Improved performance with hot-path optimization.

Author: electricessence

Trie/Open.Collections.Trie.csproj

@@ -18,7 +18,7 @@
 		<PackageProjectUrl>https://github.com/Open-NET-Libraries/Open.Collections/tree/master/Trie</PackageProjectUrl>
 		<RepositoryUrl>https://github.com/Open-NET-Libraries/Open.Collections/</RepositoryUrl>
 		<RepositoryType>git</RepositoryType>
-		<Version>1.1.0</Version>
+		<Version>1.1.1</Version>
 		<PackageReleaseNotes></PackageReleaseNotes>
 		<PackageLicenseExpression>MIT</PackageLicenseExpression>
 		<PublishRepositoryUrl>true</PublishRepositoryUrl>

Trie/TrieBase.cs

@@ -221,6 +221,10 @@ internal abstract class NodeBase : ITrieNode<TKey, TValue>
 
         private (bool isSet, TValue? value) _value;
 
+        // It's not uncommon to have a 'hot path' that will be requested frequently.
+        // This facilitates that by caching the last child that was requested.
+        private (bool exists, TKey key, ITrieNode<TKey, TValue> child) _recentChild;
+
         public bool IsSet => _value.isSet;
 
         internal TValue GetValueOrThrow()
@@ -261,7 +265,16 @@ public bool TryGetChild(TKey key, out ITrieNode<TKey, TValue> child)
                 return false;
             }
 
-            return Children!.TryGetValue(key, out child);
+            var recent = _recentChild;
+            if(recent.exists && recent.key!.Equals(key))
+            {
+                child = recent.child;
+                return true;
+            }
+
+            bool found = Children!.TryGetValue(key, out child);
+            _recentChild = (true, key, child);
+            return found;
         }
 
         public ITrieNode<TKey, TValue> GetChild(TKey key)

benchmarking/Benchmarks/TrieBenchmarks.cs

@@ -28,7 +28,7 @@ public class TrieBenchmark
 
     private Trie<string, int> trie;
     private Dictionary<string, int> dictionary;
-    private List<(string[], string)> keys;
+    private (string[], string)[] keys;
 
     [GlobalSetup]
     public void GlobalSetup()
@@ -38,20 +38,19 @@ public void GlobalSetup()
         dictionary = new();
         ctrie = new();
         cdictionary = new();
-        keys = new();
-
-        foreach (string[] key in GenerateTree(Depth, NodeSize))
-        {
-            x++;
-            trie.Add(key, x);
-            ctrie.Add(key, x);
+        keys = GenerateTree(Depth, NodeSize)
+            .Select(key=>
+            {
+                x++;
+                trie.Add(key, x);
+                ctrie.Add(key, x);
 
-            string keyString = string.Join('/', key);
-            dictionary.Add(keyString, x);
-            cdictionary.TryAdd(keyString, x);
+                string keyString = string.Join('/', key);
+                dictionary.Add(keyString, x);
+                cdictionary.TryAdd(keyString, x);
 
-            keys.Add((key, keyString));
-        }
+                return (key, keyString);
+            }).ToArray();
     }
 
     public static IEnumerable<string[]> GenerateTree(int depth, int nodeCount, Stack<string> stack = null)
@@ -79,7 +78,7 @@ public static IEnumerable<string[]> GenerateTree(int depth, int nodeCount, Stack
     public int TrieLookup()
     {
         int result = 0;
-        foreach(var key in keys)
+        foreach(var key in keys.AsSpan())
         {
             trie.TryGetValue(key.Item1, out result);
         }
@@ -90,7 +89,7 @@ public int TrieLookup()
     public int TrieWalkLookup()
     {
         int result = 0;
-        foreach (var key in keys)
+        foreach (var key in keys.AsSpan())
         {
             string[] k = key.Item1;
             result = trie.GetChild(k[0]).GetChild(k[1]).GetChild(k[2]).GetChild(k[3]).Value;
@@ -102,7 +101,7 @@ public int TrieWalkLookup()
     public int TrieLookupWithToArray()
     {
         int result = 0;
-        foreach (var key in keys)
+        foreach (var key in keys.AsSpan())
         {
             trie.TryGetValue(key.Item1.ToArray(), out result);
         }
@@ -113,7 +112,7 @@ public int TrieLookupWithToArray()
     public int DictionaryLookup()
     {
         int result = 0;
-        foreach (var key in keys)
+        foreach (var key in keys.AsSpan())
         {
             result = dictionary[key.Item2];
 
@@ -125,7 +124,7 @@ public int DictionaryLookup()
     public int DictionaryLookupKeyConcat()
     {
         int result = 0;
-        foreach (var key in keys)
+        foreach (var key in keys.AsSpan())
         {
             string[] k = key.Item1;
             result = dictionary[$"{k[0]}/{k[1]}/{k[2]}/{k[3]}"];
@@ -137,7 +136,7 @@ public int DictionaryLookupKeyConcat()
     public int DictionaryLookupWithJoin()
     {
         int result = 0;
-        foreach (var key in keys)
+        foreach (var key in keys.AsSpan())
         {
             result = dictionary[string.Join("/", key.Item1)];
         }