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Refactor difficulty calculation flow to move control from DifficultyCalculator to Skills #38529

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Refactor difficulty calculation flow to move control from DifficultyCalculator to Skills #38529

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0683ee4
Refactor difficulty calculation flow to move control from `Difficulty…
stanriders Aug 5, 2026
bf7cbfe
Make skill attributes properties `required`
stanriders Aug 5, 2026
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4 changes: 2 additions & 2 deletions ...lesets/ruleset-empty/osu.Game.Rulesets.EmptyFreeform/EmptyFreeformDifficultyCalculator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,13 +19,13 @@ public EmptyFreeformDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap b
{
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skills)
{
return new DifficultyAttributes(mods, 0);
}

protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, Mod[] mods) => Enumerable.Empty<DifficultyHitObject>();

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods) => Array.Empty<Skill>();
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects) => Array.Empty<ISkill>();
}
}
4 changes: 2 additions & 2 deletions ...lates/Rulesets/ruleset-example/osu.Game.Rulesets.Pippidon/PippidonDifficultyCalculator.cs
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Expand Up @@ -19,13 +19,13 @@ public PippidonDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatma
{
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skills)
{
return new DifficultyAttributes(mods, 0);
}

protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, Mod[] mods) => Enumerable.Empty<DifficultyHitObject>();

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods) => Array.Empty<Skill>();
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects) => Array.Empty<ISkill>();
}
}
4 changes: 2 additions & 2 deletions ...et-scrolling-empty/osu.Game.Rulesets.EmptyScrolling/EmptyScrollingDifficultyCalculator.cs
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Expand Up @@ -19,13 +19,13 @@ public EmptyScrollingDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap
{
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skills)
{
return new DifficultyAttributes(mods, 0);
}

protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, Mod[] mods) => Enumerable.Empty<DifficultyHitObject>();

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods) => Array.Empty<Skill>();
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects) => Array.Empty<ISkill>();
}
}
4 changes: 2 additions & 2 deletions ...sets/ruleset-scrolling-example/osu.Game.Rulesets.Pippidon/PippidonDifficultyCalculator.cs
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Expand Up @@ -19,13 +19,13 @@ public PippidonDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatma
{
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skills)
{
return new DifficultyAttributes(mods, 0);
}

protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, Mod[] mods) => Enumerable.Empty<DifficultyHitObject>();

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods) => Array.Empty<Skill>();
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects) => Array.Empty<ISkill>();
}
}
12 changes: 12 additions & 0 deletions osu.Game.Benchmarks/BenchmarkDifficultyCalculation.cs
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Expand Up @@ -65,6 +65,18 @@ private WorkingBeatmap readBeatmap(ZipArchiveReader archiveReader, string beatma
[Benchmark]
public void CalculateDifficultyMania() => maniaCalculator.Calculate();

[Benchmark]
public void CalculateTimedDifficultyOsu() => osuCalculator.CalculateTimed();

[Benchmark]
public void CalculateTimedDifficultyTaiko() => taikoCalculator.CalculateTimed();

[Benchmark]
public void CalculateTimedDifficultyCatch() => catchCalculator.CalculateTimed();

[Benchmark]
public void CalculateTimedDifficultyMania() => maniaCalculator.CalculateTimed();

[Benchmark]
public void CalculateDifficultyOsuHundredTimes()
{
Expand Down
11 changes: 5 additions & 6 deletions osu.Game.Rulesets.Catch/Difficulty/CatchDifficultyCalculator.cs
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Expand Up @@ -3,7 +3,6 @@

using System;
using System.Collections.Generic;
using System.Linq;
using osu.Game.Beatmaps;
using osu.Game.Rulesets.Catch.Beatmaps;
using osu.Game.Rulesets.Catch.Difficulty.Preprocessing;
Expand All @@ -30,14 +29,14 @@ public CatchDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
{
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skillAttributes)
{
if (beatmap.HitObjects.Count == 0)
return new CatchDifficultyAttributes { Mods = mods };

CatchDifficultyAttributes attributes = new CatchDifficultyAttributes
{
StarRating = Math.Sqrt(skills.OfType<Movement>().Single().DifficultyValue()) * difficulty_multiplier,
StarRating = Math.Sqrt(skillAttributes[0].Difficulty) * difficulty_multiplier,
Mods = mods,
MaxCombo = beatmap.GetMaxCombo(),
};
Expand Down Expand Up @@ -74,11 +73,11 @@ protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(I
return objects;
}

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods)
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects)
{
return new Skill[]
return new ISkill[]
{
new Movement(mods),
new Movement(mods, difficultyHitObjects),
};
}

Expand Down
4 changes: 2 additions & 2 deletions osu.Game.Rulesets.Catch/Difficulty/Skills/Movement.cs
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Expand Up @@ -17,8 +17,8 @@ public class Movement : StrainDecaySkill

protected override int SectionLength => 750;

public Movement(Mod[] mods)
: base(mods)
public Movement(Mod[] mods, DifficultyHitObject[] difficultyHitObjects)
: base(mods, difficultyHitObjects)
{
}

Expand Down
8 changes: 4 additions & 4 deletions osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyCalculator.cs
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Expand Up @@ -37,7 +37,7 @@ public ManiaDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
isForCurrentRuleset = beatmap.BeatmapInfo.Ruleset.MatchesOnlineID(ruleset);
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skillAttributes)
{
if (beatmap.HitObjects.Count == 0)
return new ManiaDifficultyAttributes { Mods = mods };
Expand All @@ -47,7 +47,7 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat

ManiaDifficultyAttributes attributes = new ManiaDifficultyAttributes
{
StarRating = skills.OfType<Strain>().Single().DifficultyValue() * difficulty_multiplier,
StarRating = skillAttributes[0].Difficulty * difficulty_multiplier,
Mods = mods,
MaxCombo = beatmap.HitObjects.Sum(maxComboForObject),
};
Expand Down Expand Up @@ -91,9 +91,9 @@ protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(I
// Sorting is done in CreateDifficultyHitObjects, since the full list of hitobjects is required.
protected override IEnumerable<DifficultyHitObject> SortObjects(IEnumerable<DifficultyHitObject> input) => input;

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods) => new Skill[]
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects) => new ISkill[]
{
new Strain(mods, ((ManiaBeatmap)Beatmap).TotalColumns)
new Strain(mods, difficultyHitObjects, ((ManiaBeatmap)Beatmap).TotalColumns)
};

protected override Mod[] DifficultyAdjustmentMods
Expand Down
4 changes: 2 additions & 2 deletions osu.Game.Rulesets.Mania/Difficulty/Skills/Strain.cs
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Expand Up @@ -23,8 +23,8 @@ public class Strain : StrainDecaySkill
private double highestIndividualStrain;
private double overallStrain;

public Strain(Mod[] mods, int totalColumns)
: base(mods)
public Strain(Mod[] mods, DifficultyHitObject[] difficultyHitObjects, int totalColumns)
: base(mods, difficultyHitObjects)
{
individualStrains = new double[totalColumns];
overallStrain = 1;
Expand Down
8 changes: 8 additions & 0 deletions osu.Game.Rulesets.Osu.Tests/OsuDifficultyCalculatorTest.cs
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Expand Up @@ -25,6 +25,14 @@ public class OsuDifficultyCalculatorTest : DifficultyCalculatorTest
public void Test(double expectedStarRating, int expectedMaxCombo, string name)
=> base.Test(expectedStarRating, expectedMaxCombo, name);

[TestCase(6.5243170265483581d, 239, "diffcalc-test")]
[TestCase(1.3280410795791415d, 54, "zero-length-sliders")]
[TestCase(0.40867325147697559d, 4, "very-fast-slider")]
[TestCase(0.87058175794353554d, 6, "nan-slider")]
[TestCase(6.3059767387139756d, 2359, "801165")] // real world test
public void TestTimed(double expectedStarRating, int expectedMaxCombo, string name)
=> base.TestTimed(expectedStarRating, expectedMaxCombo, name);

[TestCase(9.4677607900646308d, 239, "diffcalc-test")]
[TestCase(1.6856612715618886d, 54, "zero-length-sliders")]
[TestCase(0.53588473186572561d, 4, "very-fast-slider")]
Expand Down
72 changes: 27 additions & 45 deletions osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyCalculator.cs
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Expand Up @@ -28,58 +28,40 @@ public OsuDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
{
}

protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills)
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, IReadOnlyList<ISkillAttributes> skillAttributes)
{
if (beatmap.HitObjects.Count == 0)
return new OsuDifficultyAttributes { Mods = mods };

var aim = skills.OfType<Aim>().Single(a => a.IncludeSliders);
var aimWithoutSliders = skills.OfType<Aim>().Single(a => !a.IncludeSliders);
var speed = skills.OfType<Speed>().Single();
var flashlight = skills.OfType<Flashlight>().SingleOrDefault();
var reading = skills.OfType<Reading>().Single();
var aimAttributes = skillAttributes.OfType<AimAttributes>().Single(a => a.WithSliders);
var aimWithoutSlidersAttributes = skillAttributes.OfType<AimAttributes>().Single(a => !a.WithSliders);
var speedAttributes = skillAttributes.OfType<SpeedAttributes>().Single();
var flashlightAttributes = skillAttributes.OfType<FlashlightAttributes>().SingleOrDefault();
var readingAttributes = skillAttributes.OfType<ReadingAttributes>().Single();

double aimDifficultyValue = aim.DifficultyValue();
double aimNoSlidersDifficultyValue = aimWithoutSliders.DifficultyValue();
double speedDifficultyValue = speed.DifficultyValue();
double readingDifficultyValue = reading.DifficultyValue();

double aimDifficultStrainCount = aim.CountTopWeightedStrains(aimDifficultyValue);
double speedDifficultStrainCount = speed.CountTopWeightedObjectDifficulties(speedDifficultyValue);
double readingDifficultNoteCount = reading.CountTopWeightedObjectDifficulties(readingDifficultyValue);

double speedNotes = speed.RelevantObjectCount();

double aimNoSlidersTopWeightedSliderCount = aimWithoutSliders.CountTopWeightedSliders(aimNoSlidersDifficultyValue);
double aimNoSlidersDifficultStrainCount = aimWithoutSliders.CountTopWeightedStrains(aimNoSlidersDifficultyValue);

double aimTopWeightedSliderFactor = aimNoSlidersTopWeightedSliderCount / Math.Max(1, aimNoSlidersDifficultStrainCount - aimNoSlidersTopWeightedSliderCount);

double speedTopWeightedSliderCount = speed.CountTopWeightedSliders(speedDifficultyValue);
double speedTopWeightedSliderFactor = speedTopWeightedSliderCount / Math.Max(1, speedDifficultStrainCount - speedTopWeightedSliderCount);

double difficultSliders = aim.GetDifficultSliders();
double aimTopWeightedSliderFactor = aimWithoutSlidersAttributes.TopWeightedSlidersCount / Math.Max(1, aimWithoutSlidersAttributes.TopWeightedStrainsCount - aimWithoutSlidersAttributes.TopWeightedSlidersCount);
double speedTopWeightedSliderFactor = speedAttributes.TopWeightedSlidersCount / Math.Max(1, speedAttributes.TopWeightedObjectDifficultiesCount - speedAttributes.TopWeightedSlidersCount);

int hitCircleCount = beatmap.HitObjects.Count(h => h is HitCircle);
int sliderCount = beatmap.HitObjects.Count(h => h is Slider);
int spinnerCount = beatmap.HitObjects.Count(h => h is Spinner);

int totalHits = beatmap.HitObjects.Count;

double aimRating = calculateAimDifficultyRating(aimDifficultyValue);
double aimNoSlidersRating = calculateAimDifficultyRating(aimNoSlidersDifficultyValue);
double aimRating = calculateAimDifficultyRating(aimAttributes.Difficulty);
double aimNoSlidersRating = calculateAimDifficultyRating(aimWithoutSlidersAttributes.Difficulty);

double sliderFactor = aimDifficultyValue > 0
double sliderFactor = aimAttributes.Difficulty > 0
? aimNoSlidersRating / aimRating
: 1;

double speedRating = calculateDifficultyRating(speedDifficultyValue);
double readingRating = calculateDifficultyRating(readingDifficultyValue);
double speedRating = calculateDifficultyRating(speedAttributes.Difficulty);
double readingRating = calculateDifficultyRating(readingAttributes.Difficulty);

double flashlightRating = 0.0;

if (flashlight is not null)
flashlightRating = calculateDifficultyRating(flashlight.DifficultyValue());
if (flashlightAttributes is not null)
flashlightRating = calculateDifficultyRating(flashlightAttributes.Difficulty);

double sliderNestedScorePerObject = LegacyScoreUtils.CalculateNestedScorePerObject(beatmap, totalHits);
double legacyScoreBaseMultiplier = LegacyScoreUtils.CalculateDifficultyPeppyStars(WorkingBeatmap.Beatmap);
Expand All @@ -102,15 +84,15 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
StarRating = starRating,
Mods = mods,
AimDifficulty = aimRating,
AimDifficultSliderCount = difficultSliders,
AimDifficultSliderCount = aimAttributes.DifficultSlidersCount,
SpeedDifficulty = speedRating,
SpeedNoteCount = speedNotes,
SpeedNoteCount = speedAttributes.RelevantObjectCount,
FlashlightDifficulty = flashlightRating,
ReadingDifficulty = readingRating,
SliderFactor = sliderFactor,
AimDifficultStrainCount = aimDifficultStrainCount,
SpeedDifficultStrainCount = speedDifficultStrainCount,
ReadingDifficultNoteCount = readingDifficultNoteCount,
AimDifficultStrainCount = aimAttributes.TopWeightedStrainsCount,
SpeedDifficultStrainCount = speedAttributes.TopWeightedObjectDifficultiesCount,
ReadingDifficultNoteCount = readingAttributes.TopWeightedObjectDifficultiesCount,
AimTopWeightedSliderFactor = aimTopWeightedSliderFactor,
SpeedTopWeightedSliderFactor = speedTopWeightedSliderFactor,
MaxCombo = beatmap.GetMaxCombo(),
Expand Down Expand Up @@ -162,18 +144,18 @@ protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(I
return objects;
}

protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods)
protected override ISkill[] CreateSkills(IBeatmap beatmap, Mod[] mods, DifficultyHitObject[] difficultyHitObjects)
{
var skills = new List<Skill>
var skills = new List<ISkill>
{
new Aim(mods, true),
new Aim(mods, false),
new Speed(mods),
new Reading(mods)
new Aim(mods, difficultyHitObjects, true),
new Aim(mods, difficultyHitObjects, false),
new Speed(mods, difficultyHitObjects),
new Reading(mods, difficultyHitObjects)
};

if (mods.Any(h => h is OsuModFlashlight))
skills.Add(new Flashlight(mods, beatmap.HitObjects.Count));
skills.Add(new Flashlight(mods, difficultyHitObjects, beatmap.HitObjects.Count));

return skills.ToArray();
}
Expand Down
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