support full-parameter PPO

Former-commit-id: 4af967d69475e1c9fdf1a7983cd6b83bd431abff

src/llmtuner/model/utils.py

@@ -1,17 +1,89 @@
 import torch
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, Set, Tuple
+from typing import TYPE_CHECKING, Any, Dict, List, Literal, Optional, Set, Tuple, Union
+
+from transformers.utils import cached_file
+from transformers.trainer import WEIGHTS_NAME, SAFE_WEIGHTS_NAME
 
 from llmtuner.extras.constants import LAYERNORM_NAMES
 from llmtuner.extras.logging import get_logger
+from llmtuner.hparams import ModelArguments, FinetuningArguments
+from llmtuner.model import load_model_and_tokenizer
 
 if TYPE_CHECKING:
     from transformers.modeling_utils import PreTrainedModel
-    from llmtuner.hparams import ModelArguments, DataArguments, FinetuningArguments
+    from trl import AutoModelForCausalLMWithValueHead
+    from llmtuner.hparams import DataArguments
 
 
 logger = get_logger(__name__)
 
 
+def create_ref_model(
+    model_args: "ModelArguments",
+    finetuning_args: "FinetuningArguments",
+    stage: Literal["ppo", "dpo"]
+) -> Union["PreTrainedModel", "AutoModelForCausalLMWithValueHead"]:
+    r"""
+    Creates reference model for PPO/DPO training. Evaluation mode is not supported.
+
+    The valuehead parameter is randomly initialized since it is useless for PPO training.
+    """
+    if finetuning_args.ref_model is not None:
+        ref_model_args_dict = model_args.to_dict()
+        ref_model_args_dict.update(dict(
+            model_name_or_path=finetuning_args.ref_model,
+            checkpoint_dir=finetuning_args.ref_model_checkpoint,
+            quantization_bit=finetuning_args.ref_model_quantization_bit
+        ))
+        ref_model_args = ModelArguments(**ref_model_args_dict)
+        ref_finetuning_args = FinetuningArguments(finetuning_type="lora")
+        ref_model, _ = load_model_and_tokenizer(ref_model_args, ref_finetuning_args, is_trainable=False, stage=stage)
+        logger.info("Created reference model from {}".format(finetuning_args.ref_model))
+    else:
+        if finetuning_args.finetuning_type == "lora":
+            ref_model = None
+        else:
+            ref_model, _ = load_model_and_tokenizer(model_args, finetuning_args, is_trainable=False, stage=stage)
+            logger.info("Created reference model from the model itself.")
+
+    return ref_model
+
+
+def create_reward_model(
+    model: "AutoModelForCausalLMWithValueHead",
+    model_args: "ModelArguments",
+    finetuning_args: "FinetuningArguments"
+) -> "AutoModelForCausalLMWithValueHead":
+    r"""
+    Creates reward model for PPO training.
+    """
+    if finetuning_args.reward_model_type == "lora":
+        model.pretrained_model.load_adapter(finetuning_args.reward_model, "reward")
+        for name, param in model.named_parameters(): # https://github.com/huggingface/peft/issues/1090
+            if "default" in name:
+                param.data = param.data.to(torch.float32) # trainable params should in fp32
+        vhead_params = load_valuehead_params(model_args.checkpoint_dir[-1], model_args)
+        assert vhead_params is not None, "Reward model is not correctly loaded."
+        model.register_buffer("reward_head_weight", vhead_params["v_head.summary.weight"], persistent=False)
+        model.register_buffer("reward_head_bias", vhead_params["v_head.summary.bias"], persistent=False)
+        model.register_buffer("default_head_weight", torch.zeros_like(vhead_params["v_head.summary.weight"]), persistent=False)
+        model.register_buffer("default_head_bias", torch.zeros_like(vhead_params["v_head.summary.bias"]), persistent=False)
+        logger.info("Loaded adapter weights of reward model from {}".format(finetuning_args.reward_model))
+        return None
+    else:
+        reward_model_args_dict = model_args.to_dict()
+        reward_model_args_dict.update(dict(
+            model_name_or_path=finetuning_args.reward_model,
+            checkpoint_dir=finetuning_args.reward_model_checkpoint,
+            quantization_bit=finetuning_args.reward_model_quantization_bit
+        ))
+        reward_model_args = ModelArguments(**reward_model_args_dict)
+        reward_finetuning_args = FinetuningArguments(finetuning_type="lora")
+        reward_model, _ = load_model_and_tokenizer(reward_model_args, reward_finetuning_args, is_trainable=False, stage="ppo")
+        logger.info("Load full weights of reward model from {}".format(finetuning_args.reward_model))
+        return reward_model
+
+
 def dispatch_model(model: "PreTrainedModel") -> "PreTrainedModel":
     r"""
     Dispatches a pre-trained model to GPUs with balanced memory.
@@ -41,6 +113,9 @@ def find_all_linear_modules(
     model: "PreTrainedModel",
     quantization_bit: Optional[int] = None
 ) -> List[str]:
+    r"""
+    Finds all available modules to apply lora.
+    """
     if quantization_bit is not None:
         import bitsandbytes as bnb
         linear_cls = bnb.nn.Linear4bit if quantization_bit == 4 else bnb.nn.Linear8bitLt
@@ -76,6 +151,32 @@ def generate_model_card(
     }
 
 
+def load_valuehead_params(
+    path_or_repo_id: str,
+    model_args: "ModelArguments"
+) -> Dict[str, torch.Tensor]:
+    r"""
+    Loads value head parameters from Hugging Face Hub or local disk.
+
+    Returns: dict with keys `v_head.summary.weight` and `v_head.summary.bias`.
+    """
+    kwargs = {
+        "path_or_repo_id": path_or_repo_id,
+        "cache_dir": model_args.cache_dir,
+        "token": model_args.hf_hub_token
+    }
+    try:
+        vhead_file = cached_file(filename=WEIGHTS_NAME, **kwargs)
+    except:
+        try:
+            vhead_file = cached_file(filename=SAFE_WEIGHTS_NAME, **kwargs)
+        except:
+            logger.warning("Provided path ({}) does not contain valuehead weights.".format(path_or_repo_id))
+            return None
+
+    return torch.load(vhead_file, map_location="cpu")
+
+
 def prepare_model_for_training(
     model: "PreTrainedModel",
     finetuning_args: "FinetuningArguments",