Implement new sampler API

This commit implements the new sampler API from `llama.cpp`
introduced in b3680 and removes the custom sampling logic.

The new sampling API is exposes through a builder pattern.

Made tests pass.

examples/simple/src/main.rs

@@ -17,7 +17,9 @@ use llama_cpp_2::model::params::kv_overrides::ParamOverrideValue;
 use llama_cpp_2::model::params::LlamaModelParams;
 use llama_cpp_2::model::LlamaModel;
 use llama_cpp_2::model::{AddBos, Special};
-use llama_cpp_2::token::data_array::LlamaTokenDataArray;
+use llama_cpp_2::sampling::params::LlamaSamplerChainParams;
+use llama_cpp_2::sampling::LlamaSampler;
+
 use std::ffi::CString;
 use std::io::Write;
 use std::num::NonZeroU32;
@@ -174,9 +176,9 @@ fn main() -> Result<()> {
         .with_context(|| "unable to load model")?;
 
     // initialize the context
-    let mut ctx_params = LlamaContextParams::default()
-        .with_n_ctx(ctx_size.or(Some(NonZeroU32::new(2048).unwrap())))
-        .with_seed(seed.unwrap_or(1234));
+    let mut ctx_params =
+        LlamaContextParams::default().with_n_ctx(ctx_size.or(Some(NonZeroU32::new(2048).unwrap())));
+
     if let Some(threads) = threads {
         ctx_params = ctx_params.with_n_threads(threads);
     }
@@ -244,31 +246,31 @@ either reduce n_len or increase n_ctx"
     // The `Decoder`
     let mut decoder = encoding_rs::UTF_8.new_decoder();
 
+    let sampler_params = LlamaSamplerChainParams::default();
+    let mut sampler = LlamaSampler::new(sampler_params)?.add_dist(seed.unwrap_or(1234));
+
     while n_cur <= n_len {
         // sample the next token
         {
-            let candidates = ctx.candidates();
-
-            let candidates_p = LlamaTokenDataArray::from_iter(candidates, false);
+            let token = sampler.sample(&ctx, batch.n_tokens() - 1);
 
-            // sample the most likely token
-            let new_token_id = ctx.sample_token_greedy(candidates_p);
+            sampler.accept(token);
 
             // is it an end of stream?
-            if model.is_eog_token(new_token_id) {
+            if model.is_eog_token(token) {
                 eprintln!();
                 break;
             }
 
-            let output_bytes = model.token_to_bytes(new_token_id, Special::Tokenize)?;
+            let output_bytes = model.token_to_bytes(token, Special::Tokenize)?;
             // use `Decoder.decode_to_string()` to avoid the intermediate buffer
             let mut output_string = String::with_capacity(32);
             let _decode_result = decoder.decode_to_string(&output_bytes, &mut output_string, false);
             print!("{output_string}");
             std::io::stdout().flush()?;
 
             batch.clear();
-            batch.add(new_token_id, n_cur, &[0], true)?;
+            batch.add(token, n_cur, &[0], true)?;
         }
 
         n_cur += 1;

examples/usage.rs

@@ -14,6 +14,8 @@ use llama_cpp_2::llama_batch::LlamaBatch;
 use llama_cpp_2::model::params::LlamaModelParams;
 use llama_cpp_2::model::LlamaModel;
 use llama_cpp_2::model::{AddBos, Special};
+use llama_cpp_2::sampling::params::LlamaSamplerChainParams;
+use llama_cpp_2::sampling::LlamaSampler;
 use llama_cpp_2::token::data_array::LlamaTokenDataArray;
 use std::io::Write;
 
@@ -54,33 +56,33 @@ fn main() {
     // The `Decoder`
     let mut decoder = encoding_rs::UTF_8.new_decoder();
 
+    let sampler_params = LlamaSamplerChainParams::default();
+    let mut sampler = LlamaSampler::new(sampler_params)
+        .expect("Failed to create sampler")
+        .add_greedy();
+
     while n_cur <= n_len {
         // sample the next token
         {
-            let candidates = ctx.candidates_ith(batch.n_tokens() - 1);
-
-            let candidates_p = LlamaTokenDataArray::from_iter(candidates, false);
+            let token = sampler.sample(&ctx, batch.n_tokens() - 1);
 
-            // sample the most likely token
-            let new_token_id = ctx.sample_token_greedy(candidates_p);
+            sampler.accept(token);
 
             // is it an end of stream?
-            if new_token_id == model.token_eos() {
+            if token == model.token_eos() {
                 eprintln!();
                 break;
             }
 
-            let output_bytes = model
-                .token_to_bytes(new_token_id, Special::Tokenize)
-                .unwrap();
+            let output_bytes = model.token_to_bytes(token, Special::Tokenize).unwrap();
             // use `Decoder.decode_to_string()` to avoid the intermediate buffer
             let mut output_string = String::with_capacity(32);
             let _decode_result = decoder.decode_to_string(&output_bytes, &mut output_string, false);
             print!("{output_string}");
             std::io::stdout().flush().unwrap();
 
             batch.clear();
-            batch.add(new_token_id, n_cur, &[0], true).unwrap();
+            batch.add(token, n_cur, &[0], true).unwrap();
         }
 
         n_cur += 1;

llama-cpp-2/src/context/params.rs

@@ -47,7 +47,7 @@ impl From<RopeScalingType> for i32 {
 pub enum LlamaPoolingType {
     /// The pooling type is unspecified
     Unspecified = -1,
-    /// No pooling    
+    /// No pooling
     None = 0,
     /// Mean pooling
     Mean = 1,
@@ -95,10 +95,8 @@ impl From<LlamaPoolingType> for i32 {
 /// use llama_cpp_2::context::params::LlamaContextParams;
 ///
 ///let ctx_params = LlamaContextParams::default()
-///    .with_n_ctx(NonZeroU32::new(2048))
-///    .with_seed(1234);
+///    .with_n_ctx(NonZeroU32::new(2048));
 ///
-/// assert_eq!(ctx_params.seed(), 1234);
 /// assert_eq!(ctx_params.n_ctx(), NonZeroU32::new(2048));
 /// ```
 #[derive(Debug, Clone)]