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# coding=utf-8
# Copyright 2022 The HuggingFace Inc. team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" PyTorch - Flax general utilities."""
import re
import jax.numpy as jnp
from flax.traverse_util import flatten_dict, unflatten_dict
from jax.random import PRNGKey
from .utils import logging
logger = logging.get_logger(__name__)
def rename_key(key):
regex = r"\w+[.]\d+"
pats = re.findall(regex, key)
for pat in pats:
key = key.replace(pat, "_".join(pat.split(".")))
return key
#####################
# PyTorch => Flax #
#####################
# Adapted from https://github.com/huggingface/transformers/blob/c603c80f46881ae18b2ca50770ef65fa4033eacd/src/transformers/modeling_flax_pytorch_utils.py#L69
# and https://github.com/patil-suraj/stable-diffusion-jax/blob/main/stable_diffusion_jax/convert_diffusers_to_jax.py
def rename_key_and_reshape_tensor(pt_tuple_key, pt_tensor, random_flax_state_dict):
"""Rename PT weight names to corresponding Flax weight names and reshape tensor if necessary"""
# conv norm or layer norm
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("scale",)
if (
any("norm" in str_ for str_ in pt_tuple_key)
and (pt_tuple_key[-1] == "bias")
and (pt_tuple_key[:-1] + ("bias",) not in random_flax_state_dict)
and (pt_tuple_key[:-1] + ("scale",) in random_flax_state_dict)
):
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("scale",)
return renamed_pt_tuple_key, pt_tensor
elif pt_tuple_key[-1] in ["weight", "gamma"] and pt_tuple_key[:-1] + ("scale",) in random_flax_state_dict:
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("scale",)
return renamed_pt_tuple_key, pt_tensor
# embedding
if pt_tuple_key[-1] == "weight" and pt_tuple_key[:-1] + ("embedding",) in random_flax_state_dict:
pt_tuple_key = pt_tuple_key[:-1] + ("embedding",)
return renamed_pt_tuple_key, pt_tensor
# conv layer
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("kernel",)
if pt_tuple_key[-1] == "weight" and pt_tensor.ndim == 4:
pt_tensor = pt_tensor.transpose(2, 3, 1, 0)
return renamed_pt_tuple_key, pt_tensor
# linear layer
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("kernel",)
if pt_tuple_key[-1] == "weight":
pt_tensor = pt_tensor.T
return renamed_pt_tuple_key, pt_tensor
# old PyTorch layer norm weight
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("weight",)
if pt_tuple_key[-1] == "gamma":
return renamed_pt_tuple_key, pt_tensor
# old PyTorch layer norm bias
renamed_pt_tuple_key = pt_tuple_key[:-1] + ("bias",)
if pt_tuple_key[-1] == "beta":
return renamed_pt_tuple_key, pt_tensor
return pt_tuple_key, pt_tensor
def convert_pytorch_state_dict_to_flax(pt_state_dict, flax_model, init_key=42):
# Step 1: Convert pytorch tensor to numpy
pt_state_dict = {k: v.numpy() for k, v in pt_state_dict.items()}
# Step 2: Since the model is stateless, get random Flax params
random_flax_params = flax_model.init_weights(PRNGKey(init_key))
random_flax_state_dict = flatten_dict(random_flax_params)
flax_state_dict = {}
# Need to change some parameters name to match Flax names
for pt_key, pt_tensor in pt_state_dict.items():
renamed_pt_key = rename_key(pt_key)
pt_tuple_key = tuple(renamed_pt_key.split("."))
# Correctly rename weight parameters
flax_key, flax_tensor = rename_key_and_reshape_tensor(pt_tuple_key, pt_tensor, random_flax_state_dict)
if flax_key in random_flax_state_dict:
if flax_tensor.shape != random_flax_state_dict[flax_key].shape:
raise ValueError(
f"PyTorch checkpoint seems to be incorrect. Weight {pt_key} was expected to be of shape "
f"{random_flax_state_dict[flax_key].shape}, but is {flax_tensor.shape}."
)
# also add unexpected weight so that warning is thrown
flax_state_dict[flax_key] = jnp.asarray(flax_tensor)
return unflatten_dict(flax_state_dict)
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