spec : add ngram-mod (#19164)

* spec : add ngram-mod

* cont : simplify + keep track of occupancy

* cont : cleanup

* cont : move initialization to common/speculative

* cont : cleanup

* cont : cleanup

* cont : fix

common/common.h

@@ -171,6 +171,7 @@ enum common_speculative_type {
     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_MOD,
     COMMON_SPECULATIVE_TYPE_NGRAM_CACHE,   // self-speculative decoding with 3-level n-gram cache
     COMMON_SPECULATIVE_TYPE_COUNT          // number of types, unknown type
 };
@@ -252,6 +253,8 @@ struct common_params_model {
     std::string name        = ""; // in format <user>/<model>[:<tag>] (tag is optional)     // NOLINT
 };
 
+struct common_ngram_mod;
+
 struct common_params_speculative {
     common_speculative_type type = COMMON_SPECULATIVE_TYPE_NONE; // type of speculative decoding
 
@@ -269,6 +272,8 @@ struct common_params_speculative {
     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::shared_ptr<common_ngram_mod> ngram_mod;
+
     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