KohyaSS/networks/resize_lora.py

# Convert LoRA to different rank approximation (should only be used to go to lower rank)
# This code is based off the extract_lora_from_models.py file which is based on https://github.com/cloneofsimo/lora/blob/develop/lora_diffusion/cli_svd.py
# Thanks to cloneofsimo and kohya

import argparse
import os
import torch
from safetensors.torch import load_file, save_file, safe_open
from tqdm import tqdm
from library import train_util, model_util


def load_state_dict(file_name, dtype):
  if model_util.is_safetensors(file_name):
    sd = load_file(file_name)
    with safe_open(file_name, framework="pt") as f:
      metadata = f.metadata()
  else:
    sd = torch.load(file_name, map_location='cpu')
    metadata = None

  for key in list(sd.keys()):
    if type(sd[key]) == torch.Tensor:
      sd[key] = sd[key].to(dtype)

  return sd, metadata


def save_to_file(file_name, model, state_dict, dtype, metadata):
  if dtype is not None:
    for key in list(state_dict.keys()):
      if type(state_dict[key]) == torch.Tensor:
        state_dict[key] = state_dict[key].to(dtype)

  if model_util.is_safetensors(file_name):
    save_file(model, file_name, metadata)
  else:
    torch.save(model, file_name)


def resize_lora_model(lora_sd, new_rank, save_dtype, device):
  network_alpha = None
  network_dim = None

  CLAMP_QUANTILE = 0.99

  # Extract loaded lora dim and alpha
  for key, value in lora_sd.items():
    if network_alpha is None and 'alpha' in key:
      network_alpha = value
    if network_dim is None and 'lora_down' in key and len(value.size()) == 2:
      network_dim = value.size()[0]
    if network_alpha is not None and network_dim is not None:
      break
    if network_alpha is None:
      network_alpha = network_dim

  scale = network_alpha/network_dim
  new_alpha = float(scale*new_rank)  # calculate new alpha from scale

  print(f"old dimension: {network_dim}, old alpha: {network_alpha}, new alpha: {new_alpha}")

  lora_down_weight = None
  lora_up_weight = None

  o_lora_sd = lora_sd.copy()
  block_down_name = None
  block_up_name = None

  print("resizing lora...")
  with torch.no_grad():
    for key, value in tqdm(lora_sd.items()):
      if 'lora_down' in key:
        block_down_name = key.split(".")[0]
        lora_down_weight = value
      if 'lora_up' in key:
        block_up_name = key.split(".")[0]
        lora_up_weight = value

      weights_loaded = (lora_down_weight is not None and lora_up_weight is not None)

      if (block_down_name == block_up_name) and weights_loaded:

        conv2d = (len(lora_down_weight.size()) == 4)

        if conv2d:
          lora_down_weight = lora_down_weight.squeeze()
          lora_up_weight = lora_up_weight.squeeze()

        if device:
          org_device = lora_up_weight.device
          lora_up_weight = lora_up_weight.to(args.device)
          lora_down_weight = lora_down_weight.to(args.device)

        full_weight_matrix = torch.matmul(lora_up_weight, lora_down_weight)

        U, S, Vh = torch.linalg.svd(full_weight_matrix)

        U = U[:, :new_rank]
        S = S[:new_rank]
        U = U @ torch.diag(S)

        Vh = Vh[:new_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 conv2d:
          U = U.unsqueeze(2).unsqueeze(3)
          Vh = Vh.unsqueeze(2).unsqueeze(3)

        if args.device:
          U = U.to(org_device)
          Vh = Vh.to(org_device)

        o_lora_sd[block_down_name + "." + "lora_down.weight"] = Vh.to(save_dtype).contiguous()
        o_lora_sd[block_up_name + "." + "lora_up.weight"] = U.to(save_dtype).contiguous()
        o_lora_sd[block_up_name + "." "alpha"] = torch.tensor(new_alpha).to(save_dtype)

        block_down_name = None
        block_up_name = None
        lora_down_weight = None
        lora_up_weight = None
        weights_loaded = False

  print("resizing complete")
  return o_lora_sd, network_dim, new_alpha


def resize(args):

  def str_to_dtype(p):
    if p == 'float':
      return torch.float
    if p == 'fp16':
      return torch.float16
    if p == 'bf16':
      return torch.bfloat16
    return None

  merge_dtype = str_to_dtype('float')  # matmul method above only seems to work in float32
  save_dtype = str_to_dtype(args.save_precision)
  if save_dtype is None:
    save_dtype = merge_dtype

  print("loading Model...")
  lora_sd, metadata = load_state_dict(args.model, merge_dtype)

  print("resizing rank...")
  state_dict, old_dim, new_alpha = resize_lora_model(lora_sd, args.new_rank, save_dtype, args.device)

  # update metadata
  if metadata is None:
    metadata = {}

  comment = metadata.get("ss_training_comment", "")
  metadata["ss_training_comment"] = f"dimension is resized from {old_dim} to {args.new_rank}; {comment}"
  metadata["ss_network_dim"] = str(args.new_rank)
  metadata["ss_network_alpha"] = str(new_alpha)

  model_hash, legacy_hash = train_util.precalculate_safetensors_hashes(state_dict, metadata)
  metadata["sshs_model_hash"] = model_hash
  metadata["sshs_legacy_hash"] = legacy_hash

  print(f"saving model to: {args.save_to}")
  save_to_file(args.save_to, state_dict, state_dict, save_dtype, metadata)


if __name__ == '__main__':
  parser = argparse.ArgumentParser()

  parser.add_argument("--save_precision", type=str, default=None,
                      choices=[None, "float", "fp16", "bf16"], help="precision in saving, float if omitted / 保存時の精度、未指定時はfloat")
  parser.add_argument("--new_rank", type=int, default=4,
                      help="Specify rank of output LoRA / 出力するLoRAのrank (dim)")
  parser.add_argument("--save_to", type=str, default=None,
                      help="destination file name: ckpt or safetensors file / 保存先のファイル名、ckptまたはsafetensors")
  parser.add_argument("--model", type=str, default=None,
                      help="LoRA model to resize at to new rank: ckpt or safetensors file / 読み込むLoRAモデル、ckptまたはsafetensors")
  parser.add_argument("--device", type=str, default=None, help="device to use, cuda for GPU / 計算を行うデバイス、cuda でGPUを使う")

  args = parser.parse_args()
  resize(args)