Automatically set chat format from gguf (#1110)

* Use jinja formatter to load chat format from gguf

* Fix off-by-one error in metadata loader

* Implement chat format auto-detection

Author: abetlen

llama_cpp/_internals.py

@@ -216,13 +216,13 @@ def metadata(self) -> Dict[str, str]:
         for i in range(llama_cpp.llama_model_meta_count(self.model)):
             nbytes = llama_cpp.llama_model_meta_key_by_index(self.model, i, buffer, buffer_size)
             if nbytes > buffer_size:
-                buffer_size = nbytes
+                buffer_size = nbytes + 1
                 buffer = ctypes.create_string_buffer(buffer_size)
                 nbytes = llama_cpp.llama_model_meta_key_by_index(self.model, i, buffer, buffer_size)
             key = buffer.value.decode("utf-8")
             nbytes = llama_cpp.llama_model_meta_val_str_by_index(self.model, i, buffer, buffer_size)
             if nbytes > buffer_size:
-                buffer_size = nbytes
+                buffer_size = nbytes + 1
                 buffer = ctypes.create_string_buffer(buffer_size)
                 nbytes = llama_cpp.llama_model_meta_val_str_by_index(self.model, i, buffer, buffer_size)
             value = buffer.value.decode("utf-8")

llama_cpp/llama.py

@@ -87,7 +87,7 @@ def __init__(
         # Backend Params
         numa: bool = False,
         # Chat Format Params
-        chat_format: str = "llama-2",
+        chat_format: Optional[str] = None,
         chat_handler: Optional[llama_chat_format.LlamaChatCompletionHandler] = None,
         # Misc
         verbose: bool = True,
@@ -343,6 +343,41 @@ def __init__(
         if self.verbose:
             print(f"Model metadata: {self.metadata}", file=sys.stderr)
 
+        if self.chat_format is None and self.chat_handler is None and "tokenizer.chat_template" in self.metadata:
+            chat_format = llama_chat_format.guess_chat_format_from_gguf_metadata(self.metadata)
+
+            if chat_format is not None:
+                self.chat_format = chat_format
+                if self.verbose:
+                    print(f"Guessed chat format: {chat_format}", file=sys.stderr)
+            else:
+                template = self.metadata["tokenizer.chat_template"]
+                try:
+                    eos_token_id = int(self.metadata["tokenizer.ggml.eos_token_id"])
+                except:
+                    eos_token_id = self.token_eos()
+                try:
+                    bos_token_id = int(self.metadata["tokenizer.ggml.bos_token_id"])
+                except:
+                    bos_token_id = self.token_bos()
+
+                eos_token = self.detokenize([eos_token_id]).decode("utf-8")
+                bos_token = self.detokenize([bos_token_id]).decode("utf-8")
+
+                if self.verbose:
+                    print(f"Using chat template: {template}", file=sys.stderr)
+                    print(f"Using chat eos_token: {eos_token}", file=sys.stderr)
+                    print(f"Using chat bos_token: {bos_token}", file=sys.stderr)
+
+                self.chat_handler = llama_chat_format.Jinja2ChatFormatter(
+                    template=template,
+                    eos_token=eos_token,
+                    bos_token=bos_token
+                ).to_chat_handler()
+
+        if self.chat_format is None and self.chat_handler is None:
+            self.chat_format = "llama-2"
+
     @property
     def ctx(self) -> llama_cpp.llama_context_p:
         assert self._ctx.ctx is not None

llama_cpp/llama_chat_format.py

@@ -14,6 +14,20 @@
 
 from ._utils import suppress_stdout_stderr, Singleton
 
+### Common Chat Templates and Special Tokens ###
+
+# Source: https://huggingface.co/teknium/OpenHermes-2.5-Mistral-7B/blob/main/tokenizer_config.json
+CHATML_CHAT_TEMPLATE = "{% for message in messages %}{{'<|im_start|>' + message['role'] + '\n' + message['content'] + '<|im_end|>' + '\n'}}{% endfor %}{% if add_generation_prompt %}{{ '<|im_start|>assistant\n' }}{% endif %}"
+CHATML_BOS_TOKEN = "<s>"
+CHATML_EOS_TOKEN = "<|im_end|>"
+
+# Source: https://huggingface.co/mistralai/Mistral-7B-Instruct-v0.1/blob/main/tokenizer_config.json
+MISTRAL_INSTRUCT_CHAT_TEMPLATE = "{{ bos_token }}{% for message in messages %}{% if (message['role'] == 'user') != (loop.index0 % 2 == 0) %}{{ raise_exception('Conversation roles must alternate user/assistant/user/assistant/...') }}{% endif %}{% if message['role'] == 'user' %}{{ '[INST] ' + message['content'] + ' [/INST]' }}{% elif message['role'] == 'assistant' %}{{ message['content'] + eos_token + ' ' }}{% else %}{{ raise_exception('Only user and assistant roles are supported!') }}{% endif %}{% endfor %}"
+MISTRAL_INSTRUCT_BOS_TOKEN = "<s>"
+MISTRAL_INSTRUCT_EOS_TOKEN = "</s>"
+
+
+### Chat Completion Handler ###
 
 class LlamaChatCompletionHandler(Protocol):
     """Base Protocol for a llama chat completion handler.
@@ -118,7 +132,6 @@ def decorator(f: LlamaChatCompletionHandler):
 
 ### Chat Formatter ###
 
-
 @dataclasses.dataclass
 class ChatFormatterResponse:
     """Dataclass that stores completion parameters for a given chat format and
@@ -440,7 +453,20 @@ def hf_tokenizer_config_to_chat_completion_handler(
     return chat_formatter_to_chat_completion_handler(chat_formatter)
 
 
+def guess_chat_format_from_gguf_metadata(metadata: Dict[str, str]) -> Optional[str]:
+    if "tokenizer.chat_template" not in metadata:
+        return None
+
+    if metadata["tokenizer.chat_template"] == CHATML_CHAT_TEMPLATE:
+        return "chatml"
+
+    if metadata["tokenizer.chat_template"] == MISTRAL_INSTRUCT_CHAT_TEMPLATE: 
+        return "mistral-instruct"
+
+    return None
+
 ### Utility functions for formatting chat prompts ###
+# TODO: Replace these with jinja2 templates
 
 
 def _get_system_message(
@@ -929,7 +955,6 @@ def format_openchat(
     _prompt = _format_chatml(system_message, _messages, _sep)
     return ChatFormatterResponse(prompt=_prompt, stop=_sep)
 
-
 # Chat format for Saiga models, see more details and available models:
 # https://huggingface.co/collections/IlyaGusev/saiga2-saigamistral-6505d4ccc3d1e53166b636cd
 @register_chat_format("saiga")
@@ -951,6 +976,7 @@ def format_saiga(
     _prompt += "<s>bot"
     return ChatFormatterResponse(prompt=_prompt.strip())
 
+# Tricky chat formats that require custom chat handlers
 
 @register_chat_completion_handler("functionary")
 def functionary_chat_handler(

llama_cpp/server/settings.py

@@ -113,8 +113,8 @@ class ModelSettings(BaseSettings):
         description="Enable NUMA support.",
     )
     # Chat Format Params
-    chat_format: str = Field(
-        default="llama-2",
+    chat_format: Optional[str] = Field(
+        default=None,
         description="Chat format to use.",
     )
     clip_model_path: Optional[str] = Field(