perf: message serializations

Author: lucasteles

benchmarks/Backdash.Benchmarks.Ping/PingMessageHandler.cs

@@ -9,11 +9,7 @@ sealed class PingMessageHandler(IPeerClient<PingMessage> sender) : IPeerObserver
     public static long TotalProcessed => processedCount;
     static long processedCount;
 
-    public void OnPeerMessage(
-        in PingMessage message,
-        SocketAddress from,
-        int bytesReceived
-    )
+    public void OnPeerMessage(ref readonly PingMessage message, in SocketAddress from, int bytesReceived)
     {
         Interlocked.Increment(ref processedCount);
 

benchmarks/Backdash.Benchmarks/Network/Message.cs

@@ -19,7 +19,7 @@ sealed class PingMessageHandler(string name, IPeerClient<PingMessage> sender) :
     public long BadMessages => badMessages;
     public event Action<long> OnProcessed = delegate { };
 
-    public void OnPeerMessage(in PingMessage message, SocketAddress from, int bytesReceived
+    public void OnPeerMessage(ref readonly PingMessage message, in SocketAddress from, int bytesReceived
     )
     {
         Interlocked.Increment(ref processedCount);

samples/SpaceWar.Shared/Logic/GameState.cs

@@ -1,4 +1,4 @@
-using Backdash.Data;
+using Backdash;
 using Backdash.Serialization;
 
 namespace SpaceWar.Logic;
@@ -13,8 +13,7 @@ public sealed record GameState
     public void Init(int numberOfPlayers)
     {
         Ships = new Ship[numberOfPlayers];
-        for (var i = 0; i < numberOfPlayers; i++)
-            Ships[i] = new();
+        for (var i = 0; i < numberOfPlayers; i++) Ships[i] = new();
         FrameNumber = 0;
         Bounds = Config.InternalBounds;
         Bounds.Inflate(-Config.WindowPadding, -Config.WindowPadding);

src/Backdash/Backends/LocalBackend.cs

@@ -3,6 +3,7 @@
 using Backdash.Network;
 using Backdash.Synchronizing.Input;
 using Backdash.Synchronizing.Random;
+using Backdash.Synchronizing.State;
 
 namespace Backdash.Backends;
 
@@ -55,6 +56,7 @@ public LocalBackend(NetcodeOptions options, BackendServices<TInput> services)
     public SessionMode Mode => SessionMode.Local;
     public FrameSpan FramesBehind => synchronizer.FramesBehind;
     public FrameSpan RollbackFrames => synchronizer.RollbackFrames;
+    public SavedFrame CurrentSavedFrame => synchronizer.GetLastSavedFrame();
 
     public IReadOnlyCollection<PlayerHandle> GetPlayers() => addedPlayers;
 

src/Backdash/Backends/RemoteBackend.cs

@@ -11,6 +11,7 @@
 using Backdash.Synchronizing.Input;
 using Backdash.Synchronizing.Input.Confirmed;
 using Backdash.Synchronizing.Random;
+using Backdash.Synchronizing.State;
 
 namespace Backdash.Backends;
 
@@ -68,10 +69,10 @@ BackendServices<TInput> services
         logger = services.Logger;
         inputListener = services.InputListener;
         Random = services.DeterministicRandom;
-        syncNumber = services.Random.MagicNumber();
         inputComparer = services.InputComparer;
-        inputGroupComparer = ConfirmedInputComparer<TInput>.Create(services.InputComparer);
 
+        inputGroupComparer = ConfirmedInputComparer<TInput>.Create(services.InputComparer);
+        syncNumber = services.Random.MagicNumber();
         peerInputEventQueue = new();
         peerCombinedInputsEventPublisher = new ProtocolCombinedInputsEventPublisher<TInput>(peerInputEventQueue);
         inputGroupSerializer = new ConfirmedInputsSerializer<TInput>(inputSerializer);
@@ -140,6 +141,7 @@ public void Close()
     public Frame CurrentFrame => synchronizer.CurrentFrame;
     public FrameSpan RollbackFrames => synchronizer.RollbackFrames;
     public FrameSpan FramesBehind => synchronizer.FramesBehind;
+    public SavedFrame CurrentSavedFrame => synchronizer.GetLastSavedFrame();
     public int NumberOfPlayers => addedPlayers.Count;
 
     public int NumberOfSpectators => addedSpectators.Count;

src/Backdash/Backends/ReplayBackend.cs

@@ -9,13 +9,11 @@
 
 namespace Backdash.Backends;
 
-sealed class ReplayBackend<TInput> : INetcodeSession<TInput>
-    where TInput : unmanaged
+sealed class ReplayBackend<TInput> : INetcodeSession<TInput> where TInput : unmanaged
 {
     readonly Logger logger;
     readonly PlayerHandle[] fakePlayers;
     INetcodeSessionHandler callbacks;
-    readonly IDeterministicRandom deterministicRandom;
     bool isSynchronizing = true;
     SynchronizedInput<TInput>[] syncInputBuffer = [];
     TInput[] inputBuffer = [];
@@ -43,12 +41,12 @@ public ReplayBackend(int numberOfPlayers,
         logger = services.Logger;
         stateStore = services.StateStore;
         checksumProvider = services.ChecksumProvider;
-        deterministicRandom = services.DeterministicRandom;
+        Random = services.DeterministicRandom;
         NumberOfPlayers = numberOfPlayers;
-        fakePlayers = Enumerable.Range(0, numberOfPlayers)
-            .Select(x => new PlayerHandle(PlayerType.Remote, x + 1, x)).ToArray();
-
         callbacks = new EmptySessionHandler(logger);
+        fakePlayers = Enumerable.Range(0, numberOfPlayers)
+            .Select(x => new PlayerHandle(PlayerType.Remote, x + 1, x))
+            .ToArray();
 
         stateStore.Initialize(controls.MaxBackwardFrames);
     }
@@ -72,9 +70,13 @@ public void Close()
     public Frame CurrentFrame { get; private set; } = Frame.Zero;
     public FrameSpan RollbackFrames => FrameSpan.Zero;
     public FrameSpan FramesBehind => FrameSpan.Zero;
-    public int NumberOfPlayers { get; private set; }
+
+    public SavedFrame CurrentSavedFrame => stateStore.GetCurrent();
+
     public int NumberOfSpectators => 0;
-    public IDeterministicRandom Random => deterministicRandom;
+    public int NumberOfPlayers { get; private set; }
+    public IDeterministicRandom Random { get; }
+
     public SessionMode Mode => SessionMode.Replaying;
     public void DisconnectPlayer(in PlayerHandle player) { }
     public ResultCode AddLocalInput(PlayerHandle player, in TInput localInput) => ResultCode.Ok;
@@ -155,7 +157,7 @@ public ResultCode SynchronizeInputs()
         }
 
         var inputPopCount = useInputSeedForRandom ? Mem.PopCount<TInput>(inputBuffer.AsSpan()) : 0;
-        deterministicRandom.UpdateSeed(CurrentFrame.Number, inputPopCount);
+        Random.UpdateSeed(CurrentFrame.Number, inputPopCount);
 
         return ResultCode.Ok;
     }
@@ -190,7 +192,6 @@ public void LoadFrame(in Frame frame)
             var offset = 0;
             BinaryBufferReader reader = new(savedFrame.GameState.WrittenSpan, ref offset);
             callbacks.LoadState(in frame, in reader);
-
             CurrentFrame = savedFrame.Frame;
         }
         catch (NetcodeException)

src/Backdash/Backends/SpectatorBackend.cs

@@ -9,6 +9,7 @@
 using Backdash.Synchronizing.Input;
 using Backdash.Synchronizing.Input.Confirmed;
 using Backdash.Synchronizing.Random;
+using Backdash.Synchronizing.State;
 
 namespace Backdash.Backends;
 
@@ -24,7 +25,6 @@ sealed class SpectatorBackend<TInput> :
     readonly NetcodeOptions options;
     readonly IBackgroundJobManager backgroundJobManager;
     readonly IClock clock;
-    readonly IDeterministicRandom deterministicRandom;
     readonly ConnectionsState localConnections = new(0);
     readonly GameInput<ConfirmedInputs<TInput>>[] inputs;
     readonly PeerConnection<ConfirmedInputs<TInput>> host;
@@ -38,6 +38,8 @@ sealed class SpectatorBackend<TInput> :
     SynchronizedInput<TInput>[] syncInputBuffer = [];
     TInput[] inputBuffer = [];
     bool closed;
+    readonly IStateStore stateStore;
+    readonly IChecksumProvider checksumProvider;
 
     public SpectatorBackend(int port,
         IPEndPoint hostEndpoint,
@@ -53,9 +55,11 @@ public SpectatorBackend(int port,
         this.hostEndpoint = hostEndpoint;
         this.options = options;
         backgroundJobManager = services.JobManager;
-        deterministicRandom = services.DeterministicRandom;
+        Random = services.DeterministicRandom;
         logger = services.Logger;
         clock = services.Clock;
+        stateStore = services.StateStore;
+        checksumProvider = services.ChecksumProvider;
         NumberOfPlayers = numberOfPlayers;
         fakePlayers = Enumerable.Range(0, numberOfPlayers)
             .Select(x => new PlayerHandle(PlayerType.Remote, x + 1, x)).ToArray();
@@ -71,17 +75,19 @@ public SpectatorBackend(int port,
 
         PeerConnectionFactory peerConnectionFactory = new(
             this, clock, services.Random, logger, udp,
-            options.Protocol, options.TimeSync, services.StateStore
+            options.Protocol, options.TimeSync, stateStore
         );
 
         ProtocolState protocolState =
             new(new(PlayerType.Remote, 0), hostEndpoint, localConnections, magicNumber);
 
         var inputGroupComparer = ConfirmedInputComparer<TInput>.Create(services.InputComparer);
         host = peerConnectionFactory.Create(protocolState, inputGroupSerializer, this, inputGroupComparer);
+
         peerObservers.Add(host.GetUdpObserver());
         host.Synchronize();
         isSynchronizing = true;
+        stateStore.Initialize(options.TotalPredictionFrames);
     }
 
     public void Dispose()
@@ -106,11 +112,14 @@ public void Close()
     public Frame CurrentFrame { get; private set; } = Frame.Zero;
     public FrameSpan RollbackFrames => FrameSpan.Zero;
     public FrameSpan FramesBehind => FrameSpan.Zero;
+    public SavedFrame CurrentSavedFrame => stateStore.GetCurrent();
+
     public int NumberOfPlayers { get; private set; }
     public int NumberOfSpectators => 0;
 
-    public IDeterministicRandom Random => deterministicRandom;
+    public IDeterministicRandom Random { get; }
     public SessionMode Mode => SessionMode.Spectating;
+
     public void DisconnectPlayer(in PlayerHandle player) { }
     public ResultCode AddLocalInput(PlayerHandle player, in TInput localInput) => ResultCode.Ok;
     public IReadOnlyCollection<PlayerHandle> GetPlayers() => fakePlayers;
@@ -124,8 +133,8 @@ public void BeginFrame()
         if (isSynchronizing)
             return;
 
-        if (lastReceivedInputTime > 0
-            && clock.GetElapsedTime(lastReceivedInputTime) > options.Protocol.DisconnectTimeout)
+        if (lastReceivedInputTime > 0 &&
+            clock.GetElapsedTime(lastReceivedInputTime) > options.Protocol.DisconnectTimeout)
             Close();
     }
 
@@ -243,12 +252,27 @@ public ResultCode SynchronizeInputs()
         }
 
         var inputPopCount = options.UseInputSeedForRandom ? Mem.PopCount<TInput>(inputBuffer.AsSpan()) : 0;
-        deterministicRandom.UpdateSeed(CurrentFrame.Number, inputPopCount);
+        Random.UpdateSeed(CurrentFrame.Number, inputPopCount);
 
         CurrentFrame++;
+        SaveCurrentFrame();
         return ResultCode.Ok;
     }
 
+    void SaveCurrentFrame()
+    {
+        var currentFrame = CurrentFrame;
+        ref var nextState = ref stateStore.GetCurrent();
+
+        BinaryBufferWriter writer = new(nextState.GameState);
+        callbacks.SaveState(in currentFrame, in writer);
+        nextState.Frame = currentFrame;
+        nextState.Checksum = checksumProvider.Compute(nextState.GameState.WrittenSpan);
+
+        stateStore.Advance();
+        logger.Write(LogLevel.Trace, $"spectator: saved frame {nextState.Frame} (checksum: {nextState.Checksum}).");
+    }
+
     public ref readonly SynchronizedInput<TInput> GetInput(int index) =>
         ref syncInputBuffer[index];
 
@@ -257,12 +281,12 @@ public ref readonly SynchronizedInput<TInput> GetInput(in PlayerHandle player) =
 
     public void GetInputs(Span<SynchronizedInput<TInput>> buffer) => syncInputBuffer.CopyTo(buffer);
 
-    void IProtocolInputEventPublisher<ConfirmedInputs<TInput>>.Publish(in GameInputEvent<ConfirmedInputs<TInput>> evt)
+    bool IProtocolInputEventPublisher<ConfirmedInputs<TInput>>.Publish(in GameInputEvent<ConfirmedInputs<TInput>> evt)
     {
         lastReceivedInputTime = clock.GetTimeStamp();
         var (_, input) = evt;
         inputs[input.Frame.Number % inputs.Length] = input;
         host.SetLocalFrameNumber(input.Frame, options.FramesPerSecond);
-        host.SendInputAck();
+        return host.SendInputAck();
     }
 }

src/Backdash/Backends/SyncTestBackend.cs

@@ -82,6 +82,7 @@ public SyncTestBackend(NetcodeOptions options,
     public SessionMode Mode => SessionMode.SyncTest;
     public FrameSpan FramesBehind => synchronizer.FramesBehind;
     public FrameSpan RollbackFrames => synchronizer.RollbackFrames;
+    public SavedFrame CurrentSavedFrame => synchronizer.GetLastSavedFrame();
 
     public IReadOnlyCollection<PlayerHandle> GetPlayers() =>
         addedPlayers.Count is 0 ? [new(PlayerType.Local, 1, 0)] : addedPlayers;

src/Backdash/Core/MathI.cs

@@ -0,0 +1,15 @@
+using System.Runtime.CompilerServices;
+
+namespace Backdash;
+
+/// <summary>
+/// Int Math
+/// </summary>
+public static class MathI
+{
+    /// <summary>
+    ///  Divide two integers ceiling the result
+    /// </summary>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static int CeilDiv(int x, int y) => x is 0 ? 0 : 1 + ((x - 1) / y);
+}

src/Backdash/Data/ByteSize.cs

@@ -226,6 +226,11 @@ static ReadOnlySpan<char> FindSymbol(ReadOnlySpan<char> str)
         return [];
     }
 
+    /// <summary>
+    /// Returns number of bits for <paramref name="byteCount"/> bytes.
+    /// </summary>
+    public static int ByteCountOfBits(in ushort byteCount) => MathI.CeilDiv(byteCount, ByteToBits);
+
     /// <inheritdoc />
     public static bool operator >(ByteSize left, ByteSize right) => left.ByteCount > right.ByteCount;