feat: support save and load chat session.

LLama.Examples/Program.cs

@@ -28,7 +28,7 @@ if(version == 1)
     var prompt = File.ReadAllText("Assets/chat-with-bob.txt").Trim();
     //string prompt = " Qeustion: how to do binary search for an array in C#? Answer: ";
 
-    InteractiveExecutor ex = new(new LLamaModel(new ModelParams(modelPath, contextSize: 1024, seed: 1337)));
+    InteractiveExecutor ex = new(new LLamaModel(new ModelParams(modelPath, contextSize: 1024, seed: 1337, gpuLayerCount: 5)));
 
     ChatSession session = new ChatSession(ex).WithOutputTransform(new LLamaTransforms.KeywordTextOutputStreamTransform(new string[] { "User:", "Bob:" }));
 
@@ -39,6 +39,17 @@ if(version == 1)
             Console.Write(text);
         }
         prompt = Console.ReadLine();
+        if(prompt == "save")
+        {
+            session.SaveSession("./SessionState");
+            Console.WriteLine("Saved session!");
+            ex.Model.Dispose();
+            ex = new(new LLamaModel(new ModelParams(modelPath, contextSize: 1024, seed: 1337, gpuLayerCount: 5)));
+            session = new ChatSession(ex).WithOutputTransform(new LLamaTransforms.KeywordTextOutputStreamTransform(new string[] { "User:", "Bob:" }));
+            session.LoadSession("./SessionState");
+            Console.WriteLine("Loaded session!");
+            prompt = Console.ReadLine();
+        }
     }
 
     ex.Model.Dispose();

LLama/ChatSession.cs

@@ -1,5 +1,6 @@
 using LLama.Common;
 using System.Collections.Generic;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading;
@@ -10,6 +11,8 @@ namespace LLama
     {
         private ILLamaExecutor _executor;
         private ChatHistory _history;
+        private static readonly string _executorStateFilename = "ExecutorState.json";
+        private static readonly string _modelStateFilename = "ModelState.st";
         public ILLamaExecutor Executor => _executor;
         public ChatHistory History => _history;
         public SessionParams Params { get; set; }
@@ -42,6 +45,56 @@ namespace LLama
             return this;
         }
 
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="path">The directory name to save the session. If the directory does not exist, a new directory will be created.</param>
+        public virtual void SaveSession(string path)
+        {
+            if (!Directory.Exists(path))
+            {
+                Directory.CreateDirectory(path);
+            }
+            _executor.Model.SaveState(Path.Combine(path, _modelStateFilename));
+            if(Executor is StatelessExecutor)
+            {
+
+            }
+            else if(Executor is StatefulExecutorBase statefulExecutor)
+            {
+                statefulExecutor.SaveState(Path.Combine(path, _executorStateFilename));
+            }
+            else
+            {
+                throw new System.NotImplementedException("You're using a customized executor. Please inherit ChatSession and rewrite the method.");
+            }
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="path">The directory name to load the session.</param>
+        public virtual void LoadSession(string path)
+        {
+            if (!Directory.Exists(path))
+            {
+                throw new FileNotFoundException($"Directory {path} does not exist.");
+            }
+            _executor.Model.LoadState(Path.Combine(path, _modelStateFilename));
+            if (Executor is StatelessExecutor)
+            {
+
+            }
+            else if (Executor is StatefulExecutorBase statefulExecutor)
+            {
+                statefulExecutor.LoadState(Path.Combine(path, _executorStateFilename));
+            }
+            else
+            {
+                throw new System.NotImplementedException("You're using a customized executor. Please inherit ChatSession and rewrite the method.");
+            }
+        }
+
         /// <summary>
         /// Get the response from the LLama model with chat histories.
         /// </summary>

LLama/LLamaExecutorBase.cs

@@ -12,7 +12,7 @@ using System.Threading;
 namespace LLama
 {
     using llama_token = Int32;
-    public abstract class ChatExecutorBase : ILLamaExecutor
+    public abstract class StatefulExecutorBase : ILLamaExecutor
     {
         protected readonly LLamaModel _model;
         protected ILLamaLogger? _logger;
@@ -26,7 +26,7 @@ namespace LLama
         protected List<llama_token> _session_tokens = new();
         protected FixedSizeQuene<llama_token> _last_n_tokens;
         public LLamaModel Model => _model;
-        protected ChatExecutorBase(LLamaModel model, ILLamaLogger? logger = null)
+        protected StatefulExecutorBase(LLamaModel model, ILLamaLogger? logger = null)
         {
             _model = model;
             _logger = logger;
@@ -38,7 +38,7 @@ namespace LLama
             _last_n_tokens = new FixedSizeQuene<llama_token>(_model.ContextSize).FillWith(0);
         }
 
-        public unsafe ChatExecutorBase WithSessionFile(string filename)
+        public unsafe StatefulExecutorBase WithSessionFile(string filename)
         {
             _pathSession = filename;
             if (string.IsNullOrEmpty(filename))

LLama/LLamaInstructExecutor.cs

@@ -11,7 +11,7 @@ using System.Text.Json.Serialization;
 namespace LLama
 {
     using llama_token = Int32;
-    public class InstructExecutor : ChatExecutorBase
+    public class InstructExecutor : StatefulExecutorBase
     {
         bool _is_prompt_run = true;
         llama_token[] _inp_pfx;

LLama/LLamaInteractExecutor.cs

@@ -14,7 +14,7 @@ using System.Threading.Tasks;
 namespace LLama
 {
     using llama_token = Int32;
-    public class InteractiveExecutor : ChatExecutorBase
+    public class InteractiveExecutor : StatefulExecutorBase
     {
         bool _is_prompt_run = true;
         llama_token[] _llama_token_newline;