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# coding=utf-8
# Copyright 2025 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.
import os
from pickle import UnpicklingError
from typing import Any
import jax
import jax.numpy as jnp
import msgpack.exceptions
from flax.core.frozen_dict import FrozenDict, unfreeze
from flax.serialization import from_bytes, to_bytes
from flax.traverse_util import flatten_dict, unflatten_dict
from huggingface_hub import create_repo, hf_hub_download
from huggingface_hub.utils import (
EntryNotFoundError,
HfHubHTTPError,
RepositoryNotFoundError,
RevisionNotFoundError,
validate_hf_hub_args,
)
from .. import __version__, is_torch_available
from ..utils import (
CONFIG_NAME,
FLAX_WEIGHTS_NAME,
HUGGINGFACE_CO_RESOLVE_ENDPOINT,
WEIGHTS_NAME,
PushToHubMixin,
logging,
)
from .modeling_flax_pytorch_utils import convert_pytorch_state_dict_to_flax
logger = logging.get_logger(__name__)
class FlaxModelMixin(PushToHubMixin):
r"""
Base class for all Flax models.
[`FlaxModelMixin`] takes care of storing the model configuration and provides methods for loading, downloading and
saving models.
- **config_name** ([`str`]) -- Filename to save a model to when calling [`~FlaxModelMixin.save_pretrained`].
"""
config_name = CONFIG_NAME
_automatically_saved_args = ["_diffusers_version", "_class_name", "_name_or_path"]
_flax_internal_args = ["name", "parent", "dtype"]
@classmethod
def _from_config(cls, config, **kwargs):
"""
All context managers that the model should be initialized under go here.
"""
return cls(config, **kwargs)
def _cast_floating_to(self, params: dict | FrozenDict, dtype: jnp.dtype, mask: Any = None) -> Any:
"""
Helper method to cast floating-point values of given parameter `PyTree` to given `dtype`.
"""
# taken from https://github.com/deepmind/jmp/blob/3a8318abc3292be38582794dbf7b094e6583b192/jmp/_src/policy.py#L27
def conditional_cast(param):
if isinstance(param, jnp.ndarray) and jnp.issubdtype(param.dtype, jnp.floating):
param = param.astype(dtype)
return param
if mask is None:
return jax.tree_map(conditional_cast, params)
flat_params = flatten_dict(params)
flat_mask, _ = jax.tree_flatten(mask)
for masked, key in zip(flat_mask, flat_params.keys()):
if masked:
param = flat_params[key]
flat_params[key] = conditional_cast(param)
return unflatten_dict(flat_params)
def to_bf16(self, params: dict | FrozenDict, mask: Any = None):
r"""
Cast the floating-point `params` to `jax.numpy.bfloat16`. This returns a new `params` tree and does not cast
the `params` in place.
This method can be used on a TPU to explicitly convert the model parameters to bfloat16 precision to do full
half-precision training or to save weights in bfloat16 for inference in order to save memory and improve speed.
Arguments:
params (`dict | FrozenDict`):
A `PyTree` of model parameters.
mask (`dict | FrozenDict`):
A `PyTree` with same structure as the `params` tree. The leaves should be booleans. It should be `True`
for params you want to cast, and `False` for those you want to skip.
Examples:
```python
>>> from diffusers import FlaxUNet2DConditionModel
>>> # load model
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5")
>>> # By default, the model parameters will be in fp32 precision, to cast these to bfloat16 precision
>>> params = model.to_bf16(params)
>>> # If you don't want to cast certain parameters (for example layer norm bias and scale)
>>> # then pass the mask as follows
>>> from flax import traverse_util
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5")
>>> flat_params = traverse_util.flatten_dict(params)
>>> mask = {
... path: (path[-2] != ("LayerNorm", "bias") and path[-2:] != ("LayerNorm", "scale"))
... for path in flat_params
... }
>>> mask = traverse_util.unflatten_dict(mask)
>>> params = model.to_bf16(params, mask)
```"""
return self._cast_floating_to(params, jnp.bfloat16, mask)
def to_fp32(self, params: dict | FrozenDict, mask: Any = None):
r"""
Cast the floating-point `params` to `jax.numpy.float32`. This method can be used to explicitly convert the
model parameters to fp32 precision. This returns a new `params` tree and does not cast the `params` in place.
Arguments:
params (`dict | FrozenDict`):
A `PyTree` of model parameters.
mask (`dict | FrozenDict`):
A `PyTree` with same structure as the `params` tree. The leaves should be booleans. It should be `True`
for params you want to cast, and `False` for those you want to skip.
Examples:
```python
>>> from diffusers import FlaxUNet2DConditionModel
>>> # Download model and configuration from huggingface.co
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5")
>>> # By default, the model params will be in fp32, to illustrate the use of this method,
>>> # we'll first cast to fp16 and back to fp32
>>> params = model.to_f16(params)
>>> # now cast back to fp32
>>> params = model.to_fp32(params)
```"""
return self._cast_floating_to(params, jnp.float32, mask)
def to_fp16(self, params: dict | FrozenDict, mask: Any = None):
r"""
Cast the floating-point `params` to `jax.numpy.float16`. This returns a new `params` tree and does not cast the
`params` in place.
This method can be used on a GPU to explicitly convert the model parameters to float16 precision to do full
half-precision training or to save weights in float16 for inference in order to save memory and improve speed.
Arguments:
params (`dict | FrozenDict`):
A `PyTree` of model parameters.
mask (`dict | FrozenDict`):
A `PyTree` with same structure as the `params` tree. The leaves should be booleans. It should be `True`
for params you want to cast, and `False` for those you want to skip.
Examples:
```python
>>> from diffusers import FlaxUNet2DConditionModel
>>> # load model
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5")
>>> # By default, the model params will be in fp32, to cast these to float16
>>> params = model.to_fp16(params)
>>> # If you want don't want to cast certain parameters (for example layer norm bias and scale)
>>> # then pass the mask as follows
>>> from flax import traverse_util
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5")
>>> flat_params = traverse_util.flatten_dict(params)
>>> mask = {
... path: (path[-2] != ("LayerNorm", "bias") and path[-2:] != ("LayerNorm", "scale"))
... for path in flat_params
... }
>>> mask = traverse_util.unflatten_dict(mask)
>>> params = model.to_fp16(params, mask)
```"""
return self._cast_floating_to(params, jnp.float16, mask)
def init_weights(self, rng: jax.Array) -> dict:
raise NotImplementedError(f"init_weights method has to be implemented for {self}")
@classmethod
@validate_hf_hub_args
def from_pretrained(
cls,
pretrained_model_name_or_path: str | os.PathLike,
dtype: jnp.dtype = jnp.float32,
*model_args,
**kwargs,
):
r"""
Instantiate a pretrained Flax model from a pretrained model configuration.
Parameters:
pretrained_model_name_or_path (`str` or `os.PathLike`):
Can be either:
- A string, the *model id* (for example `stable-diffusion-v1-5/stable-diffusion-v1-5`) of a
pretrained model hosted on the Hub.
- A path to a *directory* (for example `./my_model_directory`) containing the model weights saved
using [`~FlaxModelMixin.save_pretrained`].
dtype (`jax.numpy.dtype`, *optional*, defaults to `jax.numpy.float32`):
The data type of the computation. Can be one of `jax.numpy.float32`, `jax.numpy.float16` (on GPUs) and
`jax.numpy.bfloat16` (on TPUs).
This can be used to enable mixed-precision training or half-precision inference on GPUs or TPUs. If
specified, all the computation will be performed with the given `dtype`.
> [!TIP] > This only specifies the dtype of the *computation* and does not influence the dtype of model
> parameters. > > If you wish to change the dtype of the model parameters, see
[`~FlaxModelMixin.to_fp16`] and > [`~FlaxModelMixin.to_bf16`].
model_args (sequence of positional arguments, *optional*):
All remaining positional arguments are passed to the underlying model's `__init__` method.
cache_dir (`str | os.PathLike`, *optional*):
Path to a directory where a downloaded pretrained model configuration is cached if the standard cache
is not used.
force_download (`bool`, *optional*, defaults to `False`):
Whether or not to force the (re-)download of the model weights and configuration files, overriding the
cached versions if they exist.
proxies (`dict[str, str]`, *optional*):
A dictionary of proxy servers to use by protocol or endpoint, for example, `{'http': 'foo.bar:3128',
'http://hostname': 'foo.bar:4012'}`. The proxies are used on each request.
local_files_only(`bool`, *optional*, defaults to `False`):
Whether to only load local model weights and configuration files or not. If set to `True`, the model
won't be downloaded from the Hub.
revision (`str`, *optional*, defaults to `"main"`):
The specific model version to use. It can be a branch name, a tag name, a commit id, or any identifier
allowed by Git.
from_pt (`bool`, *optional*, defaults to `False`):
Load the model weights from a PyTorch checkpoint save file.
kwargs (remaining dictionary of keyword arguments, *optional*):
Can be used to update the configuration object (after it is loaded) and initiate the model (for
example, `output_attentions=True`). Behaves differently depending on whether a `config` is provided or
automatically loaded:
- If a configuration is provided with `config`, `kwargs` are directly passed to the underlying
model's `__init__` method (we assume all relevant updates to the configuration have already been
done).
- If a configuration is not provided, `kwargs` are first passed to the configuration class
initialization function [`~ConfigMixin.from_config`]. Each key of the `kwargs` that corresponds
to a configuration attribute is used to override said attribute with the supplied `kwargs` value.
Remaining keys that do not correspond to any configuration attribute are passed to the underlying
model's `__init__` function.
Examples:
```python
>>> from diffusers import FlaxUNet2DConditionModel
>>> # Download model and configuration from huggingface.co and cache.
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5")
>>> # Model was saved using *save_pretrained('./test/saved_model/')* (for example purposes, not runnable).
>>> model, params = FlaxUNet2DConditionModel.from_pretrained("./test/saved_model/")
```
If you get the error message below, you need to finetune the weights for your downstream task:
```bash
Some weights of UNet2DConditionModel were not initialized from the model checkpoint at stable-diffusion-v1-5/stable-diffusion-v1-5 and are newly initialized because the shapes did not match:
- conv_in.weight: found shape torch.Size([320, 4, 3, 3]) in the checkpoint and torch.Size([320, 9, 3, 3]) in the model instantiated
You should probably TRAIN this model on a down-stream task to be able to use it for predictions and inference.
```
"""
logger.warning(
"Flax classes are deprecated and will be removed in Diffusers v1.0.0. We "
"recommend migrating to PyTorch classes or pinning your version of Diffusers."
)
config = kwargs.pop("config", None)
cache_dir = kwargs.pop("cache_dir", None)
force_download = kwargs.pop("force_download", False)
from_pt = kwargs.pop("from_pt", False)
proxies = kwargs.pop("proxies", None)
local_files_only = kwargs.pop("local_files_only", False)
token = kwargs.pop("token", None)
revision = kwargs.pop("revision", None)
subfolder = kwargs.pop("subfolder", None)
user_agent = {
"diffusers": __version__,
"file_type": "model",
"framework": "flax",
}
# Load config if we don't provide one
if config is None:
config, unused_kwargs = cls.load_config(
pretrained_model_name_or_path,
cache_dir=cache_dir,
return_unused_kwargs=True,
force_download=force_download,
proxies=proxies,
local_files_only=local_files_only,
token=token,
revision=revision,
subfolder=subfolder,
**kwargs,
)
model, model_kwargs = cls.from_config(config, dtype=dtype, return_unused_kwargs=True, **unused_kwargs)
# Load model
pretrained_path_with_subfolder = (
pretrained_model_name_or_path
if subfolder is None
else os.path.join(pretrained_model_name_or_path, subfolder)
)
if os.path.isdir(pretrained_path_with_subfolder):
if from_pt:
if not os.path.isfile(os.path.join(pretrained_path_with_subfolder, WEIGHTS_NAME)):
raise EnvironmentError(
f"Error no file named {WEIGHTS_NAME} found in directory {pretrained_path_with_subfolder} "
)
model_file = os.path.join(pretrained_path_with_subfolder, WEIGHTS_NAME)
elif os.path.isfile(os.path.join(pretrained_path_with_subfolder, FLAX_WEIGHTS_NAME)):
# Load from a Flax checkpoint
model_file = os.path.join(pretrained_path_with_subfolder, FLAX_WEIGHTS_NAME)
# Check if pytorch weights exist instead
elif os.path.isfile(os.path.join(pretrained_path_with_subfolder, WEIGHTS_NAME)):
raise EnvironmentError(
f"{WEIGHTS_NAME} file found in directory {pretrained_path_with_subfolder}. Please load the model"
" using `from_pt=True`."
)
else:
raise EnvironmentError(
f"Error no file named {FLAX_WEIGHTS_NAME} or {WEIGHTS_NAME} found in directory "
f"{pretrained_path_with_subfolder}."
)
else:
try:
model_file = hf_hub_download(
pretrained_model_name_or_path,
filename=FLAX_WEIGHTS_NAME if not from_pt else WEIGHTS_NAME,
cache_dir=cache_dir,
force_download=force_download,
proxies=proxies,
local_files_only=local_files_only,
token=token,
user_agent=user_agent,
subfolder=subfolder,
revision=revision,
)
except RepositoryNotFoundError:
raise EnvironmentError(
f"{pretrained_model_name_or_path} is not a local folder and is not a valid model identifier "
"listed on 'https://huggingface.co/models'\nIf this is a private repository, make sure to pass a "
"token having permission to this repo with `token` or log in with `hf auth login`."
)
except RevisionNotFoundError:
raise EnvironmentError(
f"{revision} is not a valid git identifier (branch name, tag name or commit id) that exists for "
"this model name. Check the model page at "
f"'https://huggingface.co/{pretrained_model_name_or_path}' for available revisions."
)
except EntryNotFoundError:
raise EnvironmentError(
f"{pretrained_model_name_or_path} does not appear to have a file named {FLAX_WEIGHTS_NAME}."
)
except HfHubHTTPError as err:
raise EnvironmentError(
f"There was a specific connection error when trying to load {pretrained_model_name_or_path}:\n"
f"{err}"
)
except ValueError:
raise EnvironmentError(
f"We couldn't connect to '{HUGGINGFACE_CO_RESOLVE_ENDPOINT}' to load this model, couldn't find it"
f" in the cached files and it looks like {pretrained_model_name_or_path} is not the path to a"
f" directory containing a file named {FLAX_WEIGHTS_NAME} or {WEIGHTS_NAME}.\nCheckout your"
" internet connection or see how to run the library in offline mode at"
" 'https://huggingface.co/docs/transformers/installation#offline-mode'."
)
except EnvironmentError:
raise EnvironmentError(
f"Can't load the model for '{pretrained_model_name_or_path}'. If you were trying to load it from "
"'https://huggingface.co/models', make sure you don't have a local directory with the same name. "
f"Otherwise, make sure '{pretrained_model_name_or_path}' is the correct path to a directory "
f"containing a file named {FLAX_WEIGHTS_NAME} or {WEIGHTS_NAME}."
)
if from_pt:
if is_torch_available():
from .modeling_utils import load_state_dict
else:
raise EnvironmentError(
"Can't load the model in PyTorch format because PyTorch is not installed. "
"Please, install PyTorch or use native Flax weights."
)
# Step 1: Get the pytorch file
pytorch_model_file = load_state_dict(model_file)
# Step 2: Convert the weights
state = convert_pytorch_state_dict_to_flax(pytorch_model_file, model)
else:
try:
with open(model_file, "rb") as state_f:
state = from_bytes(cls, state_f.read())
except (UnpicklingError, msgpack.exceptions.ExtraData) as e:
try:
with open(model_file) as f:
if f.read().startswith("version"):
raise OSError(
"You seem to have cloned a repository without having git-lfs installed. Please"
" install git-lfs and run `git lfs install` followed by `git lfs pull` in the"
" folder you cloned."
)
else:
raise ValueError from e
except (UnicodeDecodeError, ValueError):
raise EnvironmentError(f"Unable to convert {model_file} to Flax deserializable object. ")
# make sure all arrays are stored as jnp.ndarray
# NOTE: This is to prevent a bug this will be fixed in Flax >= v0.3.4:
# https://github.com/google/flax/issues/1261
state = jax.tree_util.tree_map(lambda x: jax.device_put(x, jax.local_devices(backend="cpu")[0]), state)
# flatten dicts
state = flatten_dict(state)
params_shape_tree = jax.eval_shape(model.init_weights, rng=jax.random.PRNGKey(0))
required_params = set(flatten_dict(unfreeze(params_shape_tree)).keys())
shape_state = flatten_dict(unfreeze(params_shape_tree))
missing_keys = required_params - set(state.keys())
unexpected_keys = set(state.keys()) - required_params
if missing_keys:
logger.warning(
f"The checkpoint {pretrained_model_name_or_path} is missing required keys: {missing_keys}. "
"Make sure to call model.init_weights to initialize the missing weights."
)
cls._missing_keys = missing_keys
for key in state.keys():
if key in shape_state and state[key].shape != shape_state[key].shape:
raise ValueError(
f"Trying to load the pretrained weight for {key} failed: checkpoint has shape "
f"{state[key].shape} which is incompatible with the model shape {shape_state[key].shape}. "
)
# remove unexpected keys to not be saved again
for unexpected_key in unexpected_keys:
del state[unexpected_key]
if len(unexpected_keys) > 0:
logger.warning(
f"Some weights of the model checkpoint at {pretrained_model_name_or_path} were not used when"
f" initializing {model.__class__.__name__}: {unexpected_keys}\n- This IS expected if you are"
f" initializing {model.__class__.__name__} from the checkpoint of a model trained on another task or"
" with another architecture."
)
else:
logger.info(f"All model checkpoint weights were used when initializing {model.__class__.__name__}.\n")
if len(missing_keys) > 0:
logger.warning(
f"Some weights of {model.__class__.__name__} were not initialized from the model checkpoint at"
f" {pretrained_model_name_or_path} and are newly initialized: {missing_keys}\nYou should probably"
" TRAIN this model on a down-stream task to be able to use it for predictions and inference."
)
else:
logger.info(
f"All the weights of {model.__class__.__name__} were initialized from the model checkpoint at"
f" {pretrained_model_name_or_path}.\nIf your task is similar to the task the model of the checkpoint"
f" was trained on, you can already use {model.__class__.__name__} for predictions without further"
" training."
)
return model, unflatten_dict(state)
def save_pretrained(
self,
save_directory: str | os.PathLike,
params: dict | FrozenDict,
is_main_process: bool = True,
push_to_hub: bool = False,
**kwargs,
):
"""
Save a model and its configuration file to a directory so that it can be reloaded using the
[`~FlaxModelMixin.from_pretrained`] class method.
Arguments:
save_directory (`str` or `os.PathLike`):
Directory to save a model and its configuration file to. Will be created if it doesn't exist.
params (`dict | FrozenDict`):
A `PyTree` of model parameters.
is_main_process (`bool`, *optional*, defaults to `True`):
Whether the process calling this is the main process or not. Useful during distributed training and you
need to call this function on all processes. In this case, set `is_main_process=True` only on the main
process to avoid race conditions.
push_to_hub (`bool`, *optional*, defaults to `False`):
Whether or not to push your model to the Hugging Face model hub after saving it. You can specify the
repository you want to push to with `repo_id` (will default to the name of `save_directory` in your
namespace).
kwargs (`dict[str, Any]`, *optional*):
Additional key word arguments passed along to the [`~utils.PushToHubMixin.push_to_hub`] method.
"""
if os.path.isfile(save_directory):
logger.error(f"Provided path ({save_directory}) should be a directory, not a file")
return
os.makedirs(save_directory, exist_ok=True)
if push_to_hub:
commit_message = kwargs.pop("commit_message", None)
private = kwargs.pop("private", None)
create_pr = kwargs.pop("create_pr", False)
token = kwargs.pop("token", None)
repo_id = kwargs.pop("repo_id", save_directory.split(os.path.sep)[-1])
repo_id = create_repo(repo_id, exist_ok=True, private=private, token=token).repo_id
model_to_save = self
# Attach architecture to the config
# Save the config
if is_main_process:
model_to_save.save_config(save_directory)
# save model
output_model_file = os.path.join(save_directory, FLAX_WEIGHTS_NAME)
with open(output_model_file, "wb") as f:
model_bytes = to_bytes(params)
f.write(model_bytes)
logger.info(f"Model weights saved in {output_model_file}")
if push_to_hub:
self._upload_folder(
save_directory,
repo_id,
token=token,
commit_message=commit_message,
create_pr=create_pr,
)