common: support --models-dir loading MTP assistant models (#24431)

* common: support --models-dir loading MTP assistant models

* common: preset: check for MTP models with strict prefix

* common: preset: Take advantage of PR #27005

* handle other draft types

* drop eagle3

* clean up

---------

Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

common/preset.cpp

@@ -365,8 +365,25 @@ struct local_model {
     std::string name;
     std::string path;
     std::string path_mmproj;
+    std::string path_draft;
 };
 
+// TODO @ngxson: handle "eagle3-" when it's supported by common_speculative_types_from_gguf()
+static const char * draft_prefixes[] = { "mtp-", "dspark-", "dflash-" };
+
+static bool is_mmproj_file(const std::string & fname) {
+    return fname.find("mmproj") != std::string::npos;
+}
+
+static bool is_draft_file(const std::string & fname) {
+    for (const auto & prefix : draft_prefixes) {
+        if (fname.rfind(prefix, 0) == 0) {
+            return true;
+        }
+    }
+    return false;
+}
+
 common_presets common_preset_context::load_from_models_dir(const std::string & models_dir) const {
     if (!std::filesystem::exists(models_dir) || !std::filesystem::is_directory(models_dir)) {
         throw std::runtime_error(string_format("error: '%s' does not exist or is not a directory\n", models_dir.c_str()));
@@ -378,10 +395,15 @@ common_presets common_preset_context::load_from_models_dir(const std::string & m
         common_file_info model_file;
         common_file_info first_shard_file;
         common_file_info mmproj_file;
+        common_file_info draft_file;
         for (const auto & file : files) {
             if (string_ends_with(file.name, ".gguf")) {
-                if (file.name.find("mmproj") != std::string::npos) {
+                if (is_mmproj_file(file.name)) {
                     mmproj_file = file;
+                } else if (is_draft_file(file.name)) {
+                    if (draft_file.path.empty()) {
+                        draft_file = file; // first sidecar found wins
+                    }
                 } else if (file.name.find("-00001-of-") != std::string::npos) {
                     first_shard_file = file;
                 } else {
@@ -393,7 +415,8 @@ common_presets common_preset_context::load_from_models_dir(const std::string & m
         local_model model{
             /* name        */ name,
             /* path        */ first_shard_file.path.empty() ? model_file.path : first_shard_file.path,
-            /* path_mmproj */ mmproj_file.path // can be empty
+            /* path_mmproj */ mmproj_file.path, // can be empty
+            /* path_draft  */ draft_file.path   // can be empty
         };
         if (!model.path.empty()) {
             models.push_back(model);
@@ -405,13 +428,17 @@ common_presets common_preset_context::load_from_models_dir(const std::string & m
         if (file.is_dir) {
             scan_subdir(file.path, file.name);
         } else if (string_ends_with(file.name, ".gguf")) {
+            if (is_mmproj_file(file.name) || is_draft_file(file.name)) {
+                continue; // companion file, cannot be loaded as a model on its own
+            }
             // single file model
             std::string name = file.name;
             string_replace_all(name, ".gguf", "");
             local_model model{
                 /* name        */ name,
                 /* path        */ file.path,
-                /* path_mmproj */ ""
+                /* path_mmproj */ "",
+                /* path_draft  */ ""
             };
             models.push_back(model);
         }
@@ -426,6 +453,9 @@ common_presets common_preset_context::load_from_models_dir(const std::string & m
         if (!model.path_mmproj.empty()) {
             preset.set_option(*this, "LLAMA_ARG_MMPROJ", model.path_mmproj);
         }
+        if (!model.path_draft.empty()) {
+            preset.set_option(*this, "LLAMA_ARG_SPEC_DRAFT_MODEL", model.path_draft);
+        }
         out[preset.name] = preset;
     }