Merge pull request #9637 from smoogipoo/beatmap-difficulty-manager

Add dynamic computation of beatmap difficulty

osu.Game/Beatmaps/BeatmapDifficultyManager.cs

@@ -0,0 +1,278 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using JetBrains.Annotations;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Lists;
+using osu.Framework.Threading;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Mods;
+
+namespace osu.Game.Beatmaps
+{
+    public class BeatmapDifficultyManager : CompositeDrawable
+    {
+        // Too many simultaneous updates can lead to stutters. One thread seems to work fine for song select display purposes.
+        private readonly ThreadedTaskScheduler updateScheduler = new ThreadedTaskScheduler(1, nameof(BeatmapDifficultyManager));
+
+        // A permanent cache to prevent re-computations.
+        private readonly ConcurrentDictionary<DifficultyCacheLookup, StarDifficulty> difficultyCache = new ConcurrentDictionary<DifficultyCacheLookup, StarDifficulty>();
+
+        // All bindables that should be updated along with the current ruleset + mods.
+        private readonly LockedWeakList<BindableStarDifficulty> trackedBindables = new LockedWeakList<BindableStarDifficulty>();
+
+        [Resolved]
+        private BeatmapManager beatmapManager { get; set; }
+
+        [Resolved]
+        private Bindable<RulesetInfo> currentRuleset { get; set; }
+
+        [Resolved]
+        private Bindable<IReadOnlyList<Mod>> currentMods { get; set; }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            currentRuleset.BindValueChanged(_ => updateTrackedBindables());
+            currentMods.BindValueChanged(_ => updateTrackedBindables(), true);
+        }
+
+        /// <summary>
+        /// Retrieves a bindable containing the star difficulty of a <see cref="BeatmapInfo"/> that follows the currently-selected ruleset and mods.
+        /// </summary>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> to get the difficulty of.</param>
+        /// <param name="cancellationToken">An optional <see cref="CancellationToken"/> which stops updating the star difficulty for the given <see cref="BeatmapInfo"/>.</param>
+        /// <returns>A bindable that is updated to contain the star difficulty when it becomes available.</returns>
+        public IBindable<StarDifficulty> GetBindableDifficulty([NotNull] BeatmapInfo beatmapInfo, CancellationToken cancellationToken = default)
+        {
+            var bindable = createBindable(beatmapInfo, currentRuleset.Value, currentMods.Value, cancellationToken);
+            trackedBindables.Add(bindable);
+            return bindable;
+        }
+
+        /// <summary>
+        /// Retrieves a bindable containing the star difficulty of a <see cref="BeatmapInfo"/> with a given <see cref="RulesetInfo"/> and <see cref="Mod"/> combination.
+        /// </summary>
+        /// <remarks>
+        /// The bindable will not update to follow the currently-selected ruleset and mods.
+        /// </remarks>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> to get the difficulty of.</param>
+        /// <param name="rulesetInfo">The <see cref="RulesetInfo"/> to get the difficulty with. If <c>null</c>, the <paramref name="beatmapInfo"/>'s ruleset is used.</param>
+        /// <param name="mods">The <see cref="Mod"/>s to get the difficulty with. If <c>null</c>, no mods will be assumed.</param>
+        /// <param name="cancellationToken">An optional <see cref="CancellationToken"/> which stops updating the star difficulty for the given <see cref="BeatmapInfo"/>.</param>
+        /// <returns>A bindable that is updated to contain the star difficulty when it becomes available.</returns>
+        public IBindable<StarDifficulty> GetBindableDifficulty([NotNull] BeatmapInfo beatmapInfo, [CanBeNull] RulesetInfo rulesetInfo, [CanBeNull] IEnumerable<Mod> mods,
+                                                               CancellationToken cancellationToken = default)
+            => createBindable(beatmapInfo, rulesetInfo, mods, cancellationToken);
+
+        /// <summary>
+        /// Retrieves the difficulty of a <see cref="BeatmapInfo"/>.
+        /// </summary>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> to get the difficulty of.</param>
+        /// <param name="rulesetInfo">The <see cref="RulesetInfo"/> to get the difficulty with.</param>
+        /// <param name="mods">The <see cref="Mod"/>s to get the difficulty with.</param>
+        /// <param name="cancellationToken">An optional <see cref="CancellationToken"/> which stops computing the star difficulty.</param>
+        /// <returns>The <see cref="StarDifficulty"/>.</returns>
+        public async Task<StarDifficulty> GetDifficultyAsync([NotNull] BeatmapInfo beatmapInfo, [CanBeNull] RulesetInfo rulesetInfo = null, [CanBeNull] IEnumerable<Mod> mods = null,
+                                                             CancellationToken cancellationToken = default)
+        {
+            if (tryGetExisting(beatmapInfo, rulesetInfo, mods, out var existing, out var key))
+                return existing;
+
+            return await Task.Factory.StartNew(() => computeDifficulty(key, beatmapInfo, rulesetInfo), cancellationToken,
+                TaskCreationOptions.HideScheduler | TaskCreationOptions.RunContinuationsAsynchronously, updateScheduler);
+        }
+
+        /// <summary>
+        /// Retrieves the difficulty of a <see cref="BeatmapInfo"/>.
+        /// </summary>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> to get the difficulty of.</param>
+        /// <param name="rulesetInfo">The <see cref="RulesetInfo"/> to get the difficulty with.</param>
+        /// <param name="mods">The <see cref="Mod"/>s to get the difficulty with.</param>
+        /// <returns>The <see cref="StarDifficulty"/>.</returns>
+        public StarDifficulty GetDifficulty([NotNull] BeatmapInfo beatmapInfo, [CanBeNull] RulesetInfo rulesetInfo = null, [CanBeNull] IEnumerable<Mod> mods = null)
+        {
+            if (tryGetExisting(beatmapInfo, rulesetInfo, mods, out var existing, out var key))
+                return existing;
+
+            return computeDifficulty(key, beatmapInfo, rulesetInfo);
+        }
+
+        private CancellationTokenSource trackedUpdateCancellationSource;
+
+        /// <summary>
+        /// Updates all tracked <see cref="BindableStarDifficulty"/> using the current ruleset and mods.
+        /// </summary>
+        private void updateTrackedBindables()
+        {
+            trackedUpdateCancellationSource?.Cancel();
+            trackedUpdateCancellationSource = new CancellationTokenSource();
+
+            foreach (var b in trackedBindables)
+            {
+                if (trackedUpdateCancellationSource.IsCancellationRequested)
+                    break;
+
+                using (var linkedSource = CancellationTokenSource.CreateLinkedTokenSource(trackedUpdateCancellationSource.Token, b.CancellationToken))
+                    updateBindable(b, currentRuleset.Value, currentMods.Value, linkedSource.Token);
+            }
+        }
+
+        /// <summary>
+        /// Updates the value of a <see cref="BindableStarDifficulty"/> with a given ruleset + mods.
+        /// </summary>
+        /// <param name="bindable">The <see cref="BindableStarDifficulty"/> to update.</param>
+        /// <param name="rulesetInfo">The <see cref="RulesetInfo"/> to update with.</param>
+        /// <param name="mods">The <see cref="Mod"/>s to update with.</param>
+        /// <param name="cancellationToken">A token that may be used to cancel this update.</param>
+        private void updateBindable([NotNull] BindableStarDifficulty bindable, [CanBeNull] RulesetInfo rulesetInfo, [CanBeNull] IEnumerable<Mod> mods, CancellationToken cancellationToken = default)
+        {
+            GetDifficultyAsync(bindable.Beatmap, rulesetInfo, mods, cancellationToken).ContinueWith(t =>
+            {
+                // We're on a threadpool thread, but we should exit back to the update thread so consumers can safely handle value-changed events.
+                Schedule(() =>
+                {
+                    if (!cancellationToken.IsCancellationRequested)
+                        bindable.Value = t.Result;
+                });
+            }, cancellationToken);
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="BindableStarDifficulty"/> and triggers an initial value update.
+        /// </summary>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> that star difficulty should correspond to.</param>
+        /// <param name="initialRulesetInfo">The initial <see cref="RulesetInfo"/> to get the difficulty with.</param>
+        /// <param name="initialMods">The initial <see cref="Mod"/>s to get the difficulty with.</param>
+        /// <param name="cancellationToken">An optional <see cref="CancellationToken"/> which stops updating the star difficulty for the given <see cref="BeatmapInfo"/>.</param>
+        /// <returns>The <see cref="BindableStarDifficulty"/>.</returns>
+        private BindableStarDifficulty createBindable([NotNull] BeatmapInfo beatmapInfo, [CanBeNull] RulesetInfo initialRulesetInfo, [CanBeNull] IEnumerable<Mod> initialMods,
+                                                      CancellationToken cancellationToken)
+        {
+            var bindable = new BindableStarDifficulty(beatmapInfo, cancellationToken);
+            updateBindable(bindable, initialRulesetInfo, initialMods, cancellationToken);
+            return bindable;
+        }
+
+        /// <summary>
+        /// Computes the difficulty defined by a <see cref="DifficultyCacheLookup"/> key, and stores it to the timed cache.
+        /// </summary>
+        /// <param name="key">The <see cref="DifficultyCacheLookup"/> that defines the computation parameters.</param>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> to compute the difficulty of.</param>
+        /// <param name="rulesetInfo">The <see cref="RulesetInfo"/> to compute the difficulty with.</param>
+        /// <returns>The <see cref="StarDifficulty"/>.</returns>
+        private StarDifficulty computeDifficulty(in DifficultyCacheLookup key, BeatmapInfo beatmapInfo, RulesetInfo rulesetInfo)
+        {
+            // In the case that the user hasn't given us a ruleset, use the beatmap's default ruleset.
+            rulesetInfo ??= beatmapInfo.Ruleset;
+
+            try
+            {
+                var ruleset = rulesetInfo.CreateInstance();
+                Debug.Assert(ruleset != null);
+
+                var calculator = ruleset.CreateDifficultyCalculator(beatmapManager.GetWorkingBeatmap(beatmapInfo));
+                var attributes = calculator.Calculate(key.Mods);
+
+                return difficultyCache[key] = new StarDifficulty(attributes.StarRating);
+            }
+            catch
+            {
+                return difficultyCache[key] = new StarDifficulty(0);
+            }
+        }
+
+        /// <summary>
+        /// Attempts to retrieve an existing difficulty for the combination.
+        /// </summary>
+        /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/>.</param>
+        /// <param name="rulesetInfo">The <see cref="RulesetInfo"/>.</param>
+        /// <param name="mods">The <see cref="Mod"/>s.</param>
+        /// <param name="existingDifficulty">The existing difficulty value, if present.</param>
+        /// <param name="key">The <see cref="DifficultyCacheLookup"/> key that was used to perform this lookup. This can be further used to query <see cref="computeDifficulty"/>.</param>
+        /// <returns>Whether an existing difficulty was found.</returns>
+        private bool tryGetExisting(BeatmapInfo beatmapInfo, RulesetInfo rulesetInfo, IEnumerable<Mod> mods, out StarDifficulty existingDifficulty, out DifficultyCacheLookup key)
+        {
+            // In the case that the user hasn't given us a ruleset, use the beatmap's default ruleset.
+            rulesetInfo ??= beatmapInfo.Ruleset;
+
+            // Difficulty can only be computed if the beatmap and ruleset are locally available.
+            if (beatmapInfo.ID == 0 || rulesetInfo.ID == null)
+            {
+                // If not, fall back to the existing star difficulty (e.g. from an online source).
+                existingDifficulty = new StarDifficulty(beatmapInfo.StarDifficulty);
+                key = default;
+
+                return true;
+            }
+
+            key = new DifficultyCacheLookup(beatmapInfo.ID, rulesetInfo.ID.Value, mods);
+            return difficultyCache.TryGetValue(key, out existingDifficulty);
+        }
+
+        private readonly struct DifficultyCacheLookup : IEquatable<DifficultyCacheLookup>
+        {
+            public readonly int BeatmapId;
+            public readonly int RulesetId;
+            public readonly Mod[] Mods;
+
+            public DifficultyCacheLookup(int beatmapId, int rulesetId, IEnumerable<Mod> mods)
+            {
+                BeatmapId = beatmapId;
+                RulesetId = rulesetId;
+                Mods = mods?.OrderBy(m => m.Acronym).ToArray() ?? Array.Empty<Mod>();
+            }
+
+            public bool Equals(DifficultyCacheLookup other)
+                => BeatmapId == other.BeatmapId
+                   && RulesetId == other.RulesetId
+                   && Mods.SequenceEqual(other.Mods);
+
+            public override int GetHashCode()
+            {
+                var hashCode = new HashCode();
+
+                hashCode.Add(BeatmapId);
+                hashCode.Add(RulesetId);
+                foreach (var mod in Mods)
+                    hashCode.Add(mod.Acronym);
+
+                return hashCode.ToHashCode();
+            }
+        }
+
+        private class BindableStarDifficulty : Bindable<StarDifficulty>
+        {
+            public readonly BeatmapInfo Beatmap;
+            public readonly CancellationToken CancellationToken;
+
+            public BindableStarDifficulty(BeatmapInfo beatmap, CancellationToken cancellationToken)
+            {
+                Beatmap = beatmap;
+                CancellationToken = cancellationToken;
+            }
+        }
+    }
+
+    public readonly struct StarDifficulty
+    {
+        public readonly double Stars;
+
+        public StarDifficulty(double stars)
+        {
+            Stars = stars;
+
+            // Todo: Add more members (BeatmapInfo.DifficultyRating? Attributes? Etc...)
+        }
+    }
+}

osu.Game/OsuGameBase.cs

@@ -199,6 +199,10 @@ namespace osu.Game
                     ScoreManager.Undelete(getBeatmapScores(item), true);
             });
 
+            var difficultyManager = new BeatmapDifficultyManager();
+            dependencies.Cache(difficultyManager);
+            AddInternal(difficultyManager);
+
             dependencies.Cache(KeyBindingStore = new KeyBindingStore(contextFactory, RulesetStore));
             dependencies.Cache(SettingsStore = new SettingsStore(contextFactory));
             dependencies.Cache(RulesetConfigCache = new RulesetConfigCache(SettingsStore));

osu.Game/Screens/Select/Carousel/DrawableCarouselBeatmap.cs

@@ -3,7 +3,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Threading;
 using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Colour;
@@ -41,6 +43,12 @@ namespace osu.Game.Screens.Select.Carousel
         [Resolved(CanBeNull = true)]
         private BeatmapSetOverlay beatmapOverlay { get; set; }
 
+        [Resolved]
+        private BeatmapDifficultyManager difficultyManager { get; set; }
+
+        private IBindable<StarDifficulty> starDifficultyBindable;
+        private CancellationTokenSource starDifficultyCancellationSource;
+
         public DrawableCarouselBeatmap(CarouselBeatmap panel)
             : base(panel)
         {
@@ -137,7 +145,6 @@ namespace osu.Game.Screens.Select.Carousel
                                         },
                                         starCounter = new StarCounter
                                         {
-                                            Current = (float)beatmap.StarDifficulty,
                                             Scale = new Vector2(0.8f),
                                         }
                                     }
@@ -181,6 +188,16 @@ namespace osu.Game.Screens.Select.Carousel
             if (Item.State.Value != CarouselItemState.Collapsed && Alpha == 0)
                 starCounter.ReplayAnimation();
 
+            starDifficultyCancellationSource?.Cancel();
+
+            // Only compute difficulty when the item is visible.
+            if (Item.State.Value != CarouselItemState.Collapsed)
+            {
+                // We've potentially cancelled the computation above so a new bindable is required.
+                starDifficultyBindable = difficultyManager.GetBindableDifficulty(beatmap, (starDifficultyCancellationSource = new CancellationTokenSource()).Token);
+                starDifficultyBindable.BindValueChanged(d => starCounter.Current = (float)d.NewValue.Stars, true);
+            }
+
             base.ApplyState();
         }
 
@@ -205,5 +222,11 @@ namespace osu.Game.Screens.Select.Carousel
                 return items.ToArray();
             }
         }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+            starDifficultyCancellationSource?.Cancel();
+        }
     }
 }

osu.Game/Screens/Select/Details/AdvancedStats.cs

@@ -14,10 +14,12 @@ using osu.Framework.Bindables;
 using System.Collections.Generic;
 using osu.Game.Rulesets.Mods;
 using System.Linq;
+using System.Threading;
 using osu.Framework.Threading;
 using osu.Framework.Utils;
 using osu.Game.Configuration;
 using osu.Game.Overlays.Settings;
+using osu.Game.Rulesets;
 
 namespace osu.Game.Screens.Select.Details
 {
@@ -26,6 +28,12 @@ namespace osu.Game.Screens.Select.Details
         [Resolved]
         private IBindable<IReadOnlyList<Mod>> mods { get; set; }
 
+        [Resolved]
+        private IBindable<RulesetInfo> ruleset { get; set; }
+
+        [Resolved]
+        private BeatmapDifficultyManager difficultyManager { get; set; }
+
         protected readonly StatisticRow FirstValue, HpDrain, Accuracy, ApproachRate;
         private readonly StatisticRow starDifficulty;
 
@@ -71,6 +79,7 @@ namespace osu.Game.Screens.Select.Details
         {
             base.LoadComplete();
 
+            ruleset.BindValueChanged(_ => updateStatistics());
             mods.BindValueChanged(modsChanged, true);
         }
 
@@ -132,11 +141,39 @@ namespace osu.Game.Screens.Select.Details
                     break;
             }
 
-            starDifficulty.Value = ((float)(Beatmap?.StarDifficulty ?? 0), null);
-
             HpDrain.Value = (baseDifficulty?.DrainRate ?? 0, adjustedDifficulty?.DrainRate);
             Accuracy.Value = (baseDifficulty?.OverallDifficulty ?? 0, adjustedDifficulty?.OverallDifficulty);
             ApproachRate.Value = (baseDifficulty?.ApproachRate ?? 0, adjustedDifficulty?.ApproachRate);
+
+            updateStarDifficulty();
+        }
+
+        private IBindable<StarDifficulty> normalStarDifficulty;
+        private IBindable<StarDifficulty> moddedStarDifficulty;
+        private CancellationTokenSource starDifficultyCancellationSource;
+
+        private void updateStarDifficulty()
+        {
+            starDifficultyCancellationSource?.Cancel();
+
+            if (Beatmap == null)
+                return;
+
+            starDifficultyCancellationSource = new CancellationTokenSource();
+
+            normalStarDifficulty = difficultyManager.GetBindableDifficulty(Beatmap, ruleset.Value, null, starDifficultyCancellationSource.Token);
+            moddedStarDifficulty = difficultyManager.GetBindableDifficulty(Beatmap, ruleset.Value, mods.Value, starDifficultyCancellationSource.Token);
+
+            normalStarDifficulty.BindValueChanged(_ => updateDisplay());
+            moddedStarDifficulty.BindValueChanged(_ => updateDisplay(), true);
+
+            void updateDisplay() => starDifficulty.Value = ((float)normalStarDifficulty.Value.Stars, (float)moddedStarDifficulty.Value.Stars);
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+            starDifficultyCancellationSource?.Cancel();
         }
 
         public class StatisticRow : Container, IHasAccentColour