Add LLaMA3 chat session example.

LLama.Examples/ExampleRunner.cs

@@ -5,6 +5,7 @@ public class ExampleRunner
 {
     private static readonly Dictionary<string, Func<Task>> Examples = new()
     {
+        { "Chat Session: LLama3", LLama3ChatSession.Run },
         { "Chat Session: History", ChatSessionWithHistory.Run },
         { "Chat Session: Role names", ChatSessionWithRoleName.Run },
         { "Chat Session: Role names stripped", ChatSessionStripRoleName.Run },

LLama.Examples/Examples/LLama3ChatSession.cs

@@ -0,0 +1,126 @@
+using LLama.Abstractions;
+using LLama.Common;
+
+namespace LLama.Examples.Examples;
+
+// When using chatsession, it's a common case that you want to strip the role names
+// rather than display them. This example shows how to use transforms to strip them.
+public class LLama3ChatSession
+{
+    public static async Task Run()
+    {
+        string modelPath = UserSettings.GetModelPath();
+
+        var parameters = new ModelParams(modelPath)
+        {
+            Seed = 1337,
+            GpuLayerCount = 10
+        };
+        using var model = LLamaWeights.LoadFromFile(parameters);
+        using var context = model.CreateContext(parameters);
+        var executor = new InteractiveExecutor(context);
+
+        var chatHistoryJson = File.ReadAllText("Assets/chat-with-bob.json");
+        ChatHistory chatHistory = ChatHistory.FromJson(chatHistoryJson) ?? new ChatHistory();
+
+        ChatSession session = new(executor, chatHistory);
+        session.WithHistoryTransform(new LLama3HistoryTransform());
+        session.WithOutputTransform(new LLamaTransforms.KeywordTextOutputStreamTransform(
+            new string[] { "User:", "Assistant:", "�" },
+            redundancyLength: 5));
+
+        InferenceParams inferenceParams = new InferenceParams()
+        {
+            Temperature = 0.6f,
+            AntiPrompts = new List<string> { "User:" }
+        };
+
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.WriteLine("The chat session has started.");
+
+        // show the prompt
+        Console.ForegroundColor = ConsoleColor.Green;
+        string userInput = Console.ReadLine() ?? "";
+
+        while (userInput != "exit")
+        {
+            await foreach (
+                var text
+                in session.ChatAsync(
+                    new ChatHistory.Message(AuthorRole.User, userInput),
+                    inferenceParams))
+            {
+                Console.ForegroundColor = ConsoleColor.White;
+                Console.Write(text);
+            }
+            Console.WriteLine();
+
+            Console.ForegroundColor = ConsoleColor.Green;
+            userInput = Console.ReadLine() ?? "";
+
+            Console.ForegroundColor = ConsoleColor.White;
+        }
+    }
+
+    class LLama3HistoryTransform : IHistoryTransform
+    {
+        /// <summary>
+        /// Convert a ChatHistory instance to plain text.
+        /// </summary>
+        /// <param name="history">The ChatHistory instance</param>
+        /// <returns></returns>
+        public string HistoryToText(ChatHistory history)
+        {
+            string res = Bos;
+            foreach (var message in history.Messages)
+            {
+                res += EncodeMessage(message);
+            }
+            res += EncodeHeader(new ChatHistory.Message(AuthorRole.Assistant, ""));
+            return res;
+        }
+
+        private string EncodeHeader(ChatHistory.Message message)
+        {
+            string res = StartHeaderId;
+            res += message.AuthorRole.ToString();
+            res += EndHeaderId;
+            res += "\n\n";
+            return res;
+        }
+
+        private string EncodeMessage(ChatHistory.Message message)
+        {
+            string res = EncodeHeader(message);
+            res += message.Content;
+            res += EndofTurn;
+            return res;
+        }
+
+        /// <summary>
+        /// Converts plain text to a ChatHistory instance.
+        /// </summary>
+        /// <param name="role">The role for the author.</param>
+        /// <param name="text">The chat history as plain text.</param>
+        /// <returns>The updated history.</returns>
+        public ChatHistory TextToHistory(AuthorRole role, string text)
+        {
+            return new ChatHistory(new ChatHistory.Message[] { new ChatHistory.Message(role, text) });
+        }
+
+        /// <summary>
+        /// Copy the transform.
+        /// </summary>
+        /// <returns></returns>
+        public IHistoryTransform Clone()
+        {
+            return new LLama3HistoryTransform();
+        }
+
+        private const string StartHeaderId = "<|start_header_id|>";
+        private const string EndHeaderId = "<|end_header_id|>";
+        private const string Bos = "<|begin_of_text|>";
+        private const string Eos = "<|end_of_text|>";
+        private const string EndofTurn = "<|eot_id|>";
+    }
+}

LLama/LLamaTransforms.cs

@@ -235,15 +235,19 @@ public async IAsyncEnumerable<string> TransformAsync(IAsyncEnumerable<string> to
                     var current = string.Join("", window);
                     if (_keywords.Any(x => current.Contains(x)))
                     {
-                        var matchedKeyword = _keywords.First(x => current.Contains(x));
+                        var matchedKeywords = _keywords.Where(x => current.Contains(x));
                         int total = window.Count;
                         for (int i = 0; i < total; i++)
                         {
                             window.Dequeue();
                         }
                         if (!_removeAllMatchedTokens)
                         {
-                            yield return current.Replace(matchedKeyword, "");
+                            foreach(var keyword in matchedKeywords)
+                            {
+                                current = current.Replace(keyword, "");
+                            }
+                            yield return current;
                         }
                     }
                     if (current.Length >= _maxKeywordLength)