Add seperate lora_base path for applying LoRA to quantized models using original unquantized model weights.

Author: abetlen

llama_cpp/llama.py

@@ -39,6 +39,7 @@ def __init__(
         n_threads: Optional[int] = None,
         n_batch: int = 8,
         last_n_tokens_size: int = 64,
+        lora_base: Optional[str] = None,
         lora_path: Optional[str] = None,
         verbose: bool = True,
     ):
@@ -58,6 +59,7 @@ def __init__(
             n_threads: Number of threads to use. If None, the number of threads is automatically determined.
             n_batch: Maximum number of prompt tokens to batch together when calling llama_eval.
             last_n_tokens_size: Maximum number of tokens to keep in the last_n_tokens deque.
+            lora_base: Optional path to base model, useful if using a quantized base model and you want to apply LoRA to an f16 model.
             lora_path: Path to a LoRA file to apply to the model.
             verbose: Print verbose output to stderr.
 
@@ -110,16 +112,21 @@ def __init__(
             self.model_path.encode("utf-8"), self.params
         )
 
+        self.lora_base = None
         self.lora_path = None
         if lora_path:
+            self.lora_base = lora_base
+            # Use lora_base if set otherwise revert to using model_path.
+            lora_base = lora_base if lora_base is not None else model_path
+
             self.lora_path = lora_path
             if llama_cpp.llama_apply_lora_from_file(
                 self.ctx,
-                self.lora_path.encode("utf-8"),
-                self.model_path.encode("utf-8"),
+                lora_path.encode("utf-8"),
+                lora_base.encode("utf-8"),
                 llama_cpp.c_int(self.n_threads),
             ):
-                raise RuntimeError(f"Failed to apply LoRA from path: {self.lora_path}")
+                raise RuntimeError(f"Failed to apply LoRA from lora path: {lora_path} to base path: {lora_base}")
 
         if self.verbose:
             print(llama_cpp.llama_print_system_info().decode("utf-8"), file=sys.stderr)
@@ -815,6 +822,7 @@ def __getstate__(self):
             last_n_tokens_size=self.last_n_tokens_size,
             n_batch=self.n_batch,
             n_threads=self.n_threads,
+            lora_base=self.lora_base,
             lora_path=self.lora_path,
         )
 
@@ -833,6 +841,7 @@ def __setstate__(self, state):
             n_threads=state["n_threads"],
             n_batch=state["n_batch"],
             last_n_tokens_size=state["last_n_tokens_size"],
+            lora_base=state["lora_base"],
             lora_path=state["lora_path"],
             verbose=state["verbose"],
         )