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"""
This script demonstrates how to extract a LoRA checkpoint from a fully finetuned model with the CogVideoX model.
To make it work for other models:
* Change the model class. Here we use `CogVideoXTransformer3DModel`. For Flux, it would be `FluxTransformer2DModel`,
for example. (TODO: more reason to add `AutoModel`).
* Spply path to the base checkpoint via `base_ckpt_path`.
* Supply path to the fully fine-tuned checkpoint via `--finetune_ckpt_path`.
* Change the `--rank` as needed.
Example usage:
```bash
python extract_lora_from_model.py \
--base_ckpt_path=THUDM/CogVideoX-5b \
--finetune_ckpt_path=finetrainers/cakeify-v0 \
--lora_out_path=cakeify_lora.safetensors
```
Script is adapted from
https://github.com/Stability-AI/stability-ComfyUI-nodes/blob/001154622564b17223ce0191803c5fff7b87146c/control_lora_create.py
"""
import argparse
import torch
from safetensors.torch import save_file
from tqdm.auto import tqdm
from diffusers import CogVideoXTransformer3DModel
RANK = 64
CLAMP_QUANTILE = 0.99
# Comes from
# https://github.com/Stability-AI/stability-ComfyUI-nodes/blob/001154622564b17223ce0191803c5fff7b87146c/control_lora_create.py#L9
def extract_lora(diff, rank):
# Important to use CUDA otherwise, very slow!
if torch.cuda.is_available():
diff = diff.to("cuda")
is_conv2d = len(diff.shape) == 4
kernel_size = None if not is_conv2d else diff.size()[2:4]
is_conv2d_3x3 = is_conv2d and kernel_size != (1, 1)
out_dim, in_dim = diff.size()[0:2]
rank = min(rank, in_dim, out_dim)
if is_conv2d:
if is_conv2d_3x3:
diff = diff.flatten(start_dim=1)
else:
diff = diff.squeeze()
U, S, Vh = torch.linalg.svd(diff.float())
U = U[:, :rank]
S = S[:rank]
U = U @ torch.diag(S)
Vh = Vh[:rank, :]
dist = torch.cat([U.flatten(), Vh.flatten()])
hi_val = torch.quantile(dist, CLAMP_QUANTILE)
low_val = -hi_val
U = U.clamp(low_val, hi_val)
Vh = Vh.clamp(low_val, hi_val)
if is_conv2d:
U = U.reshape(out_dim, rank, 1, 1)
Vh = Vh.reshape(rank, in_dim, kernel_size[0], kernel_size[1])
return (U.cpu(), Vh.cpu())
def parse_args():
parser = argparse.ArgumentParser()
parser.add_argument(
"--base_ckpt_path",
default=None,
type=str,
required=True,
help="Base checkpoint path from which the model was finetuned. Can be a model ID on the Hub.",
)
parser.add_argument(
"--base_subfolder",
default="transformer",
type=str,
help="subfolder to load the base checkpoint from if any.",
)
parser.add_argument(
"--finetune_ckpt_path",
default=None,
type=str,
required=True,
help="Fully fine-tuned checkpoint path. Can be a model ID on the Hub.",
)
parser.add_argument(
"--finetune_subfolder",
default=None,
type=str,
help="subfolder to load the fulle finetuned checkpoint from if any.",
)
parser.add_argument("--rank", default=64, type=int)
parser.add_argument("--lora_out_path", default=None, type=str, required=True)
args = parser.parse_args()
if not args.lora_out_path.endswith(".safetensors"):
raise ValueError("`lora_out_path` must end with `.safetensors`.")
return args
@torch.no_grad()
def main(args):
model_finetuned = CogVideoXTransformer3DModel.from_pretrained(
args.finetune_ckpt_path, subfolder=args.finetune_subfolder, torch_dtype=torch.bfloat16
)
state_dict_ft = model_finetuned.state_dict()
# Change the `subfolder` as needed.
base_model = CogVideoXTransformer3DModel.from_pretrained(
args.base_ckpt_path, subfolder=args.base_subfolder, torch_dtype=torch.bfloat16
)
state_dict = base_model.state_dict()
output_dict = {}
for k in tqdm(state_dict, desc="Extracting LoRA..."):
original_param = state_dict[k]
finetuned_param = state_dict_ft[k]
if len(original_param.shape) >= 2:
diff = finetuned_param.float() - original_param.float()
out = extract_lora(diff, RANK)
name = k
if name.endswith(".weight"):
name = name[: -len(".weight")]
down_key = "{}.lora_A.weight".format(name)
up_key = "{}.lora_B.weight".format(name)
output_dict[up_key] = out[0].contiguous().to(finetuned_param.dtype)
output_dict[down_key] = out[1].contiguous().to(finetuned_param.dtype)
prefix = "transformer" if "transformer" in base_model.__class__.__name__.lower() else "unet"
output_dict = {f"{prefix}.{k}": v for k, v in output_dict.items()}
save_file(output_dict, args.lora_out_path)
print(f"LoRA saved and it contains {len(output_dict)} keys.")
if __name__ == "__main__":
args = parse_args()
main(args)
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