"""Implements the ReLoRA training procedure from https://arxiv.org/abs/2307.05695, minus the initial full fine-tune.""" import glob import json import logging import os.path import shutil from pathlib import Path from typing import Dict, List, Sequence import bitsandbytes as bnb import peft import safetensors.torch as st import torch from huggingface_hub import snapshot_download from torch.optim.lr_scheduler import LRScheduler from torch.optim.optimizer import Optimizer from transformers import ( TrainerCallback, TrainerControl, TrainerState, TrainingArguments, ) from transformers.trainer_utils import PREFIX_CHECKPOINT_DIR from axolotl.utils.dict import DictDefault from axolotl.utils.distributed import is_main_process LOG = logging.getLogger("axolotl.relora") def reset_optimizer(optimizer: torch.optim.Optimizer): for group in optimizer.param_groups: for param in group["params"]: param_state = optimizer.state[param] for key in param_state: if "qmap" in key: continue if key == "step" and isinstance(param_state[key], int): param_state[key] = 0 else: param_state[key] = torch.zeros_like(param_state[key]) class ReLoRACallback(TrainerCallback): """Callback to merge LoRA weights into the base model and save full-weight checkpoints""" def __init__(self, cfg: DictDefault): self.relora_steps = cfg.relora_steps self.cpu_offload = cfg.relora_cpu_offload self.quantized = cfg.load_in_4bit or cfg.load_in_8bit self.last_full_model = cfg.base_model self.resume_from_checkpoint = cfg.resume_from_checkpoint if not os.path.exists(self.last_full_model): self.last_full_model = str(Path(snapshot_download(cfg.base_model))) assert os.path.exists( self.last_full_model ), "for ReLORA base_model must be a local path" self.num_lora_restarts = 0 self.need_full_save = False def on_train_begin( self, _args: TrainingArguments, _state: TrainerState, control: TrainerControl, model: peft.LoraModel, **_kwargs, ): if self.resume_from_checkpoint: weight_path = os.path.join(self.resume_from_checkpoint, "relora") if not os.path.exists(weight_path): LOG.warning( "Resuming ReLoRA from checkpoint, but no full-weight save found" ) else: LOG.info(f"Loading adjusted base weights from {weight_path}") load_weight_checkpoint(model, weight_path) return control def on_step_begin( self, args: TrainingArguments, state: TrainerState, control: TrainerControl, model: peft.LoraModel, optimizer: torch.optim.Optimizer, **_kwargs, ): if state.global_step > 0 and state.global_step % self.relora_steps == 0: checkpoint_folder = os.path.join( args.output_dir, f"{PREFIX_CHECKPOINT_DIR}-{state.global_step}", "relora", ) with torch.no_grad(): merge_and_save( model, self.last_full_model, checkpoint_folder, reinit=True, quantized=self.quantized, actually_save=is_main_process(), cpu_offload=self.cpu_offload, ) reset_optimizer(optimizer) if self.quantized: self.last_full_model = checkpoint_folder self.num_lora_restarts += 1 return control def on_save( self, args: TrainingArguments, state: TrainerState, control: TrainerControl, model: peft.LoraModel, **_kwargs, ): checkpoint_folder = os.path.join( args.output_dir, f"{PREFIX_CHECKPOINT_DIR}-{state.global_step}", "relora" ) if ( state.global_step >= self.relora_steps and state.global_step % self.relora_steps != 0 ): if self.quantized: if is_main_process() and self.last_full_model != checkpoint_folder: # ensure the latest full parameter save is in the latest checkpoint # folder, so that automatic pruning of checkpoints does not remove it LOG.info(f"moving last full parameter save to {checkpoint_folder}") os.makedirs(checkpoint_folder, exist_ok=True) chunks = glob.glob( f"{self.last_full_model}/model*.safetensors" ) + glob.glob(f"{self.last_full_model}/model*.index.json") for path in chunks: new_path = os.path.abspath(shutil.move(path, checkpoint_folder)) try: os.symlink(new_path, path) except OSError: # probably on windows without permission to symlink pass self.last_full_model = checkpoint_folder else: model.model.save_pretrained(checkpoint_folder, safe_serialization=True) return control def on_log( self, _args: TrainingArguments, _state: TrainerState, control: TrainerControl, logs: Dict[str, float], **_kwargs, ): logs["num_lora_restarts"] = self.num_lora_restarts return control def on_train_end( self, args: TrainingArguments, _state: TrainerState, control: TrainerControl, model: peft.LoraModel, **_kwargs, ): if self.quantized: # perform final merge and save with torch.no_grad(): merge_and_save( model, self.last_full_model, args.output_dir, reinit=False, quantized=self.quantized, actually_save=is_main_process(), cpu_offload=self.cpu_offload, ) # no need to save if unquantized, as finetune.py will call merge_and_unload() return control class ReLoRAScheduler(LRScheduler): """Wraps another scheduler to apply per-lora-restart learning rate warmups.""" def __init__( self, optimizer: Optimizer, inner_schedule: LRScheduler, relora_steps: int, warmup_steps: int, min_lr_scale: float = 0.001, ) -> None: self.inner_schedule = inner_schedule self.relora_steps = relora_steps self.warmup_steps = warmup_steps self.min_lr_scale = min_lr_scale super().__init__(optimizer, inner_schedule.last_epoch, inner_schedule.verbose) def get_lr(self) -> float: self.inner_schedule.last_epoch = self.last_epoch original = self.inner_schedule.get_lr() step = self.last_epoch if step < self.relora_steps: scale = 1 else: cycle_t = min(1.0, (step % self.relora_steps) / self.warmup_steps) scale = cycle_t * (1 - self.min_lr_scale) + self.min_lr_scale if isinstance(original, Sequence): return [lr * scale for lr in original] return original * scale def sharded_paths(path: str, module_names: List[str]) -> Dict[str, str]: model_name = "model.safetensors" if not os.path.exists(str(Path(path) / model_name)) and not os.path.exists( str(Path(path) / f"{model_name}.index.json") ): model_name = "pytorch_model.bin" index_path = str(Path(path) / f"{model_name}.index.json") if os.path.exists(index_path): with open(index_path, "r", encoding="utf-8") as file: data = json.load(file) return data["weight_map"] return {(module_name + ".weight"): model_name for module_name in module_names} def lora_delta_weight(layer: peft.tuners.lora.LoraLayer, device) -> torch.Tensor: if isinstance(layer, (peft.tuners.lora.Linear8bitLt, peft.tuners.lora.Linear4bit)): adapter = layer.active_adapter return ( peft.utils.transpose( layer.lora_B[adapter].weight.detach().to(device) @ layer.lora_A[adapter].weight.detach().to(device), getattr(layer, "fan_in_fan_out", False), ) * layer.scaling[adapter] ) return layer.get_delta_weight().to(device) def find_lora_modules(model: peft.LoraModel) -> Dict[str, peft.tuners.lora.LoraLayer]: modules: Dict[str, peft.tuners.lora.LoraLayer] = {} key_list = [key for key, _ in model.model.named_modules() if "lora" not in key] for key in key_list: try: # pylint: disable=protected-access _parent, target, _target_name = peft.utils._get_submodules(model.model, key) except AttributeError: continue if isinstance(target, peft.tuners.lora.LoraLayer): modules[key] = target return modules def update_weights( target: peft.tuners.lora.LoraLayer, new_weight: torch.Tensor, reinit: bool, device ): if reinit: for adapter_name in target.lora_A: target.reset_lora_parameters(adapter_name) for adapter_name in target.lora_embedding_A: target.reset_lora_parameters(adapter_name) if isinstance(target, peft.tuners.lora.Linear4bit): # This could be faster, but the quantization of Linear4bit weights occurs # when the module is moved from cpu to gpu. Without meddling *too* deeply in # PEFT's innards or maintaining a duplicate of that codepath, this is good # enough for now. target.weight.quant_state = None target.weight.data = new_weight.cpu() target.to(device) elif isinstance(target, peft.tuners.lora.Linear8bitLt): target.weight = bnb.nn.Int8Params(new_weight, requires_grad=False).to(device) else: target.weight.data = new_weight.to(device) def merge_and_save( model: peft.LoraModel, model_src: str, model_dst: str, reinit: bool = False, quantized: bool = False, cpu_offload: bool = False, actually_save: bool = True, ): modules = find_lora_modules(model) if not quantized: for module_name, target in modules.items(): update = target.get_delta_weight(target.active_adapter).detach() target.weight.data += update if reinit: for adapter_name in target.lora_A: target.reset_lora_parameters(adapter_name) for adapter_name in target.lora_embedding_A: target.reset_lora_parameters(adapter_name) return os.makedirs(model_dst, exist_ok=True) shard_paths = sharded_paths(model_src, modules.keys()) out_shard_paths = {} unique_shards = list(set(shard_paths.values())) for shard_path in unique_shards: out_tensors = {} if shard_path.endswith(".safetensors"): in_tensors = st.load_file(str(Path(model_src) / shard_path)) else: in_tensors = torch.load(Path(model_src) / shard_path) if "state_dict" in in_tensors: in_tensors = in_tensors["state_dict"] for module_name, target in modules.items(): key = module_name + ".weight" if key not in shard_paths or shard_paths[key] != shard_path: continue orig_weight = in_tensors[key] old_dev = target.weight.device math_dev = "cpu" if cpu_offload else old_dev delta_weight = lora_delta_weight(target, math_dev) new_weight = orig_weight.to(math_dev) + delta_weight del delta_weight if actually_save: out_tensors[key] = new_weight.half().cpu() update_weights(target, new_weight, reinit=reinit, device=old_dev) if actually_save: out_shard_name = shard_path if out_shard_name.startswith("pytorch_model"): out_shard_name = ( out_shard_name.replace("pytorch_model", "model").rstrip(".bin") + ".safetensors" ) for module_name in in_tensors: if module_name not in out_tensors: out_tensors[module_name] = in_tensors[module_name].half() out_shard_paths[module_name] = out_shard_name shard_fn = str(Path(model_dst) / out_shard_name) LOG.info(f"saving tensors to {shard_fn}") st.save_file(out_tensors, shard_fn, metadata={"format": "pt"}) del in_tensors del out_tensors torch.cuda.empty_cache() if actually_save and len(unique_shards) > 1: with open( str(Path(model_dst, "model.safetensors.index.json")), "w", encoding="utf-8" ) as file: json.dump({"metadata": {}, "weight_map": out_shard_paths}, file) def load_weight_checkpoint(model: peft.LoraModel, checkpoint_path: str): modules = find_lora_modules(model) shard_paths = sharded_paths(checkpoint_path, modules.keys()) unique_shards = list(set(shard_paths.values())) for shard_path in unique_shards: tensors = st.load_file(os.path.join(checkpoint_path, shard_path)) for module_name, target in modules.items(): key = module_name + ".weight" if key not in shard_paths or shard_paths[key] != shard_path: continue new_weight = tensors[key] update_weights( target, new_weight, reinit=False, device=target.weight.device )