File size: 20,404 Bytes
9231ab9
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
# coding=utf-8
# Copyright 2021 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 os
from pickle import UnpicklingError
from typing import Dict, Tuple

import jax
import jax.numpy as jnp
import numpy as np
from flax.serialization import from_bytes
from flax.traverse_util import flatten_dict, unflatten_dict

import transformers

from .utils import logging


logger = logging.get_logger(__name__)


#####################
# PyTorch => Flax #
#####################


def load_pytorch_checkpoint_in_flax_state_dict(
    flax_model, pytorch_checkpoint_path, is_sharded, allow_missing_keys=False
):
    """Load pytorch checkpoints in a flax model"""
    try:
        import torch  # noqa: F401
    except ImportError:
        logger.error(
            "Loading a PyTorch model in Flax, requires both PyTorch and Flax to be installed. Please see"
            " https://pytorch.org/ and https://flax.readthedocs.io/en/latest/installation.html for installation"
            " instructions."
        )
        raise

    if not is_sharded:
        pt_path = os.path.abspath(pytorch_checkpoint_path)
        logger.info(f"Loading PyTorch weights from {pt_path}")

        pt_state_dict = torch.load(pt_path, map_location="cpu")
        logger.info(f"PyTorch checkpoint contains {sum(t.numel() for t in pt_state_dict.values()):,} parameters.")

        flax_state_dict = convert_pytorch_state_dict_to_flax(pt_state_dict, flax_model)
    else:
        # model is sharded and pytorch_checkpoint_path already contains the list of .pt shard files
        flax_state_dict = convert_pytorch_sharded_state_dict_to_flax(pytorch_checkpoint_path, flax_model)
    return flax_state_dict


def rename_key_and_reshape_tensor(
    pt_tuple_key: Tuple[str],
    pt_tensor: np.ndarray,
    random_flax_state_dict: Dict[str, jnp.ndarray],
    model_prefix: str,
) -> (Tuple[str], np.ndarray):
    """Rename PT weight names to corresponding Flax weight names and reshape tensor if necessary"""

    def is_key_or_prefix_key_in_dict(key: Tuple[str]) -> bool:
        """Checks if `key` of `(prefix,) + key` is in random_flax_state_dict"""
        return len(set(random_flax_state_dict) & {key, (model_prefix,) + key}) > 0

    # layer norm
    renamed_pt_tuple_key = pt_tuple_key[:-1] + ("scale",)
    if pt_tuple_key[-1] in ["weight", "gamma"] and is_key_or_prefix_key_in_dict(renamed_pt_tuple_key):
        return renamed_pt_tuple_key, pt_tensor

    # batch norm layer mean
    renamed_pt_tuple_key = pt_tuple_key[:-1] + ("mean",)
    if pt_tuple_key[-1] == "running_mean" and not is_key_or_prefix_key_in_dict(pt_tuple_key):
        return renamed_pt_tuple_key, pt_tensor

    # batch norm layer var
    renamed_pt_tuple_key = pt_tuple_key[:-1] + ("var",)
    if pt_tuple_key[-1] == "running_var" and not is_key_or_prefix_key_in_dict(pt_tuple_key):
        return renamed_pt_tuple_key, pt_tensor

    # embedding
    renamed_pt_tuple_key = pt_tuple_key[:-1] + ("embedding",)
    if pt_tuple_key[-1] == "weight" and is_key_or_prefix_key_in_dict(renamed_pt_tuple_key):
        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 and not is_key_or_prefix_key_in_dict(pt_tuple_key):
        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" and not is_key_or_prefix_key_in_dict(pt_tuple_key):
        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

    # New `weight_norm` from https://github.com/huggingface/transformers/pull/24030
    name = None
    if pt_tuple_key[-3::2] == ("parametrizations", "original0"):
        name = pt_tuple_key[-2] + "_g"
    elif pt_tuple_key[-3::2] == ("parametrizations", "original1"):
        name = pt_tuple_key[-2] + "_v"
    if name is not None:
        renamed_pt_tuple_key = pt_tuple_key[:-3] + (name,)
        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):
    # convert pytorch tensor to numpy
    # numpy currently does not support bfloat16, need to go over float32 in this case to not lose precision
    try:
        import torch  # noqa: F401
    except ImportError:
        logger.error(
            "Loading a PyTorch model in Flax, requires both PyTorch and Flax to be installed. Please see"
            " https://pytorch.org/ and https://flax.readthedocs.io/en/latest/installation.html for installation"
            " instructions."
        )
        raise

    weight_dtypes = {k: v.dtype for k, v in pt_state_dict.items()}
    pt_state_dict = {
        k: v.numpy() if not v.dtype == torch.bfloat16 else v.float().numpy() for k, v in pt_state_dict.items()
    }

    model_prefix = flax_model.base_model_prefix

    # use params dict if the model contains batch norm layers
    if "params" in flax_model.params:
        flax_model_params = flax_model.params["params"]
    else:
        flax_model_params = flax_model.params
    random_flax_state_dict = flatten_dict(flax_model_params)

    # add batch_stats keys,values to dict
    if "batch_stats" in flax_model.params:
        flax_batch_stats = flatten_dict(flax_model.params["batch_stats"])
        random_flax_state_dict.update(flax_batch_stats)

    flax_state_dict = {}

    load_model_with_head_into_base_model = (model_prefix not in flax_model_params) and (
        model_prefix in {k.split(".")[0] for k in pt_state_dict.keys()}
    )
    load_base_model_into_model_with_head = (model_prefix in flax_model_params) and (
        model_prefix not in {k.split(".")[0] for k in pt_state_dict.keys()}
    )

    # Need to change some parameters name to match Flax names
    for pt_key, pt_tensor in pt_state_dict.items():
        pt_tuple_key = tuple(pt_key.split("."))
        is_bfloat_16 = weight_dtypes[pt_key] == torch.bfloat16

        # remove base model prefix if necessary
        has_base_model_prefix = pt_tuple_key[0] == model_prefix
        if load_model_with_head_into_base_model and has_base_model_prefix:
            pt_tuple_key = pt_tuple_key[1:]

        # Correctly rename weight parameters
        flax_key, flax_tensor = rename_key_and_reshape_tensor(
            pt_tuple_key, pt_tensor, random_flax_state_dict, model_prefix
        )

        # add model prefix if necessary
        require_base_model_prefix = (model_prefix,) + flax_key in random_flax_state_dict
        if load_base_model_into_model_with_head and require_base_model_prefix:
            flax_key = (model_prefix,) + flax_key

        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}."
                )

        # add batch stats if the model contains batchnorm layers
        if "batch_stats" in flax_model.params:
            if "mean" in flax_key[-1] or "var" in flax_key[-1]:
                flax_state_dict[("batch_stats",) + flax_key] = jnp.asarray(flax_tensor)
                continue
            # remove num_batches_tracked key
            if "num_batches_tracked" in flax_key[-1]:
                flax_state_dict.pop(flax_key, None)
                continue

            # also add unexpected weight so that warning is thrown
            flax_state_dict[("params",) + flax_key] = (
                jnp.asarray(flax_tensor) if not is_bfloat_16 else jnp.asarray(flax_tensor, dtype=jnp.bfloat16)
            )

        else:
            # also add unexpected weight so that warning is thrown
            flax_state_dict[flax_key] = (
                jnp.asarray(flax_tensor) if not is_bfloat_16 else jnp.asarray(flax_tensor, dtype=jnp.bfloat16)
            )

    return unflatten_dict(flax_state_dict)


############################
# Sharded Pytorch => Flax #
############################


def convert_pytorch_sharded_state_dict_to_flax(shard_filenames, flax_model):
    import torch

    # Load the index
    flax_state_dict = {}
    for shard_file in shard_filenames:
        # load using msgpack utils
        pt_state_dict = torch.load(shard_file)
        pt_state_dict = {k: v.numpy() for k, v in pt_state_dict.items()}

        model_prefix = flax_model.base_model_prefix

        # use params dict if the model contains batch norm layers and then add batch_stats keys,values to dict
        if "batch_stats" in flax_model.params:
            flax_model_params = flax_model.params["params"]

            random_flax_state_dict = flatten_dict(flax_model_params)
            random_flax_state_dict.update(flatten_dict(flax_model.params["batch_stats"]))
        else:
            flax_model_params = flax_model.params
            random_flax_state_dict = flatten_dict(flax_model_params)

        load_model_with_head_into_base_model = (model_prefix not in flax_model_params) and (
            model_prefix in {k.split(".")[0] for k in pt_state_dict.keys()}
        )
        load_base_model_into_model_with_head = (model_prefix in flax_model_params) and (
            model_prefix not in {k.split(".")[0] for k in pt_state_dict.keys()}
        )
        # Need to change some parameters name to match Flax names
        for pt_key, pt_tensor in pt_state_dict.items():
            pt_tuple_key = tuple(pt_key.split("."))

            # remove base model prefix if necessary
            has_base_model_prefix = pt_tuple_key[0] == model_prefix
            if load_model_with_head_into_base_model and has_base_model_prefix:
                pt_tuple_key = pt_tuple_key[1:]

            # Correctly rename weight parameters
            flax_key, flax_tensor = rename_key_and_reshape_tensor(
                pt_tuple_key, pt_tensor, random_flax_state_dict, model_prefix
            )
            # add model prefix if necessary
            require_base_model_prefix = (model_prefix,) + flax_key in random_flax_state_dict
            if load_base_model_into_model_with_head and require_base_model_prefix:
                flax_key = (model_prefix,) + flax_key

            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}."
                    )

            # add batch stats if the model contains batchnorm layers
            if "batch_stats" in flax_model.params:
                if "mean" in flax_key[-1]:
                    flax_state_dict[("batch_stats",) + flax_key] = jnp.asarray(flax_tensor)
                    continue
                if "var" in flax_key[-1]:
                    flax_state_dict[("batch_stats",) + flax_key] = jnp.asarray(flax_tensor)
                    continue
                # remove num_batches_tracked key
                if "num_batches_tracked" in flax_key[-1]:
                    flax_state_dict.pop(flax_key, None)
                    continue

                # also add unexpected weight so that warning is thrown
                flax_state_dict[("params",) + flax_key] = jnp.asarray(flax_tensor)

            else:
                # also add unexpected weight so that warning is thrown
                flax_state_dict[flax_key] = jnp.asarray(flax_tensor)
    return unflatten_dict(flax_state_dict)


#####################
# Flax => PyTorch #
#####################


def load_flax_checkpoint_in_pytorch_model(model, flax_checkpoint_path):
    """Load flax checkpoints in a PyTorch model"""
    flax_checkpoint_path = os.path.abspath(flax_checkpoint_path)
    logger.info(f"Loading Flax weights from {flax_checkpoint_path}")

    # import correct flax class
    flax_cls = getattr(transformers, "Flax" + model.__class__.__name__)

    # load flax weight dict
    with open(flax_checkpoint_path, "rb") as state_f:
        try:
            flax_state_dict = from_bytes(flax_cls, state_f.read())
        except UnpicklingError:
            raise EnvironmentError(f"Unable to convert {flax_checkpoint_path} to Flax deserializable object. ")

    return load_flax_weights_in_pytorch_model(model, flax_state_dict)


def load_flax_weights_in_pytorch_model(pt_model, flax_state):
    """Load flax checkpoints in a PyTorch model"""

    try:
        import torch  # noqa: F401
    except ImportError:
        logger.error(
            "Loading a Flax weights in PyTorch, requires both PyTorch and Flax to be installed. Please see"
            " https://pytorch.org/ and https://flax.readthedocs.io/en/latest/installation.html for installation"
            " instructions."
        )
        raise

    # check if we have bf16 weights
    is_type_bf16 = flatten_dict(jax.tree_util.tree_map(lambda x: x.dtype == jnp.bfloat16, flax_state)).values()
    if any(is_type_bf16):
        # convert all weights to fp32 if the are bf16 since torch.from_numpy can-not handle bf16
        # and bf16 is not fully supported in PT yet.
        logger.warning(
            "Found ``bfloat16`` weights in Flax model. Casting all ``bfloat16`` weights to ``float32`` "
            "before loading those in PyTorch model."
        )
        flax_state = jax.tree_util.tree_map(
            lambda params: params.astype(np.float32) if params.dtype == jnp.bfloat16 else params, flax_state
        )

    flax_state_dict = flatten_dict(flax_state)
    pt_model_dict = pt_model.state_dict()

    load_model_with_head_into_base_model = (pt_model.base_model_prefix in flax_state) and (
        pt_model.base_model_prefix not in {k.split(".")[0] for k in pt_model_dict.keys()}
    )
    load_base_model_into_model_with_head = (pt_model.base_model_prefix not in flax_state) and (
        pt_model.base_model_prefix in {k.split(".")[0] for k in pt_model_dict.keys()}
    )

    # keep track of unexpected & missing keys
    unexpected_keys = []
    missing_keys = set(pt_model_dict.keys())

    for flax_key_tuple, flax_tensor in flax_state_dict.items():
        has_base_model_prefix = flax_key_tuple[0] == pt_model.base_model_prefix
        require_base_model_prefix = ".".join((pt_model.base_model_prefix,) + flax_key_tuple) in pt_model_dict

        # adapt flax_key to prepare for loading from/to base model only
        if load_model_with_head_into_base_model and has_base_model_prefix:
            flax_key_tuple = flax_key_tuple[1:]
        elif load_base_model_into_model_with_head and require_base_model_prefix:
            flax_key_tuple = (pt_model.base_model_prefix,) + flax_key_tuple

        # rename flax weights to PyTorch format
        if flax_key_tuple[-1] == "kernel" and flax_tensor.ndim == 4 and ".".join(flax_key_tuple) not in pt_model_dict:
            # conv layer
            flax_key_tuple = flax_key_tuple[:-1] + ("weight",)
            flax_tensor = jnp.transpose(flax_tensor, (3, 2, 0, 1))
        elif flax_key_tuple[-1] == "kernel" and ".".join(flax_key_tuple) not in pt_model_dict:
            # linear layer
            flax_key_tuple = flax_key_tuple[:-1] + ("weight",)
            flax_tensor = flax_tensor.T
        elif flax_key_tuple[-1] in ["scale", "embedding"]:
            flax_key_tuple = flax_key_tuple[:-1] + ("weight",)

        # adding batch stats from flax batch norm to pt
        elif "mean" in flax_key_tuple[-1]:
            flax_key_tuple = flax_key_tuple[:-1] + ("running_mean",)
        elif "var" in flax_key_tuple[-1]:
            flax_key_tuple = flax_key_tuple[:-1] + ("running_var",)

        if "batch_stats" in flax_state:
            flax_key = ".".join(flax_key_tuple[1:])  # Remove the params/batch_stats header
        else:
            flax_key = ".".join(flax_key_tuple)

        # We also need to look at `pt_model_dict` and see if there are keys requiring further transformation.
        special_pt_names = {}
        # New `weight_norm` from https://github.com/huggingface/transformers/pull/24030
        for key in pt_model_dict:
            key_components = key.split(".")
            name = None
            if key_components[-3::2] == ["parametrizations", "original0"]:
                name = key_components[-2] + "_g"
            elif key_components[-3::2] == ["parametrizations", "original1"]:
                name = key_components[-2] + "_v"
            if name is not None:
                key_components = key_components[:-3] + [name]
                key_to_check = ".".join(key_components)
                special_pt_names[key_to_check] = key

        if flax_key in special_pt_names:
            flax_key = special_pt_names[flax_key]

        if flax_key in pt_model_dict:
            if flax_tensor.shape != pt_model_dict[flax_key].shape:
                raise ValueError(
                    f"Flax checkpoint seems to be incorrect. Weight {flax_key_tuple} was expected "
                    f"to be of shape {pt_model_dict[flax_key].shape}, but is {flax_tensor.shape}."
                )
            else:
                # add weight to pytorch dict
                flax_tensor = np.asarray(flax_tensor) if not isinstance(flax_tensor, np.ndarray) else flax_tensor
                pt_model_dict[flax_key] = torch.from_numpy(flax_tensor)
                # remove from missing keys
                missing_keys.remove(flax_key)
        else:
            # weight is not expected by PyTorch model
            unexpected_keys.append(flax_key)

    pt_model.load_state_dict(pt_model_dict)

    # re-transform missing_keys to list
    missing_keys = list(missing_keys)

    if len(unexpected_keys) > 0:
        logger.warning(
            "Some weights of the Flax model were not used when initializing the PyTorch model"
            f" {pt_model.__class__.__name__}: {unexpected_keys}\n- This IS expected if you are initializing"
            f" {pt_model.__class__.__name__} from a Flax model trained on another task or with another architecture"
            " (e.g. initializing a BertForSequenceClassification model from a FlaxBertForPreTraining model).\n- This"
            f" IS NOT expected if you are initializing {pt_model.__class__.__name__} from a Flax model that you expect"
            " to be exactly identical (e.g. initializing a BertForSequenceClassification model from a"
            " FlaxBertForSequenceClassification model)."
        )
    else:
        logger.warning(f"All Flax model weights were used when initializing {pt_model.__class__.__name__}.\n")
    if len(missing_keys) > 0:
        logger.warning(
            f"Some weights of {pt_model.__class__.__name__} were not initialized from the Flax model and are newly"
            f" 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.warning(
            f"All the weights of {pt_model.__class__.__name__} were initialized from the Flax model.\n"
            "If your task is similar to the task the model of the checkpoint was trained on, "
            f"you can already use {pt_model.__class__.__name__} for predictions without further training."
        )

    return pt_model