Add self‑speculative decoding (no draft model required)

CODEOWNERS

@@ -18,6 +18,7 @@
 /common/jinja/                          @ngxson @CISC @aldehir
 /common/llguidance.*                    @ggerganov
 /common/log.*                           @ggerganov
+/common/ngram-map.*                     @srogmann
 /common/peg-parser.*                    @aldehir
 /common/sampling.*                      @ggerganov
 /common/speculative.*                   @ggerganov

common/CMakeLists.txt

@@ -73,6 +73,8 @@ add_library(${TARGET} STATIC
     log.h
     ngram-cache.cpp
     ngram-cache.h
+    ngram-map.cpp
+    ngram-map.h
     peg-parser.cpp
     peg-parser.h
     preset.cpp

common/arg.cpp

@@ -6,6 +6,7 @@
 #include "json-schema-to-grammar.h"
 #include "log.h"
 #include "sampling.h"
+#include "speculative.h"
 #include "preset.h"
 
 // fix problem with std::min and std::max
@@ -579,14 +580,14 @@ static bool common_params_parse_ex(int argc, char ** argv, common_params_context
             params.mmproj = res.mmproj;
         }
         // only download mmproj if the current example is using it
-        for (auto & ex : mmproj_examples) {
+        for (const auto & ex : mmproj_examples) {
             if (ctx_arg.ex == ex) {
                 common_params_handle_model(params.mmproj,    params.hf_token, params.offline);
                 break;
             }
         }
-        common_params_handle_model(params.speculative.model, params.hf_token, params.offline);
-        common_params_handle_model(params.vocoder.model,     params.hf_token, params.offline);
+        common_params_handle_model(params.speculative.mparams_dft, params.hf_token, params.offline);
+        common_params_handle_model(params.vocoder.model,           params.hf_token, params.offline);
     }
 
     // model is required (except for server)
@@ -1216,16 +1217,16 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
         {"-lcs", "--lookup-cache-static"}, "FNAME",
         "path to static lookup cache to use for lookup decoding (not updated by generation)",
         [](common_params & params, const std::string & value) {
-            params.lookup_cache_static = value;
+            params.speculative.lookup_cache_static = value;
         }
-    ).set_examples({LLAMA_EXAMPLE_LOOKUP}));
+    ).set_examples({LLAMA_EXAMPLE_LOOKUP, LLAMA_EXAMPLE_SERVER}));
     add_opt(common_arg(
         {"-lcd", "--lookup-cache-dynamic"}, "FNAME",
         "path to dynamic lookup cache to use for lookup decoding (updated by generation)",
         [](common_params & params, const std::string & value) {
-            params.lookup_cache_dynamic = value;
+            params.speculative.lookup_cache_dynamic = value;
         }
-    ).set_examples({LLAMA_EXAMPLE_LOOKUP}));
+    ).set_examples({LLAMA_EXAMPLE_LOOKUP, LLAMA_EXAMPLE_SERVER}));
     add_opt(common_arg(
         {"-c", "--ctx-size"}, "N",
         string_format("size of the prompt context (default: %d, 0 = loaded from model)", params.n_ctx),
@@ -2565,7 +2566,7 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
         {"-hfd", "-hfrd", "--hf-repo-draft"}, "<user>/<model>[:quant]",
         "Same as --hf-repo, but for the draft model (default: unused)",
         [](common_params & params, const std::string & value) {
-            params.speculative.model.hf_repo = value;
+            params.speculative.mparams_dft.hf_repo = value;
         }
     ).set_env("LLAMA_ARG_HFD_REPO"));
     add_opt(common_arg(
@@ -3386,7 +3387,7 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
         {"-md", "--model-draft"}, "FNAME",
         "draft model for speculative decoding (default: unused)",
         [](common_params & params, const std::string & value) {
-            params.speculative.model.path = value;
+            params.speculative.mparams_dft.path = value;
         }
     ).set_examples({LLAMA_EXAMPLE_SPECULATIVE, LLAMA_EXAMPLE_SERVER, LLAMA_EXAMPLE_CLI}).set_env("LLAMA_ARG_MODEL_DRAFT"));
     add_opt(common_arg(
@@ -3396,6 +3397,66 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
             params.speculative.replacements.push_back({ tgt, dft });
         }
     ).set_examples({LLAMA_EXAMPLE_SPECULATIVE, LLAMA_EXAMPLE_SERVER, LLAMA_EXAMPLE_CLI}));
+    add_opt(common_arg(
+        {"--spec-type"}, "[none|ngram-cache|ngram-simple|ngram-map-k|ngram-map-k4v]",
+        string_format("type of speculative decoding to use when no draft model is provided (default: %s)\n",
+            common_speculative_type_to_str(params.speculative.type).c_str()),
+        [](common_params & params, const std::string & value) {
+            if (value == "none") {
+                params.speculative.type = COMMON_SPECULATIVE_TYPE_NONE;
+            } else if (value == "ngram-cache") {
+                params.speculative.type = COMMON_SPECULATIVE_TYPE_NGRAM_CACHE;
+            } else if (value == "ngram-simple") {
+                params.speculative.type = COMMON_SPECULATIVE_TYPE_NGRAM_SIMPLE;
+            } else if (value == "ngram-map-k") {
+                params.speculative.type = COMMON_SPECULATIVE_TYPE_NGRAM_MAP_K;
+            } else if (value == "ngram-map-k4v") {
+                params.speculative.type = COMMON_SPECULATIVE_TYPE_NGRAM_MAP_K4V;
+            } else {
+                throw std::invalid_argument("unknown speculative decoding type without draft model");
+            }
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}));
+    add_opt(common_arg(
+        {"--spec-ngram-size-n"}, "N",
+        string_format("ngram size N for ngram-simple/ngram-map speculative decoding, length of lookup n-gram (default: %d)", params.speculative.ngram_size_n),
+        [](common_params & params, int value) {
+            if (value < 1 || value > 1024) {
+                throw std::invalid_argument("ngram size N must be between 1 and 1024 inclusive");
+            }
+            params.speculative.ngram_size_n = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}));
+    add_opt(common_arg(
+        {"--spec-ngram-size-m"}, "N",
+        string_format("ngram size M for ngram-simple/ngram-map speculative decoding, length of draft m-gram (default: %d)", params.speculative.ngram_size_m),
+        [](common_params & params, int value) {
+            if (value < 1 || value > 1024) {
+                throw std::invalid_argument("ngram size M must be between 1 and 1024 inclusive");
+            }
+            params.speculative.ngram_size_m = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}));
+    add_opt(common_arg(
+        {"--spec-ngram-check-rate"}, "N",
+        string_format("ngram check rate for ngram-simple/ngram-map speculative decoding (default: %d)", params.speculative.ngram_check_rate),
+        [](common_params & params, int value) {
+            if (value < 1) {
+                throw std::invalid_argument("ngram check rate must be at least 1");
+            }
+            params.speculative.ngram_check_rate = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}));
+    add_opt(common_arg(
+        {"--spec-ngram-min-hits"}, "N",
+        string_format("minimum hits for ngram-map speculative decoding (default: %d)", params.speculative.ngram_min_hits),
+        [](common_params & params, int value) {
+            if (value < 1) {
+                throw std::invalid_argument("ngram min hits must be at least 1");
+            }
+            params.speculative.ngram_min_hits = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}));
     add_opt(common_arg(
         {"-ctkd", "--cache-type-k-draft"}, "TYPE",
         string_format(
@@ -3622,8 +3683,8 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
         [](common_params & params) {
             params.model.hf_repo = "ggml-org/Qwen2.5-Coder-7B-Q8_0-GGUF";
             params.model.hf_file = "qwen2.5-coder-7b-q8_0.gguf";
-            params.speculative.model.hf_repo = "ggml-org/Qwen2.5-Coder-0.5B-Q8_0-GGUF";
-            params.speculative.model.hf_file = "qwen2.5-coder-0.5b-q8_0.gguf";
+            params.speculative.mparams_dft.hf_repo = "ggml-org/Qwen2.5-Coder-0.5B-Q8_0-GGUF";
+            params.speculative.mparams_dft.hf_file = "qwen2.5-coder-0.5b-q8_0.gguf";
             params.port = 8012;
             params.n_ubatch = 1024;
             params.n_batch = 1024;
@@ -3638,8 +3699,8 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
         [](common_params & params) {
             params.model.hf_repo = "ggml-org/Qwen2.5-Coder-14B-Q8_0-GGUF";
             params.model.hf_file = "qwen2.5-coder-14b-q8_0.gguf";
-            params.speculative.model.hf_repo = "ggml-org/Qwen2.5-Coder-0.5B-Q8_0-GGUF";
-            params.speculative.model.hf_file = "qwen2.5-coder-0.5b-q8_0.gguf";
+            params.speculative.mparams_dft.hf_repo = "ggml-org/Qwen2.5-Coder-0.5B-Q8_0-GGUF";
+            params.speculative.mparams_dft.hf_file = "qwen2.5-coder-0.5b-q8_0.gguf";
             params.port = 8012;
             params.n_ubatch = 1024;
             params.n_batch = 1024;

common/common.cpp

@@ -1097,7 +1097,10 @@ common_init_result::common_init_result(common_params & params) :
     if (params.fit_params) {
         LOG_INF("%s: fitting params to device memory, for bugs during this step try to reproduce them with -fit off, or provide --verbose logs if the bug only occurs with -fit on\n", __func__);
         llama_params_fit(params.model.path.c_str(), &mparams, &cparams,
-            params.tensor_split, params.tensor_buft_overrides.data(), params.fit_params_target.data(), params.fit_params_min_ctx,
+            params.tensor_split,
+            params.tensor_buft_overrides.data(),
+            params.fit_params_target.data(),
+            params.fit_params_min_ctx,
             params.verbosity >= 4 ? GGML_LOG_LEVEL_DEBUG : GGML_LOG_LEVEL_ERROR);
     }
 
@@ -1208,10 +1211,6 @@ std::vector<llama_adapter_lora_ptr> & common_init_result::lora() {
     return pimpl->lora;
 }
 
-void common_init_result::free_context() {
-    pimpl->context.reset();
-}
-
 common_init_result_ptr common_init_from_params(common_params & params) {
     common_init_result_ptr res(new common_init_result(params));
 

common/common.h

@@ -164,6 +164,16 @@ enum common_params_sampling_config : uint64_t {
     COMMON_PARAMS_SAMPLING_CONFIG_MIROSTAT_ETA    = 1 << 11,
 };
 
+enum common_speculative_type {
+    COMMON_SPECULATIVE_TYPE_NONE,          // no speculative decoding
+    COMMON_SPECULATIVE_TYPE_DRAFT,         // draft model
+    COMMON_SPECULATIVE_TYPE_EAGLE3,        // eagle draft model
+    COMMON_SPECULATIVE_TYPE_NGRAM_SIMPLE,  // simple self-speculative decoding
+    COMMON_SPECULATIVE_TYPE_NGRAM_MAP_K,   // self-speculative decoding with n-gram keys only
+    COMMON_SPECULATIVE_TYPE_NGRAM_MAP_K4V, // self-speculative decoding with n-gram keys and 4 m-gram values
+    COMMON_SPECULATIVE_TYPE_NGRAM_CACHE,   // self-speculative decoding with 3-level n-gram cache
+    COMMON_SPECULATIVE_TYPE_COUNT          // number of types, unknown type
+};
 
 // sampling parameters
 struct common_params_sampling {
@@ -243,24 +253,50 @@ struct common_params_model {
 };
 
 struct common_params_speculative {
-    std::vector<ggml_backend_dev_t> devices; // devices to use for offloading
+    common_speculative_type type = COMMON_SPECULATIVE_TYPE_NONE; // type of speculative decoding
 
-    int32_t n_ctx        =     0; // draft context size
-    int32_t n_max        =    16; // maximum number of tokens to draft during speculative decoding
-    int32_t n_min        =     0; // minimum number of draft tokens to use for speculative decoding
-    int32_t n_gpu_layers =    -1; // number of layers to store in VRAM for the draft model (-1 - use default)
-    float   p_split      =  0.1f; // speculative decoding split probability
-    float   p_min        = 0.75f; // minimum speculative decoding probability (greedy)
-    std::vector<std::pair<std::string, std::string>> replacements; // main to speculative model replacements
-    std::vector<llama_model_tensor_buft_override> tensor_buft_overrides;
+    // general-purpose speculative decoding parameters
+
+    int32_t n_max   = 16; // maximum number of tokens to draft during speculative decoding
+    int32_t n_min   = 0; // minimum number of draft tokens to use for speculative decoding
+    float   p_split = 0.1f; // speculative decoding split probability
+    float   p_min   = 0.75f; // minimum speculative decoding probability (greedy)
+
+    // ngram-based speculative decoding
+
+    uint16_t ngram_size_n     = 12; // ngram size for lookup
+    uint16_t ngram_size_m     = 48; // mgram size for speculative tokens
+    uint16_t ngram_check_rate =  1; // check rate for ngram lookup
+    uint16_t ngram_min_hits   =  1; // minimum hits at ngram/mgram lookup for mgram to be proposed
+
+    std::string lookup_cache_static;  // path of static ngram cache file for lookup decoding           // NOLINT
+    std::string lookup_cache_dynamic; // path of dynamic ngram cache file for lookup decoding          // NOLINT
+
+    // draft-model speculative decoding
+
+    struct common_params_model mparams_dft;
+
+    llama_model * model_dft = nullptr; // a llama_model that can be shared by multiple speculative contexts
+
+    llama_context_params cparams_dft; // these are the parameters for the draft llama_context
+
+    int32_t n_ctx        = 0;  // draft context size
+    int32_t n_gpu_layers = -1; // number of layers to store in VRAM for the draft model (-1 - use default)
 
     ggml_type cache_type_k = GGML_TYPE_F16; // KV cache data type for the K
     ggml_type cache_type_v = GGML_TYPE_F16; // KV cache data type for the V
 
     struct cpu_params cpuparams;
     struct cpu_params cpuparams_batch;
 
-    struct common_params_model model;
+    std::vector<ggml_backend_dev_t> devices; // devices to use for offloading
+
+    std::vector<std::pair<std::string, std::string>> replacements; // main to speculative model replacements
+    std::vector<llama_model_tensor_buft_override> tensor_buft_overrides;
+
+    bool has_dft() const {
+        return !mparams_dft.path.empty() || !mparams_dft.hf_repo.empty();
+    }
 };
 
 struct common_params_vocoder {
@@ -378,8 +414,6 @@ struct common_params {
     std::string path_prompt_cache    = ""; // path to file for saving/loading prompt eval state             // NOLINT
     std::string input_prefix         = ""; // string to prefix user inputs with                             // NOLINT
     std::string input_suffix         = ""; // string to suffix user inputs with                             // NOLINT
-    std::string lookup_cache_static  = ""; // path of static ngram cache file for lookup decoding           // NOLINT
-    std::string lookup_cache_dynamic = ""; // path of dynamic ngram cache file for lookup decoding          // NOLINT
     std::string logits_file          = ""; // file for saving *all* logits                                  // NOLINT
 
     // llama-debug specific options
@@ -575,10 +609,6 @@ struct common_params {
     // return false from callback to abort model loading or true to continue
     llama_progress_callback load_progress_callback = NULL;
     void *                  load_progress_callback_user_data = NULL;
-
-    bool has_speculative() const {
-        return !speculative.model.path.empty() || !speculative.model.hf_repo.empty();
-    }
 };
 
 // call once at the start of a program if it uses libcommon
@@ -714,8 +744,6 @@ struct common_init_result {
 
     std::vector<llama_adapter_lora_ptr> & lora();
 
-    void free_context();
-
 private:
     struct impl;
     std::unique_ptr<impl> pimpl;

common/ngram-cache.cpp

@@ -192,12 +192,12 @@ void common_ngram_cache_draft(
             break;
         }
 
-        LOG(" - draft candidate: token=%d\n", drafted_token);
+        LOG_DBG(" - draft candidate: token=%d\n", drafted_token);
         draft.push_back(drafted_token);
     }
 }
 
-void common_ngram_cache_save(common_ngram_cache & ngram_cache, std::string & filename) {
+void common_ngram_cache_save(common_ngram_cache & ngram_cache, const std::string & filename) {
     std::ofstream file_out(filename, std::ios::binary);
     for (std::pair<common_ngram, common_ngram_cache_part> item : ngram_cache) {
         const common_ngram      ngram        = item.first;
@@ -217,10 +217,9 @@ void common_ngram_cache_save(common_ngram_cache & ngram_cache, std::string & fil
             file_out.write(reinterpret_cast<const char *>(&count), sizeof(int32_t));
         }
     }
-
 }
 
-common_ngram_cache common_ngram_cache_load(std::string & filename) {
+common_ngram_cache common_ngram_cache_load(const std::string & filename) {
     std::ifstream hashmap_file(filename, std::ios::binary);
     if (!hashmap_file) {
         throw std::ifstream::failure("Unable to open file " + filename);

common/ngram-cache.h

@@ -88,12 +88,12 @@ void common_ngram_cache_draft(
 // Save an ngram cache to a file.
 // ngram_cache: the ngram cache to save.
 // filename:    the path under which to save the ngram cache.
-void common_ngram_cache_save(common_ngram_cache & ngram_cache, std::string & filename);
+void common_ngram_cache_save(common_ngram_cache & ngram_cache, const std::string & filename);
 
 // Load an ngram cache saved with common_ngram_cache_save.
 // filename: the path from which to load the ngram cache.
 // returns:  an ngram cache containing the information saved to filename.
-common_ngram_cache common_ngram_cache_load(std::string & filename);
+common_ngram_cache common_ngram_cache_load(const std::string & filename);
 
 // Merge two ngram caches.
 // ngram_cache_target: the ngram cache to which to add the information from ngram_cache_add.