common : fix mirostat state when using multiple sequences (#3543)

* Fix mirostat state when using multiple sequences

* Fix mirostat by completely refactoring sampling!

* Try to fix zig build.

* Export function to fetch/create default sampler states

Code formatting cleanups and add some comments

Silence a warning about id not being used when logging is disabled

* Apply some renaming suggestions.

Fix comments that were out of sync with the pull.

* Use more consistant naming convention for sampling contexts

common/sampling.h

@@ -0,0 +1,108 @@
+#pragma once
+
+#include "llama.h"
+
+#include <string>
+#include <vector>
+#include <unordered_map>
+
+// sampling parameters
+typedef struct llama_sampling_params {
+    int32_t top_k             = 40;    // <= 0 to use vocab size
+    float   top_p             = 0.95f; // 1.0 = disabled
+    float   tfs_z             = 1.00f; // 1.0 = disabled
+    float   typical_p         = 1.00f; // 1.0 = disabled
+    float   temp              = 0.80f; // 1.0 = disabled
+    float   repeat_penalty    = 1.10f; // 1.0 = disabled
+    int32_t repeat_last_n     = 64;    // last n tokens to penalize (0 = disable penalty, -1 = context size)
+    float   frequency_penalty = 0.00f; // 0.0 = disabled
+    float   presence_penalty  = 0.00f; // 0.0 = disabled
+    int32_t mirostat          = 0;     // 0 = disabled, 1 = mirostat, 2 = mirostat 2.0
+    float   mirostat_tau      = 5.00f; // target entropy
+    float   mirostat_eta      = 0.10f; // learning rate
+
+    bool    penalize_nl       = true;  // consider newlines as a repeatable token
+
+    int32_t n_probs           = 0;     // if greater than 0, output the probabilities of top n_probs tokens.
+
+    // Classifier-Free Guidance
+    // https://arxiv.org/abs/2306.17806
+    std::string cfg_negative_prompt;   // string to help guidance
+    float       cfg_scale     = 1.f;   // How strong is guidance
+
+    std::unordered_map<llama_token, float> logit_bias; // logit bias for specific tokens
+
+} llama_sampling_params;
+
+// per-sequence sampler context
+typedef struct llama_sampler_sequence_context {
+    float mirostat_mu; // mirostat sampler state
+    llama_grammar * grammar;
+} llama_sampler_sequence_context;
+
+// general sampler context
+typedef struct llama_sampling_context {
+    ~llama_sampling_context();
+
+    // parameters that will be used for sampling and when creating
+    // new llama_sampler_sequence_context instances
+    llama_sampling_params params;
+
+    // map of sequence ids to sampler contexts
+    std::unordered_map<llama_seq_id, llama_sampler_sequence_context> sequence_contexts;
+
+    // when non-NULL, new instances of llama_sampler_sequence_context
+    // will get a copy of the grammar here
+    // note: only the pointer is stored here, it is not a copy of
+    //       the grammar and shouldn't be freed
+    llama_grammar * grammar;
+} llama_sampling_context;
+
+#include "common.h"
+
+// Create a new sampling context instance.
+llama_sampling_context llama_sampling_context_init(
+        const struct gpt_params & params,
+                  llama_grammar * grammar = NULL);
+
+// Fetches the sampler context for the specified sequence id (defaults to 0).
+// If the context for that sequence id doesn't already exist, it will be created with
+// default values based on the parameters in the ctx_sampling argument.
+llama_sampler_sequence_context & llama_sampling_get_sequence_context(
+              llama_sampling_context & ctx_sampling,
+        const llama_seq_id             seq = 0);
+
+// Reset the sampler context for the supplied sequence id (defaults to 0).
+// This is necessary to reuse a sequence id or free memory used by sequences
+// that are no longer required.
+bool llama_sampling_context_reset(
+              llama_sampling_context & ctx_sampling,
+        const llama_seq_id             seq = 0);
+
+// this is a common sampling function used across the examples for convenience
+// it can serve as a starting point for implementing your own sampling function
+// Note: When using multiple sequences, it is the caller's responsibility to call
+//       llama_sampling_context_reset when a sequence ends
+//
+// required:
+//  - ctx:          context to use for sampling
+//  - ctx_sampling: sampling-specific context
+//
+// optional:
+//  - ctx_guidance:  context to use for classifier-free guidance, ignore if NULL
+//  - last_tokens:   needed for repetition penalty, ignore if empty
+//  - idx:           sample from llama_get_logits_ith(ctx, idx)
+//  - seq:           sequence id to associate sampler state with
+//
+// returns:
+//  - token:      sampled token
+//  - candidates: vector of candidate tokens
+//
+llama_token llama_sampling_sample(
+                  struct llama_context * ctx,
+                  struct llama_context * ctx_guidance,
+                  struct llama_sampling_context & ctx_sampling,
+        const std::vector<llama_token> & last_tokens,
+         std::vector<llama_token_data> & candidates,
+        const                      int   idx = 0,
+                          llama_seq_id   seq = 0);