Two small improvements to the native sampling API:

- Modified `llama_sample_token_mirostat` and `llama_sample_token_mirostat_v2` to take `ref float` instead of as a `float*`. Less pointers is always good.
 - Modified `llama_sample_repetition_penalty` and `llama_sample_frequency_and_presence_penalties` to take pointers instead of arrays. This allows the use non non allocating types (e.g. Span) instead of arrays
 - Modified higher level API to accept `Memory<int>` instead of `int[]`, which can be used to reduce allocations at call sites

LLama/Native/NativeApi.Sampling.cs

@@ -26,7 +26,7 @@ namespace LLama.Native
         /// <param name="last_tokens_size"></param>
         /// <param name="penalty"></param>
         [DllImport(libraryName, CallingConvention = CallingConvention.Cdecl)]
-        public static extern void llama_sample_repetition_penalty(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, llama_token[] last_tokens, ulong last_tokens_size, float penalty);
+        public static extern void llama_sample_repetition_penalty(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, llama_token* last_tokens, ulong last_tokens_size, float penalty);
 
         /// <summary>
         /// Frequency and presence penalties described in OpenAI API https://platform.openai.com/docs/api-reference/parameter-details.
@@ -38,7 +38,7 @@ namespace LLama.Native
         /// <param name="alpha_frequency"></param>
         /// <param name="alpha_presence"></param>
         [DllImport(libraryName, CallingConvention = CallingConvention.Cdecl)]
-        public static extern void llama_sample_frequency_and_presence_penalties(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, llama_token[] last_tokens, ulong last_tokens_size, float alpha_frequency, float alpha_presence);
+        public static extern void llama_sample_frequency_and_presence_penalties(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, llama_token* last_tokens, ulong last_tokens_size, float alpha_frequency, float alpha_presence);
 
         /// <summary>
         /// Apply classifier-free guidance to the logits as described in academic paper "Stay on topic with Classifier-Free Guidance" https://arxiv.org/abs/2306.17806
@@ -118,7 +118,7 @@ namespace LLama.Native
         /// <param name="mu">Maximum cross-entropy. This value is initialized to be twice the target cross-entropy (`2 * tau`) and is updated in the algorithm based on the error between the target and observed surprisal.</param>
         /// <returns></returns>
         [DllImport(libraryName, CallingConvention = CallingConvention.Cdecl)]
-        public static extern llama_token llama_sample_token_mirostat(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, float tau, float eta, int m, float* mu);
+        public static extern llama_token llama_sample_token_mirostat(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, float tau, float eta, int m, ref float mu);
 
         /// <summary>
         /// Mirostat 2.0 algorithm described in the paper https://arxiv.org/abs/2007.14966. Uses tokens instead of words.
@@ -130,7 +130,7 @@ namespace LLama.Native
         /// <param name="mu">Maximum cross-entropy. This value is initialized to be twice the target cross-entropy (`2 * tau`) and is updated in the algorithm based on the error between the target and observed surprisal.</param>
         /// <returns></returns>
         [DllImport(libraryName, CallingConvention = CallingConvention.Cdecl)]
-        public static extern llama_token llama_sample_token_mirostat_v2(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, float tau, float eta, float* mu);
+        public static extern llama_token llama_sample_token_mirostat_v2(SafeLLamaContextHandle ctx, ref LLamaTokenDataArrayNative candidates, float tau, float eta, ref float mu);
 
         /// <summary>
         /// Selects the token with the highest probability.

LLama/Native/SamplingApi.cs

@@ -25,10 +25,12 @@ namespace LLama.Native
         /// <param name="last_tokens"></param>
         /// <param name="last_tokens_size"></param>
         /// <param name="penalty"></param>
-        public static void llama_sample_repetition_penalty(SafeLLamaContextHandle ctx, LLamaTokenDataArray candidates, llama_token[] last_tokens, ulong last_tokens_size, float penalty)
+        public static void llama_sample_repetition_penalty(SafeLLamaContextHandle ctx, LLamaTokenDataArray candidates, Memory<llama_token> last_tokens, ulong last_tokens_size, float penalty)
         {
             using var handle = LLamaTokenDataArrayNative.Create(candidates, out var st);
-            NativeApi.llama_sample_repetition_penalty(ctx, ref st, last_tokens, last_tokens_size, penalty);
+            using var last_tokens_handle = last_tokens.Pin();
+
+            NativeApi.llama_sample_repetition_penalty(ctx, ref st, (int*)last_tokens_handle.Pointer, last_tokens_size, penalty);
         }
 
         /// <summary>
@@ -40,10 +42,12 @@ namespace LLama.Native
         /// <param name="last_tokens_size"></param>
         /// <param name="alpha_frequency"></param>
         /// <param name="alpha_presence"></param>
-        public static void llama_sample_frequency_and_presence_penalties(SafeLLamaContextHandle ctx, LLamaTokenDataArray candidates, llama_token[] last_tokens, ulong last_tokens_size, float alpha_frequency, float alpha_presence)
+        public static void llama_sample_frequency_and_presence_penalties(SafeLLamaContextHandle ctx, LLamaTokenDataArray candidates, Memory<llama_token> last_tokens, ulong last_tokens_size, float alpha_frequency, float alpha_presence)
         {
             using var handle = LLamaTokenDataArrayNative.Create(candidates, out var st);
-            NativeApi.llama_sample_frequency_and_presence_penalties(ctx, ref st, last_tokens, last_tokens_size, alpha_frequency, alpha_presence);
+            using var last_tokens_handle = last_tokens.Pin();
+
+            NativeApi.llama_sample_frequency_and_presence_penalties(ctx, ref st, (int*)last_tokens_handle.Pointer, last_tokens_size, alpha_frequency, alpha_presence);
         }
 
         /// <summary>
@@ -128,10 +132,7 @@ namespace LLama.Native
         public static llama_token llama_sample_token_mirostat(SafeLLamaContextHandle ctx, LLamaTokenDataArray candidates, float tau, float eta, int m, ref float mu)
         {
             using var handle = LLamaTokenDataArrayNative.Create(candidates, out var st);
-            fixed(float* pmu = &mu)
-            {
-                return NativeApi.llama_sample_token_mirostat(ctx, ref st, tau, eta, m, pmu);
-            }
+            return NativeApi.llama_sample_token_mirostat(ctx, ref st, tau, eta, m, ref mu);
         }
 
         /// <summary>
@@ -146,10 +147,7 @@ namespace LLama.Native
         public static llama_token llama_sample_token_mirostat_v2(SafeLLamaContextHandle ctx, LLamaTokenDataArray candidates, float tau, float eta, ref float mu)
         {
             using var handle = LLamaTokenDataArrayNative.Create(candidates, out var st);
-            fixed (float* pmu = &mu)
-            {
-                return NativeApi.llama_sample_token_mirostat_v2(ctx, ref st, tau, eta, pmu);
-            }
+            return NativeApi.llama_sample_token_mirostat_v2(ctx, ref st, tau, eta, ref mu);
         }
 
         /// <summary>