikoDifficultyObject},
+        SECTION_LEN,
+    },
+    util::CompactZerosVec,
 };
 
 pub(crate) trait Skill: Sized {
@@ -13,7 +16,7 @@ pub(crate) trait Skill: Sized {
 pub(crate) trait StrainSkill: Skill {
     const DECAY_WEIGHT: f64 = 0.9;
 
-    fn strain_peaks_mut(&mut self) -> &mut Vec<f64>;
+    fn strain_peaks_mut(&mut self) -> &mut CompactZerosVec;
     fn curr_section_peak(&mut self) -> &mut f64;
     fn curr_section_end(&mut self) -> &mut f64;
 
@@ -76,9 +79,7 @@ pub(crate) trait StrainSkill: Skill {
 
         // * Sections with 0 strain are excluded to avoid worst-case time complexity of the following sort (e.g. /b/2351871).
         // * These sections will not contribute to the difficulty.
-        let mut peaks = self.get_curr_strain_peaks();
-
-        peaks.retain(|&peak| peak > 0.0);
+        let mut peaks = self.get_curr_strain_peaks().to_non_zeros();
         peaks.sort_unstable_by(|a, b| b.partial_cmp(a).unwrap_or(Ordering::Equal));
 
         // * Difficulty is the weighted sum of the highest strains from every section.
@@ -92,7 +93,7 @@ pub(crate) trait StrainSkill: Skill {
     }
 
     #[inline]
-    fn get_curr_strain_peaks(mut self) -> Vec<f64> {
+    fn get_curr_strain_peaks(mut self) -> CompactZerosVec {
         let curr_peak = *self.curr_section_peak();
         let mut strain_peaks = mem::take(self.strain_peaks_mut());
         strain_peaks.push(curr_peak);

src/util/compact_zeros.rs

@@ -0,0 +1,110 @@
+use std::{
+    iter::{self, Copied},
+    slice,
+};
+
+#[derive(Clone, Debug, Default)]
+pub(crate) struct CompactZerosVec {
+    inner: Vec<Number>,
+    non_zero_count: usize,
+}
+
+impl CompactZerosVec {
+    pub(crate) fn new() -> Self {
+        Self::default()
+    }
+
+    pub(crate) fn push(&mut self, num: f64) {
+        if num.abs() > f64::EPSILON {
+            self.inner.push(Number::NonZero(num));
+            self.non_zero_count += 1;
+        } else {
+            self.push_n_zeros(1);
+        }
+    }
+
+    pub(crate) fn push_n_zeros(&mut self, n: usize) {
+        match self.inner.last_mut() {
+            Some(Number::NonZero(_)) | None => self.inner.push(Number::Zeros(n)),
+            Some(Number::Zeros(zeros)) => *zeros += n,
+        }
+    }
+
+    pub(crate) fn to_non_zeros(&self) -> Vec<f64> {
+        let mut non_zeros = Vec::with_capacity(self.non_zero_count);
+
+        let iter = self.inner.iter().filter_map(|num| match num {
+            Number::NonZero(n) => Some(*n),
+            Number::Zeros(_) => None,
+        });
+
+        non_zeros.extend(iter);
+
+        non_zeros
+    }
+
+    pub(crate) fn iter(&self) -> Iter<'_> {
+        Iter::new(self)
+    }
+
+    pub(crate) fn to_vec(&self) -> Vec<f64> {
+        let mut nums = Vec::with_capacity(self.inner.len() * 2);
+
+        for &num in self.inner.iter() {
+            match num {
+                Number::NonZero(num) => nums.push(num),
+                Number::Zeros(zeros) => nums.extend(iter::repeat(0.0).take(zeros)),
+            }
+        }
+
+        nums
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+enum Number {
+    NonZero(f64),
+    Zeros(usize),
+}
+
+pub(crate) struct Iter<'a> {
+    iter: Copied<slice::Iter<'a, Number>>,
+    curr: Option<Number>,
+}
+
+impl<'a> Iter<'a> {
+    fn new(compact_zeros: &'a CompactZerosVec) -> Self {
+        let mut iter = compact_zeros.inner.iter().copied();
+
+        Self {
+            curr: iter.next(),
+            iter,
+        }
+    }
+}
+
+impl Iterator for Iter<'_> {
+    type Item = f64;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.curr.as_mut()? {
+            Number::NonZero(n) => {
+                let n = *n;
+                self.curr = self.iter.next();
+
+                Some(n)
+            }
+            Number::Zeros(zeros @ 1..) => {
+                *zeros -= 1;
+
+                Some(0.0)
+            }
+            Number::Zeros(_) => {
+                self.curr = self.iter.next();
+
+                self.next()
+            }
+        }
+    }
+}

src/util/mod.rs

@@ -1,4 +1,5 @@
 mod byte_hasher;
+mod compact_zeros;
 mod float_ext;
 mod limited_queue;
 mod sorted_vec;
@@ -7,6 +8,6 @@ mod tandem_sort;
 pub use self::sorted_vec::SortedVec;
 
 pub(crate) use self::{
-    byte_hasher::ByteHasher, float_ext::FloatExt, limited_queue::LimitedQueue,
-    tandem_sort::TandemSorter,
+    byte_hasher::ByteHasher, compact_zeros::CompactZerosVec, float_ext::FloatExt,
+    limited_queue::LimitedQueue, tandem_sort::TandemSorter,
 };