# Copyright 2022 The Flax Authors.
#
# 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.
"""Frozen Dictionary."""
import collections
from typing import Any, TypeVar, Mapping, Dict, Tuple
from flax import serialization
import jax
class FrozenKeysView(collections.abc.KeysView):
"""A wrapper for a more useful repr of the keys in a frozen dict."""
def __repr__(self):
return f'frozen_dict_keys({list(self)})'
class FrozenValuesView(collections.abc.ValuesView):
"""A wrapper for a more useful repr of the values in a frozen dict."""
def __repr__(self):
return f'frozen_dict_values({list(self)})'
K = TypeVar('K')
V = TypeVar('V')
def _indent(x, num_spaces):
indent_str = ' ' * num_spaces
lines = x.split('\n')
assert not lines[-1]
# skip the final line because it's empty and should not be indented.
return '\n'.join(indent_str + line for line in lines[:-1]) + '\n'
[docs]@jax.tree_util.register_pytree_node_class
class FrozenDict(Mapping[K, V]):
"""An immutable variant of the Python dict."""
__slots__ = ('_dict', '_hash')
def __init__(self, *args, __unsafe_skip_copy__=False, **kwargs): # pylint: disable=invalid-name
# make sure the dict is as
xs = dict(*args, **kwargs)
if __unsafe_skip_copy__:
self._dict = xs
else:
self._dict = _prepare_freeze(xs)
self._hash = None
def __getitem__(self, key):
v = self._dict[key]
if isinstance(v, dict):
return FrozenDict(v)
return v
def __setitem__(self, key, value):
raise ValueError('FrozenDict is immutable.')
def __contains__(self, key):
return key in self._dict
def __iter__(self):
return iter(self._dict)
def __len__(self):
return len(self._dict)
def __repr__(self):
return self.pretty_repr()
def __reduce__(self):
return FrozenDict, (self.unfreeze(),)
[docs] def pretty_repr(self, num_spaces=4):
"""Returns an indented representation of the nested dictionary."""
def pretty_dict(x):
if not isinstance(x, dict):
return repr(x)
rep = ''
for key, val in x.items():
rep += f'{key}: {pretty_dict(val)},\n'
if rep:
return '{\n' + _indent(rep, num_spaces) + '}'
else:
return '{}'
return f'FrozenDict({pretty_dict(self._dict)})'
def __hash__(self):
if self._hash is None:
h = 0
for key, value in self.items():
h ^= hash((key, value))
self._hash = h
return self._hash
[docs] def copy(self, add_or_replace: Mapping[K, V]) -> 'FrozenDict[K, V]':
"""Create a new FrozenDict with additional or replaced entries."""
return type(self)({**self, **unfreeze(add_or_replace)}) # type: ignore[arg-type]
def keys(self):
return FrozenKeysView(self)
def values(self):
return FrozenValuesView(self)
def items(self):
for key in self._dict:
yield (key, self[key])
[docs] def pop(self, key: K) -> Tuple['FrozenDict[K, V]', V]:
"""Create a new FrozenDict where one entry is removed.
Example::
state, params = variables.pop('params')
Args:
key: the key to remove from the dict
Returns:
A pair with the new FrozenDict and the removed value.
"""
value = self[key]
new_dict = dict(self._dict)
new_dict.pop(key)
new_self = type(self)(new_dict)
return new_self, value
[docs] def unfreeze(self) -> Dict[K, V]:
"""Unfreeze this FrozenDict.
Returns:
An unfrozen version of this FrozenDict instance.
"""
return unfreeze(self)
[docs] def tree_flatten(self) -> Tuple[Tuple[Dict[Any, Any]], Tuple[()]]:
"""Flattens this FrozenDict.
Returns:
A flattened version of this FrozenDict instance.
"""
return (self._dict,), ()
@classmethod
def tree_unflatten(cls, _, data):
# data is already deep copied due to tree map mechanism
# we can skip the deep copy in the constructor
return cls(*data, __unsafe_skip_copy__=True)
def _prepare_freeze(xs: Any) -> Any:
"""Deep copy unfrozen dicts to make the dictionary FrozenDict safe."""
if isinstance(xs, FrozenDict):
# we can safely ref share the internal state of a FrozenDict
# because it is immutable.
return xs._dict # pylint: disable=protected-access
if not isinstance(xs, dict):
# return a leaf as is.
return xs
# recursively copy dictionary to avoid ref sharing
return {key: _prepare_freeze(val) for key, val in xs.items()}
[docs]def freeze(xs: Mapping[Any, Any]) -> FrozenDict[Any, Any]:
"""Freeze a nested dict.
Makes a nested `dict` immutable by transforming it into `FrozenDict`.
Args:
xs: Dictionary to freeze (a regualr Python dict).
Returns:
The frozen dictionary.
"""
return FrozenDict(xs)
[docs]def unfreeze(x: FrozenDict[Any, Any]) -> Dict[Any, Any]:
"""Unfreeze a FrozenDict.
Makes a mutable copy of a `FrozenDict` mutable by transforming
it into (nested) dict.
Args:
x: Frozen dictionary to unfreeze.
Returns:
The unfrozen dictionary (a regular Python dict).
"""
if isinstance(x, FrozenDict):
# deep copy internal state of a FrozenDict
# the dict branch would also work here but
# it is much less performant because jax.tree_util.tree_map
# uses an optimized C implementation.
return jax.tree_util.tree_map(lambda y: y, x._dict) # pylint: disable=protected-access
elif isinstance(x, dict):
ys = {}
for key, value in x.items():
ys[key] = unfreeze(value)
return ys
else:
return x
def _frozen_dict_state_dict(xs):
return {key: serialization.to_state_dict(value) for key, value in xs.items()}
def _restore_frozen_dict(xs, states):
diff = set(map(str, xs.keys())).difference(states.keys())
if diff:
raise ValueError('The target dict keys and state dict keys do not match,'
f' target dict contains keys {diff} which are not present in state dict '
f'at path {serialization.current_path()}')
return FrozenDict(
{key: serialization.from_state_dict(value, states[key], name=key)
for key, value in xs.items()})
serialization.register_serialization_state(
FrozenDict,
_frozen_dict_state_dict,
_restore_frozen_dict)
