- Added LLamaTemplate which efficiently formats a series of message…

…s according to the model template.

 - Fixed `llama_chat_apply_template` method (wrong entrypoint, couldn't handle null model)

LLama.Unittest/TemplateTests.cs

@@ -0,0 +1,245 @@
+using System.Text;
+using LLama.Common;
+using LLama.Native;
+
+namespace LLama.Unittest;
+
+public sealed class TemplateTests
+    : IDisposable
+{
+    private readonly LLamaWeights _model;
+
+    public TemplateTests()
+    {
+        var @params = new ModelParams(Constants.GenerativeModelPath)
+        {
+            ContextSize = 1,
+            GpuLayerCount = Constants.CIGpuLayerCount
+        };
+        _model = LLamaWeights.LoadFromFile(@params);
+    }
+
+    public void Dispose()
+    {
+        _model.Dispose();
+    }
+
+    [Fact]
+    public void BasicTemplate()
+    {
+        var templater = new LLamaTemplate(_model);
+
+        Assert.Equal(0, templater.Count);
+        templater.Add("assistant", "hello");
+        Assert.Equal(1, templater.Count);
+        templater.Add("user", "world");
+        Assert.Equal(2, templater.Count);
+        templater.Add("assistant", "111");
+        Assert.Equal(3, templater.Count);
+        templater.Add("user", "aaa");
+        Assert.Equal(4, templater.Count);
+        templater.Add("assistant", "222");
+        Assert.Equal(5, templater.Count);
+        templater.Add("user", "bbb");
+        Assert.Equal(6, templater.Count);
+        templater.Add("assistant", "333");
+        Assert.Equal(7, templater.Count);
+        templater.Add("user", "ccc");
+        Assert.Equal(8, templater.Count);
+
+        // Call once with empty array to discover length
+        var length = templater.Apply(Array.Empty<byte>());
+        var dest = new byte[length];
+
+        Assert.Equal(8, templater.Count);
+
+        // Call again to get contents
+        length = templater.Apply(dest);
+
+        Assert.Equal(8, templater.Count);
+
+        var templateResult = Encoding.UTF8.GetString(dest.AsSpan(0, length));
+        const string expected = "<|im_start|>assistant\nhello<|im_end|>\n" +
+                                "<|im_start|>user\nworld<|im_end|>\n" +
+                                "<|im_start|>assistant\n" +
+                                "111<|im_end|>" +
+                                "\n<|im_start|>user\n" +
+                                "aaa<|im_end|>\n" +
+                                "<|im_start|>assistant\n" +
+                                "222<|im_end|>\n" +
+                                "<|im_start|>user\n" +
+                                "bbb<|im_end|>\n" +
+                                "<|im_start|>assistant\n" +
+                                "333<|im_end|>\n" +
+                                "<|im_start|>user\n" +
+                                "ccc<|im_end|>\n";
+
+        Assert.Equal(expected, templateResult);
+    }
+
+    [Fact]
+    public void CustomTemplate()
+    {
+        var templater = new LLamaTemplate("gemma");
+
+        Assert.Equal(0, templater.Count);
+        templater.Add("assistant", "hello");
+        Assert.Equal(1, templater.Count);
+        templater.Add("user", "world");
+        Assert.Equal(2, templater.Count);
+        templater.Add("assistant", "111");
+        Assert.Equal(3, templater.Count);
+        templater.Add("user", "aaa");
+        Assert.Equal(4, templater.Count);
+
+        // Call once with empty array to discover length
+        var length = templater.Apply(Array.Empty<byte>());
+        var dest = new byte[length];
+
+        Assert.Equal(4, templater.Count);
+
+        // Call again to get contents
+        length = templater.Apply(dest);
+
+        Assert.Equal(4, templater.Count);
+
+        var templateResult = Encoding.UTF8.GetString(dest.AsSpan(0, length));
+        const string expected = "<start_of_turn>model\n" +
+                                "hello<end_of_turn>\n" +
+                                "<start_of_turn>user\n" +
+                                "world<end_of_turn>\n" +
+                                "<start_of_turn>model\n" +
+                                "111<end_of_turn>\n" +
+                                "<start_of_turn>user\n" +
+                                "aaa<end_of_turn>\n";
+
+        Assert.Equal(expected, templateResult);
+    }
+
+    [Fact]
+    public void BasicTemplateWithAddAssistant()
+    {
+        var templater = new LLamaTemplate(_model)
+        {
+            AddAssistant = true,
+        };
+
+        Assert.Equal(0, templater.Count);
+        templater.Add("assistant", "hello");
+        Assert.Equal(1, templater.Count);
+        templater.Add("user", "world");
+        Assert.Equal(2, templater.Count);
+        templater.Add("assistant", "111");
+        Assert.Equal(3, templater.Count);
+        templater.Add("user", "aaa");
+        Assert.Equal(4, templater.Count);
+        templater.Add("assistant", "222");
+        Assert.Equal(5, templater.Count);
+        templater.Add("user", "bbb");
+        Assert.Equal(6, templater.Count);
+        templater.Add("assistant", "333");
+        Assert.Equal(7, templater.Count);
+        templater.Add("user", "ccc");
+        Assert.Equal(8, templater.Count);
+
+        // Call once with empty array to discover length
+        var length = templater.Apply(Array.Empty<byte>());
+        var dest = new byte[length];
+
+        Assert.Equal(8, templater.Count);
+
+        // Call again to get contents
+        length = templater.Apply(dest);
+
+        Assert.Equal(8, templater.Count);
+
+        var templateResult = Encoding.UTF8.GetString(dest.AsSpan(0, length));
+        const string expected = "<|im_start|>assistant\nhello<|im_end|>\n" +
+                                "<|im_start|>user\nworld<|im_end|>\n" +
+                                "<|im_start|>assistant\n" +
+                                "111<|im_end|>" +
+                                "\n<|im_start|>user\n" +
+                                "aaa<|im_end|>\n" +
+                                "<|im_start|>assistant\n" +
+                                "222<|im_end|>\n" +
+                                "<|im_start|>user\n" +
+                                "bbb<|im_end|>\n" +
+                                "<|im_start|>assistant\n" +
+                                "333<|im_end|>\n" +
+                                "<|im_start|>user\n" +
+                                "ccc<|im_end|>\n" +
+                                "<|im_start|>assistant\n";
+
+        Assert.Equal(expected, templateResult);
+    }
+
+    [Fact]
+    public void GetOutOfRangeThrows()
+    {
+        var templater = new LLamaTemplate(_model);
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => templater[0]);
+
+        templater.Add("assistant", "1");
+        templater.Add("user", "2");
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => templater[-1]);
+        Assert.Throws<ArgumentOutOfRangeException>(() => templater[2]);
+    }
+
+    [Fact]
+    public void RemoveMid()
+    {
+        var templater = new LLamaTemplate(_model);
+
+        templater.Add("assistant", "1");
+        templater.Add("user", "2");
+        templater.Add("assistant", "3");
+        templater.Add("user", "4a");
+        templater.Add("user", "4b");
+        templater.Add("assistant", "5");
+
+        Assert.Equal(("user", "4a"), templater[3]);
+        Assert.Equal(("assistant", "5"), templater[5]);
+
+        Assert.Equal(6, templater.Count);
+        templater.RemoveAt(3);
+        Assert.Equal(5, templater.Count);
+
+        Assert.Equal(("user", "4b"), templater[3]);
+        Assert.Equal(("assistant", "5"), templater[4]);
+    }
+
+    [Fact]
+    public void RemoveLast()
+    {
+        var templater = new LLamaTemplate(_model);
+
+        templater.Add("assistant", "1");
+        templater.Add("user", "2");
+        templater.Add("assistant", "3");
+        templater.Add("user", "4a");
+        templater.Add("user", "4b");
+        templater.Add("assistant", "5");
+
+        Assert.Equal(6, templater.Count);
+        templater.RemoveAt(5);
+        Assert.Equal(5, templater.Count);
+
+        Assert.Equal(("user", "4b"), templater[4]);
+    }
+
+    [Fact]
+    public void RemoveOutOfRange()
+    {
+        var templater = new LLamaTemplate(_model);
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => templater.RemoveAt(0));
+
+        templater.Add("assistant", "1");
+        templater.Add("user", "2");
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => templater.RemoveAt(-1));
+        Assert.Throws<ArgumentOutOfRangeException>(() => templater.RemoveAt(2));
+    }
+}