01 - Optimize position table - part 1

src/DotNetPerf.Domain/Outrights/Calculator.cs

@@ -45,6 +45,8 @@ private static TablePositionHistory Simulate(int simulations, IEnumerable<Team>
                 match.Reset();
             }
 
+            table.Sort();
+
             tablePositionHistory.Update(table);
 
             table.Reset();

src/DotNetPerf.Domain/Outrights/Position.cs

@@ -2,23 +2,31 @@
 
 namespace DotNetPerf.Domain.Outrights;
 
-public sealed record Position : IComparable<Position>
+public record struct Position : IComparable<Position>
 {
     public Position(Team team)
     {
         Team = team;
+        Played = 0;
+        Won = 0;
+        Drawn = 0;
+        Lost = 0;
+        GoalsFor = 0;
+        GoalsAgainst = 0;
+        GoalDifference = 0;
+        Points = 0;
     }
 
-    public Team Team { get; }
+    public readonly Team Team { get; }
 
-    public int Played { get; private set; }
-    public int Won { get; private set; }
-    public int Drawn { get; private set; }
-    public int Lost { get; private set; }
-    public int GoalsFor { get; private set; }
-    public int GoalsAgainst { get; private set; }
-    public int GoalDifference { get; private set; }
-    public int Points { get; private set; }
+    public int Played { readonly get; private set; }
+    public int Won { readonly get; private set; }
+    public int Drawn { readonly get; private set; }
+    public int Lost { readonly get; private set; }
+    public int GoalsFor { readonly get; private set; }
+    public int GoalsAgainst { readonly get; private set; }
+    public int GoalDifference { readonly get; private set; }
+    public int Points { readonly get; private set; }
 
     public void AddMatch(Match match)
     {
@@ -64,11 +72,10 @@ public void Reset()
         Points = 0;
     }
 
-    public int CompareTo(Position? other)
+    public int CompareTo(Position other)
     {
         return other switch
         {
-            null => -1,
             var p when Points == p.Points => (GoalDifference - p.GoalDifference) switch
             {
                 0 => 0,

src/DotNetPerf.Domain/Outrights/Table.cs

@@ -2,35 +2,59 @@
 
 public sealed record Table
 {
-    private readonly List<Position> _positions;
+    private readonly Position[] _positions;
+    private readonly Dictionary<Team, int> _map;
 
-    public int Count => _positions.Count;
+    public int Count => _positions.Length;
 
-    public Position this[int index] => _positions[index];
+    public ref readonly Position this[int index] => ref _positions[index];
 
     public Table(IEnumerable<Team> teams)
     {
-        _positions = new (teams.Count());
+        _positions = new Position[teams.Count()];
+        _map = new(teams.Count());
+        var positionIndex = 0;
         foreach (var team in teams)
-            _positions.Add(new Position(team));
+        {
+            _positions[positionIndex] = new Position(team);
+            _map[team] = positionIndex++;
+        }
     }
 
     public void AddResult(Match match)
     {
-        var homePosition = _positions.Single(p => p?.Team == match.HomeTeam);
-        var awayPosition = _positions.Single(p => p?.Team == match.AwayTeam);
+        var positions = _positions;
+
+        ref var homePosition = ref positions[_map[match.HomeTeam]];
+        ref var awayPosition = ref positions[_map[match.AwayTeam]];
 
         homePosition.AddMatch(match);
         awayPosition.AddMatch(match);
+    }
 
-        _positions.Sort();
+    public void Sort()
+    {
+        Span<Position> positions = _positions;
+
+        positions.Sort();
+        for (int i = 0; i < positions.Length; i++)
+        {
+            ref readonly var position = ref positions[i];
+            _map[position.Team] = i;
+        }
     }
 
-    public List<Position>.Enumerator GetEnumerator() => _positions.GetEnumerator();
+    public ReadOnlySpan<Position>.Enumerator GetEnumerator()
+    {
+        ReadOnlySpan<Position> positions = _positions;
+        return positions.GetEnumerator();
+    }
 
     public void Reset()
     {
-        foreach (var position in _positions)
+        Span<Position> positions = _positions;
+
+        foreach (ref var position in positions)
             position.Reset();
     }
 }

src/DotNetPerf.Domain/Outrights/TablePositionHistory.cs

@@ -19,7 +19,7 @@ public void Update(Table table)
     {
         for (int i = 0; i < table.Count; i++)
         {
-            var position = table[i];
+            ref readonly var position = ref table[i];
             _map[position.Team][i]++;
         }
     }

tests/DotNetPerf.Benchmarks/Outrights/Outrights.cs

@@ -14,7 +14,7 @@ namespace DotNetPerf.Benchmarks.Outrights;
 [MemoryDiagnoser]
 [DisassemblyDiagnoser(maxDepth: 3)]
 //[EtwProfiler]
-[EventPipeProfiler(EventPipeProfile.CpuSampling)]
+//[EventPipeProfiler(EventPipeProfile.CpuSampling)]
 public class Outrights
 {
     private CalculateOutrights _input;

tests/DotNetPerf.Benchmarks/Outrights/README.md

@@ -14,14 +14,14 @@ AMD Ryzen 5 5600X, 1 CPU, 12 logical and 6 physical cores
 
 
 ```
-|    Method | Simulations |     Mean |   Error |  StdDev |     Gen 0 | Code Size | Allocated |
-|---------- |------------ |---------:|--------:|--------:|----------:|----------:|----------:|
-| Calculate |        1000 | 299.4 ms | 5.85 ms | 5.75 ms | 5000.0000 |      0 MB |     84 MB |
+|    Method | Simulations |     Mean |    Error |   StdDev | Code Size | Allocated |
+|---------- |------------ |---------:|---------:|---------:|----------:|----------:|
+| Calculate |        1000 | 47.85 ms | 0.400 ms | 0.374 ms |      8 KB |     82 KB |
 
 
 #### Visual Studio 2022 profiler
 
-![Visual Studio 2022 profiler](/imgs/visual-studio-profiler.png)
+![Visual Studio 2022 profiler](/imgs/visual-studio-profiler-01.png)
 
 #### Other tools