tensorflow/python/checkpoint/checkpoint.py
"""Utilities for saving/loading Trackable objects."""
# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
#
# 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 abc
import collections
import copy
import functools
import glob
import inspect
import os
import threading
import time
import weakref
from tensorflow.core.protobuf import trackable_object_graph_pb2
from tensorflow.python.checkpoint import async_checkpoint_helper
from tensorflow.python.checkpoint import checkpoint_context
from tensorflow.python.checkpoint import checkpoint_management
from tensorflow.python.checkpoint import checkpoint_options
from tensorflow.python.checkpoint import functional_saver
from tensorflow.python.checkpoint import graph_view as graph_view_lib
from tensorflow.python.checkpoint import restore as restore_lib
from tensorflow.python.checkpoint import save_util
from tensorflow.python.checkpoint import save_util_v1
from tensorflow.python.checkpoint import util
from tensorflow.python.client import session as session_lib
from tensorflow.python.eager import context
from tensorflow.python.eager import def_function
from tensorflow.python.eager import monitoring
from tensorflow.python.framework import constant_op
from tensorflow.python.framework import dtypes
from tensorflow.python.framework import errors_impl
from tensorflow.python.framework import ops
from tensorflow.python.framework import tensor_shape
from tensorflow.python.framework import tensor_util
from tensorflow.python.lib.io import file_io
from tensorflow.python.ops import array_ops
from tensorflow.python.ops import gen_io_ops as io_ops
from tensorflow.python.ops import init_ops
from tensorflow.python.ops import variable_scope
from tensorflow.python.ops import variable_v1
from tensorflow.python.platform import gfile
from tensorflow.python.platform import tf_logging as logging
from tensorflow.python.saved_model import path_helpers
from tensorflow.python.saved_model.pywrap_saved_model import metrics
from tensorflow.python.trackable import autotrackable
from tensorflow.python.trackable import base
from tensorflow.python.trackable import data_structures
from tensorflow.python.training import py_checkpoint_reader
from tensorflow.python.training import saver as v1_saver_lib
from tensorflow.python.training.saving import saveable_object as saveable_object_lib
from tensorflow.python.training.saving import saveable_object_util
from tensorflow.python.util import compat
from tensorflow.python.util import deprecation
from tensorflow.python.util import object_identity
from tensorflow.python.util import tf_contextlib
from tensorflow.python.util import tf_inspect
from tensorflow.python.util.tf_export import tf_export
# The callable that provide Keras default session that is needed for saving.
_SESSION_PROVIDER = None
# Captures the timestamp of the first Checkpoint instantiation or end of a write
# operation. Can be accessed by multiple Checkpoint instances.
_END_TIME_OF_LAST_WRITE = None
_END_TIME_OF_LAST_WRITE_LOCK = threading.Lock()
# API labels for cell names used in checkpoint metrics.
_CHECKPOINT_V1 = "checkpoint_v1"
_CHECKPOINT_V2 = "checkpoint_v2"
# Async thread used for asynchronous checkpoint.
_ASYNC_CHECKPOINT_THREAD = None
def _get_duration_microseconds(start_time_seconds, end_time_seconds):
if end_time_seconds < start_time_seconds:
# Avoid returning negative value in case of clock skew.
return 0
return round((end_time_seconds - start_time_seconds) * 1000000)
@tf_export("__internal__.tracking.register_session_provider", v1=[])
def register_session_provider(session_provider):
global _SESSION_PROVIDER
# TODO(scottzhu): Change it back to only allow one time setting for session
# provider once we finished the keras repo split.
# if _SESSION_PROVIDER is None:
_SESSION_PROVIDER = session_provider
def get_session():
# Prefer TF's default session since get_session from Keras has side-effects.
session = ops.get_default_session()
if session is None:
global _SESSION_PROVIDER
if _SESSION_PROVIDER is not None:
session = _SESSION_PROVIDER() # pylint: disable=not-callable
return session
def _get_checkpoint_size(prefix):
"""Calculates filesize of checkpoint based on prefix."""
size = 0
# Gather all files beginning with prefix (.index plus sharded data files).
files = glob.glob("{}*".format(prefix))
for file in files:
# Use TensorFlow's C++ FileSystem API.
size += metrics.CalculateFileSize(file)
return size
def _execute_callbacks(callbacks, save_path):
"""Executes a list of callback functions, providing `save_path` if needed."""
for callback in callbacks:
num_params = len(inspect.signature(callback).parameters)
if num_params == 0:
callback()
elif num_params == 1:
callback(save_path)
else:
raise AssertionError(
"Callback functions for checkpoint are required to have 0 or 1"
f"parameters, but this has {num_params} parameters: {callback}"
)
class ObjectGraphProtoPrettyPrinter:
"""Lazily traverses an object graph proto to pretty print names.
If no calls to `node_names` are made this object has no performance
overhead. On the other hand, it will only traverse the object graph once, so
repeated naming is cheap after the first.
"""
__slots__ = ["_object_graph_proto", "_node_name_cache"]
def __init__(self, object_graph_proto):
self._object_graph_proto = object_graph_proto
self._node_name_cache = None
@property
def node_names(self):
"""Lazily creates a mapping from node id to ("path", "to", "root")."""
if self._node_name_cache is not None:
return self._node_name_cache
path_to_root = {}
path_to_root[0] = ("(root)",)
to_visit = collections.deque([0])
while to_visit:
node_id = to_visit.popleft()
obj = self._object_graph_proto.nodes[node_id]
for child in obj.children:
if child.node_id not in path_to_root:
path_to_root[child.node_id] = (
path_to_root[node_id] + (child.local_name,))
to_visit.append(child.node_id)
node_names = {}
for node_id, path_to_root in path_to_root.items():
node_names[node_id] = ".".join(path_to_root)
for node_id, node in enumerate(self._object_graph_proto.nodes):
for slot_reference in node.slot_variables:
node_names[slot_reference.slot_variable_node_id] = (
f"{node_names[node_id]}'s state '{slot_reference.slot_name}' for "
f"{node_names[slot_reference.original_variable_node_id]}")
self._node_name_cache = node_names
return node_names
class _CheckpointRestoreCoordinatorDeleter:
"""Deleter to avoid overriding _CheckpointRestoreCoordinator.__del__()."""
__slots__ = [
"expect_partial", "object_graph_proto", "matched_proto_ids",
"unused_attributes"
]
def __init__(self, expect_partial, object_graph_proto, matched_proto_ids,
unused_attributes):
self.expect_partial = expect_partial
self.object_graph_proto = object_graph_proto
self.matched_proto_ids = matched_proto_ids
self.unused_attributes = unused_attributes
def set_expect_partial(self, expect_partial):
self.expect_partial = expect_partial
def __del__(self):
if self.expect_partial:
return
if logging is None:
# The logging module may have been unloaded when __del__ is called.
log_fn = print
else:
log_fn = logging.warning
unused_nodes_in_checkpoint = []
unrestored_attributes_in_object = []
pretty_printer = ObjectGraphProtoPrettyPrinter(self.object_graph_proto)
for node_id, node in enumerate(self.object_graph_proto.nodes):
if not node.attributes:
continue
if node_id not in self.matched_proto_ids:
unused_nodes_in_checkpoint.append(pretty_printer.node_names[node_id])
for node_id, attribute_name in self.unused_attributes.items():
unrestored_attributes_in_object.append((
pretty_printer.node_names[node_id], attribute_name))
if unused_nodes_in_checkpoint or unrestored_attributes_in_object:
# pylint:disable=line-too-long
log_fn("Detecting that an object or model or tf.train.Checkpoint is being"
" deleted with unrestored values. See the following logs for the "
"specific values in question. To silence these warnings, use "
"`status.expect_partial()`. See "
"https://www.tensorflow.org/api_docs/python/tf/train/Checkpoint#restore"
"for details about the status object returned by the restore "
"function.")
# pylint:enable=line-too-long
for node_path in unused_nodes_in_checkpoint:
log_fn("Value in checkpoint could not be found in the restored object: "
f"{node_path}")
for node_path, attr in unrestored_attributes_in_object:
log_fn("An attribute in the restored object could not be found in the "
f"checkpoint. Object: {node_path}, attribute: {attr}")
class _CheckpointRestoreCoordinator:
"""Holds the status of an object-based checkpoint load."""
def __init__(self, object_graph_proto, save_path, save_path_tensor, reader,
restore_op_cache, graph_view, options, saveables_cache):
"""Specify the checkpoint being loaded.
Args:
object_graph_proto: The TrackableObjectGraph protocol buffer associated
with this checkpoint.
save_path: A string, the path to the checkpoint, as returned by
`tf.train.latest_checkpoint`.
save_path_tensor: A string `Tensor` which contains or will be fed the save
path.
reader: A `CheckpointReader` for `save_path`. If None,
`_CheckpointRestoreCoordinator` will initialize one itself.
restore_op_cache: A dictionary shared between
`_CheckpointRestoreCoordinator`s for the same Python objects, used to
look up restore ops by name to avoid re-creating them across multiple
`restore()` calls.
graph_view: A graph_view_lib.ObjectGraphView object for the restored
objects.
options: A CheckpointOptions object.
saveables_cache: An optional cache storing previously created
SaveableObjects created for each Trackable. Maps Trackables to a
dictionary of attribute names to Trackable.
"""
self.options = options
self.object_graph_proto = object_graph_proto
self.restore_uid = ops.uid()
# Maps from proto ids to lists of attributes which were in the checkpoint
# but not loaded into any object, for error checking.
self.unused_attributes = {}
# Dictionary mapping from an id in the protocol buffer flat array to
# Trackable Python objects. This mapping may be deferred if a
# checkpoint is restored before all dependencies have been tracked. Uses
# weak references so that partial restorations don't create reference cycles
# (as objects with deferred dependencies will generally have references to
# this object).
self.object_by_proto_id = weakref.WeakValueDictionary()
self.matched_proto_ids = set()
# A set of all Python objects we've seen as dependencies, even if we didn't
# use them (for example because of inconsistent references when
# loading). Used to make status assertions fail when loading checkpoints
# that don't quite match.
self.all_python_objects = object_identity.ObjectIdentityWeakSet()
self.save_path_tensor = save_path_tensor
self.save_path_string = save_path
self.dtype_map = reader.get_variable_to_dtype_map()
self.shape_map = reader.get_variable_to_shape_map()
# A NewCheckpointReader for the most recent checkpoint, for streaming Python
# state restoration.
# When graph building, contains a list of ops to run to restore objects from
# this checkpoint.
self.restore_ops = []
self.restore_ops_by_name = restore_op_cache
self.graph_view = graph_view
self.new_restore_ops_callback = None
# A mapping from optimizer proto ids to lists of slot variables to be
# restored when the optimizer is tracked. Only includes slot variables whose
# regular variables have already been created, and only for optimizer
# objects which have not yet been created/tracked.
self.deferred_slot_restorations = {}
# A mapping from variable proto ids to lists of slot variables to be
# restored when the variable is created/tracked. These get shifted over to
# deferred_slot_restorations if the optimizer hasn't been created when that
# happens.
self.slot_restorations = collections.defaultdict(list)
# Controls whether errors are printed in __del__ if some objects did not
# match.
self.expect_partial_attr = False
if not self.options.experimental_skip_slot_variables:
for node_index, node in enumerate(self.object_graph_proto.nodes):
for slot_reference in node.slot_variables:
# `node` refers to an `Optimizer`, since only these have slot
# variables.
self.slot_restorations[
slot_reference.original_variable_node_id
].append(
base._SlotVariableRestoration( # pylint: disable=protected-access
optimizer_id=node_index,
slot_variable_id=slot_reference.slot_variable_node_id,
slot_name=slot_reference.slot_name,
)
)
self._deleter = _CheckpointRestoreCoordinatorDeleter(
self.expect_partial_attr,
self.object_graph_proto,
self.matched_proto_ids,
self.unused_attributes)
self.saveables_cache = saveables_cache
@property
def expect_partial(self):
return self.expect_partial_attr
@expect_partial.setter
def expect_partial(self, expect_partial):
self.expect_partial_attr = expect_partial
self._deleter.set_expect_partial(expect_partial)
def new_restore_ops(self, new_ops):
self.restore_ops.extend(new_ops)
if self.new_restore_ops_callback:
self.new_restore_ops_callback(new_ops) # pylint: disable=not-callable
def restore_saveables(
self,
tensor_saveables,
python_positions,
registered_savers=None,
reader=None,
):
"""Run or build restore operations for SaveableObjects.
Args:
tensor_saveables: `SaveableObject`s which correspond to Tensors.
python_positions: List of CheckpointPositions bound to `PythonState`
objects which must be restored eagerly.
registered_savers: a dict mapping saver names-> object name -> Trackable.
reader: A `CheckpointReader`. If None, a new instance will be created.
Returns:
When graph building, a list of restore operations, either cached or newly
created, to restore `tensor_saveables`.
"""
if reader is None:
reader = py_checkpoint_reader.NewCheckpointReader(self.save_path_string)
restore_ops = []
# Eagerly run restorations for Python state.
for position in python_positions:
key = position.object_proto.attributes[0].checkpoint_key
position.trackable.deserialize(reader.get_tensor(key))
# If we have new SaveableObjects, extract and cache restore ops.
if tensor_saveables or registered_savers:
flat_saveables = saveable_object_util.validate_and_slice_inputs(
tensor_saveables)
new_restore_ops = functional_saver.MultiDeviceSaver.from_saveables(
flat_saveables,
registered_savers).restore(self.save_path_tensor, self.options)
if not context.executing_eagerly():
for name, restore_op in sorted(new_restore_ops.items()):
restore_ops.append(restore_op)
assert name not in self.restore_ops_by_name
self.restore_ops_by_name[name] = restore_op
return restore_ops
class _NameBasedRestoreCoordinator:
"""Keeps the status of a name-based checkpoint restore."""
def __init__(self, save_path, dtype_map=None):
self.save_path = save_path
self.dtype_map = dtype_map
# A map from trackable objects to unused attribute names. We don't have
# proto IDs when doing a name-based restore, so the map keys differ from
# those in _CheckpointRestoreCoordinator.
self.unused_attributes = object_identity.ObjectIdentityWeakKeyDictionary()
self.restore_uid = ops.uid()
def globally_named_object_attributes(self, trackable):
"""Create globally named SaveableObjects from attributes.
If an object's attribute has no global name specified (default construction
for the SaveableObject factory), records the failure in
`self.unused_attributes` (which can then be used to make status assertions
fail; see `NameBasedSaverStatus`).
Args:
trackable: An object to save.
Yields:
SaveableObjects for `trackable`'s attributes.
"""
for (
attribute_name,
saveable_factory,
) in saveable_object_util.saveable_objects_from_trackable(
trackable, tf1_saver=True,
).items():
if callable(saveable_factory):
try:
# This saveable object factory does not have a default name= argument,
# which means there's no way to save/restore it using a name-based
# checkpoint. Ignore the error now and make sure assert_consumed()
# fails.
saveable = saveable_factory()
except TypeError:
self.unused_attributes.setdefault(trackable,
[]).append(attribute_name)
continue
else:
saveable = saveable_factory
names_to_saveables = saveable_object_util.op_list_to_dict(
[saveable], convert_variable_to_tensor=False)
for name, op in names_to_saveables.items():
for saveable_object in saveable_object_util.saveable_objects_for_op(
op=op, name=name):
yield saveable_object
def eager_restore(self, trackable):
"""Runs restore ops for `trackable`'s attributes."""
# When graph building, we don't add any restore ops to the graph until
# run_restore_ops/initialize_or_restore on the status object for name-based
# checkpoints.
assert context.executing_eagerly()
for saveable in self.globally_named_object_attributes(trackable):
restored_tensors = []
tensor_missing = False
for spec in saveable.specs:
if spec.name in self.dtype_map:
with ops.device("cpu:0"):
restored, = io_ops.restore_v2(
prefix=self.save_path,
tensor_names=[spec.name],
shape_and_slices=[""],
dtypes=[self.dtype_map[spec.name]],
name="%s_checkpoint_read" % (spec.name,))
restored_tensors.append(array_ops.identity(restored))
else:
tensor_missing = True
if tensor_missing:
# Record that this variable didn't match so assertions will fail.
self.unused_attributes.setdefault(trackable, []).append(saveable.name)
else:
# Ignores values missing from the checkpoint, as with object-based
# restore. Status assertions can be used to check exact matches,
# although it's unlikely to ever happen for name-based checkpoints.
saveable.restore(
restored_tensors=restored_tensors, restored_shapes=None)
# TODO(allenl): If this ends up in a public API, consider adding LINT.If Change
# or consolidating the implementation with get_variable.
def _default_getter(name,
shape,
dtype,
initializer=None,
partition_info=None,
**kwargs):
"""A pared-down version of get_variable which does not reuse variables."""
dtype = dtypes.as_dtype(dtype)
shape_object = tensor_shape.as_shape(shape)
with ops.init_scope():
if initializer is None:
initializer, initializing_from_value = (
variable_scope._get_default_variable_store()._get_default_initializer( # pylint: disable=protected-access
name=name,
shape=shape_object,
dtype=dtype))
else:
initializing_from_value = not callable(initializer)
# Same logic as get_variable
variable_dtype = dtype.base_dtype
if initializing_from_value:
if shape is not None:
raise ValueError("If initializer is a constant, do not specify shape.")
initial_value = initializer
else:
# Instantiate initializer if provided initializer is a type object.
if isinstance(initializer, type(init_ops.Initializer)):
initializer = initializer(dtype=dtype)
shape_list = None if shape is None else shape_object.as_list()
if "partition_info" in tf_inspect.getargspec(initializer).args:
initial_value = functools.partial(initializer,
shape_list,
dtype=dtype,
partition_info=partition_info)
else:
initial_value = functools.partial(initializer,
shape_list,
dtype=dtype)
return variable_v1.VariableV1(
initial_value=initial_value,
name=name,
dtype=variable_dtype,
use_resource=True,
**kwargs)
def add_variable(trackable,
name,
shape=None,
dtype=dtypes.float32,
initializer=None,
trainable=True):
"""Add a variable to a Trackable with no scope influence."""
return trackable._add_variable_with_custom_getter( # pylint: disable=protected-access
name=name,
shape=shape,
dtype=dtype,
initializer=initializer,
getter=_default_getter,
trainable=trainable)
def object_metadata(save_path):
"""Retrieves information about the objects in a checkpoint.
Example usage:
```python
object_graph = tf.contrib.checkpoint.object_metadata(
tf.train.latest_checkpoint(checkpoint_directory))
ckpt_variable_names = set()
for node in object_graph.nodes:
for attribute in node.attributes:
ckpt_variable_names.add(attribute.full_name)
```
Args:
save_path: The path to the checkpoint, as returned by `save` or
`tf.train.latest_checkpoint`.
Returns:
A parsed `tf.contrib.checkpoint.TrackableObjectGraph` protocol buffer.
Raises:
ValueError: If an object graph was not found in the checkpoint.
"""
reader = py_checkpoint_reader.NewCheckpointReader(save_path)
try:
object_graph_string = reader.get_tensor(base.OBJECT_GRAPH_PROTO_KEY)
except errors_impl.NotFoundError:
raise ValueError(
f"The specified checkpoint \"{save_path}\" does not appear to be "
"object-based (saved with TF2) since it is missing the key "
f"\"{base.OBJECT_GRAPH_PROTO_KEY}\". Likely it was created with the "
"TF1 name-based saver and does not contain an object dependency graph.")
object_graph_proto = (trackable_object_graph_pb2.TrackableObjectGraph())
object_graph_proto.ParseFromString(object_graph_string)
return object_graph_proto
def list_objects(root_trackable):
"""Traverse the object graph and list all accessible objects.
Looks for `Trackable` objects which are dependencies of
`root_trackable`. Includes slot variables only if the variable they are
slotting for and the optimizer are dependencies of `root_trackable`
(i.e. if they would be saved with a checkpoint).
Args:
root_trackable: A `Trackable` object whose dependencies should be flattened.
Returns:
A flat list of objects.
"""
return util.list_objects(graph_view_lib.ObjectGraphView(root_trackable))
def gather_initializers(root_trackable):
"""Traverse the object graph and find initialization ops.
Looks for `Trackable` objects which are dependencies of
`root_trackable` and which have an `initializer` property. Includes
initializers for slot variables only if the variable they are slotting for and
the optimizer are dependencies of `root_trackable` (i.e. if they would be
saved with a checkpoint).
Args:
root_trackable: A `Trackable` object to gather initializers for.
Returns:
A list of initialization ops.
"""
trackable_objects = list_objects(root_trackable)
return [
c.initializer
for c in trackable_objects
if hasattr(c, "initializer") and c.initializer is not None
]
@tf_contextlib.contextmanager
def capture_dependencies(template):
"""Capture variables created within this scope as `Template` dependencies.
Requires that `template.variable_scope` is active.
This scope is intended as a compatibility measure, allowing a trackable
object to add dependencies on variables created in a block of code which is
not aware of object-based saving (and instead uses variable names
heavily). This is how `Template` objects add dependencies on variables and
sub-`Template`s. Where possible, use `tf.compat.v1.make_template` directly.
Args:
template: The `Template` object to register dependencies with.
Yields:
None (when used as a context manager).
"""
name_prefix = template.variable_scope.name
def _trackable_custom_creator(next_creator,
name,
initial_value,
trackable_parent=None,
**kwargs):
"""A variable creation hook which adds Trackable dependencies.
Set for example during a `Template`'s first wrapped function
execution. Ensures that (a) `template` depends on any trackable
objects using their own `capture_dependencies` scope inside this scope which
create variables, and (b) that any variables not in a more deeply nested
scope are added as dependencies directly.
The `trackable_parent` argument is passed between custom creators but
ignored when the variable object itself is created. This argument indicates
(if not `None`) that a more deeply nested scope has already added the
variable as a dependency, and that parent scopes should add a dependency on
that object rather than on the variable directly.
Args:
next_creator: See `variable_scope.variable_creator_scope`; the next
creator in the chain.
name: The (full, scope-influenced) name of the variable. The `name_prefix`
itself is stripped for the purposes of object-based dependency tracking,
but scopes opened within this scope are respected.
initial_value: See `variable_scope.variable_creator_scope`. Taken
explicitly so the argument can be re-named and used with
`Trackable._add_variable_with_custom_getter`.
trackable_parent: If not None, a more deeply nested trackable object and
its name prefix which were passed to `capture_dependencies` to add a
dependency on (rather than depending on the variable directly).
**kwargs: Passed through to the next creator.
Returns:
The output of `next_creator`: the fetched/created variable object.
"""
def _call_next_creator_renaming_initializer(initializer, **inner_kwargs):
inner_kwargs.pop("name") # Ignored; this is the scope-stripped name which
# we don't want to propagate.
return next_creator(initial_value=initializer, name=name, **inner_kwargs)
if name is not None and name.startswith(name_prefix):
scope_stripped_name = name[len(name_prefix) + 1:]
if not trackable_parent:
return template._add_variable_with_custom_getter( # pylint: disable=protected-access
initializer=initial_value,
name=scope_stripped_name,
getter=_call_next_creator_renaming_initializer,
# Disable error checking for Trackable. Exceptions are instead
# raised if necessary when the object-based saver tries to
# save/restore the object.
overwrite=True,
trackable_parent=(template, name_prefix),
**kwargs)
else:
parent_object, parent_name_prefix = trackable_parent
template._track_trackable( # pylint: disable=protected-access
parent_object,
name=parent_name_prefix[len(name_prefix) + 1:],
overwrite=True)
return next_creator(
name=name,
initial_value=initial_value,
trackable_parent=(template, name_prefix),
**kwargs)
with variable_scope.variable_creator_scope(_trackable_custom_creator):
yield
class _LoadStatus:
"""Abstract base for load status callbacks."""
@abc.abstractmethod
def assert_consumed(self):
"""Raises an exception unless a non-trivial restoration has completed."""
pass
@abc.abstractmethod
def assert_existing_objects_matched(self):
"""Raises an exception unless existing Python objects have been matched."""
pass
@abc.abstractmethod
def assert_nontrivial_match(self):
"""Raises an exception if only the root object matched."""
pass
@abc.abstractmethod
def run_restore_ops(self, session=None):
"""Runs restore ops from the checkpoint. Requires a valid checkpoint."""
pass
@abc.abstractmethod
def initialize_or_restore(self, session=None):
"""Runs restore ops from the checkpoint, or initializes variables."""
pass
def expect_partial(self):
"""Silence warnings about incomplete checkpoint restores."""
return self
@tf_export("__internal__.tracking.streaming_restore", v1=[])
def streaming_restore(status, session=None):
"""When graph building, runs restore ops as soon as they come in.
Args:
status: A _LoadStatus objects from an object-based saver's restore().
Streaming restore from name-based checkpoints is not currently supported.
session: A session to run new restore ops in.
"""
if context.executing_eagerly():
# Streaming restore is the default/only behavior when executing eagerly.
return
if session is None:
session = get_session()
if isinstance(status, NameBasedSaverStatus):
raise NotImplementedError(
"Streaming restore not supported from name-based checkpoints when "
"graph building. File a feature request if this limitation bothers "
"you. As a workaround, consider either using tf.train.Checkpoint to "
"load name-based checkpoints or enabling eager execution.")
status.run_restore_ops(session=session)
# pylint: disable=protected-access
status._checkpoint.new_restore_ops_callback = (
lambda ops: session.run(ops, feed_dict=status._feed_dict))
# pylint: enable=protected-access
def _objects_with_attributes(full_list):
"""Filters out objects with no direct variable dependencies for assertions."""
return [
o for o in full_list
if saveable_object_util.saveable_objects_from_trackable(o)
]
class CheckpointLoadStatus(_LoadStatus):
"""Checks the status of checkpoint loading and manages restore ops.
Returned from `Saver.restore`. Since `restore` may defer the loading of values
in the checkpoint which don't yet have corresponding Python objects,
`CheckpointLoadStatus` provides a callback to verify that checkpoint loading
is complete (`assert_consumed`).
When graph building, `restore` does not run restore ops itself since their
creation may be deferred. The `run_restore_ops` method must be called once all
Python objects with values to restore have been created and added to the
dependency graph (this does not necessarily have to be the whole checkpoint;
calling `run_restore_ops` while `assert_consumed` fails is supported and will
partially restore the checkpoint).
See `Saver.restore` for usage examples.
"""
def __init__(self, checkpoint, feed_dict, graph_view, options):
self._checkpoint = checkpoint
self._feed_dict = feed_dict
self._object_graph_view = graph_view
# Keep a reference to the root, since object_graph_view might only have a
# weakref.
self._root = graph_view.root
# CheckpointOptions used for restoring
self._options = options
def assert_consumed(self):
"""Asserts that all objects in the checkpoint have been created/matched.
Returns:
`self` for chaining.
Raises:
AssertionError: If there are any Python objects in the dependency graph
which have not been restored from this checkpoint or a later `restore`,
or if there are any checkpointed values which have not been matched to
Python objects.
"""
pretty_printer = ObjectGraphProtoPrettyPrinter(
self._checkpoint.object_graph_proto)
self.assert_existing_objects_matched()
ignore_node_ids = []
if self._options.experimental_skip_slot_variables:
for node in self._checkpoint.object_graph_proto.nodes:
for sv in node.slot_variables:
ignore_node_ids.append(sv.slot_variable_node_id)
for node_id, node in enumerate(self._checkpoint.object_graph_proto.nodes):
if not node.attributes:
# Only raise exceptions for the nodes with attributes themselves. Either
# they're ultimately not important, or they have a child with an
# attribute.
continue
if node_id in ignore_node_ids:
continue
trackable = self._checkpoint.object_by_proto_id.get(node_id, None)
if trackable is None:
raise AssertionError(
"Unresolved object in checkpoint "
f"{pretty_printer.node_names[node_id]}: {node}")
if (
not self._options.experimental_skip_slot_variables
and self._checkpoint.slot_restorations
):
# Sanity check; this collection should be clear if everything has been
# restored.
raise AssertionError(
f"Unresolved slot restorations: {self._checkpoint.slot_restorations}")
if self._checkpoint.unused_attributes:
unused_attribute_messages = []
for node_id, attribute in self._checkpoint.unused_attributes.items():
obj = self._checkpoint.object_by_proto_id[node_id]
unused_attribute_messages.append(
f"{pretty_printer.node_names[node_id]} ({obj}): {attribute}")
joined_attribute_messages = "\n".join(unused_attribute_messages)
raise AssertionError(
"Unused attributes in these objects (the attributes exist in the "
f"checkpoint but were not restored):\n{joined_attribute_messages}")
return self
def assert_existing_objects_matched(self):
"""Asserts that trackable Python objects have been matched.
Note that this is a weaker assertion than `assert_consumed`. It will only
fail for existing Python objects which are (transitive) dependencies of the
root object and which do not have an entry in the checkpoint.
It will not fail, for example, if a `tf.keras.Layer` object has not yet been
built and so has not created any `tf.Variable` objects.
Returns:
`self` for chaining.
Raises:
AssertionError: If a Python object exists in the transitive dependencies
of the root object but does not have a value in the checkpoint.
"""
for node_id, node in enumerate(self._checkpoint.object_graph_proto.nodes):
trackable = self._checkpoint.object_by_proto_id.get(node_id, None)
if (trackable is not None and
trackable._update_uid < self._checkpoint.restore_uid): # pylint: disable=protected-access
raise AssertionError(
f"Object {node} not assigned a value from checkpoint.")
for trackable_object in util.list_objects(
self._object_graph_view, self._options.experimental_skip_slot_variables
):
# Remove data structures that do not contain any variables from
# restoration checks.
if isinstance(
trackable_object, data_structures.TrackableDataStructure
) and not trackable_object._trackable_children( # pylint: disable=protected-access
save_type=base.SaveType.CHECKPOINT
):
continue
self._checkpoint.all_python_objects.add(trackable_object)
unused_python_objects = (
object_identity.ObjectIdentitySet(
_objects_with_attributes(
self._checkpoint.all_python_objects)) -
object_identity.ObjectIdentitySet(
self._checkpoint.object_by_proto_id.values()))
if unused_python_objects:
num_unused_python_objects = len(list(unused_python_objects))
# Display max number of 10 variables in error message.
num_variables_to_show = min(10, num_unused_python_objects)
raise AssertionError(
f"Found {num_unused_python_objects} Python objects that were "
"not bound to checkpointed values, likely due to changes in the "
f"Python program. Showing {num_variables_to_show} of "
f"{num_unused_python_objects} unmatched objects: "
f"{list(unused_python_objects)[:num_variables_to_show]}")
return self
def assert_nontrivial_match(self):
"""Raises an exception if only the root object matched."""
for trackable_object in util.list_objects(
self._object_graph_view, self._options.experimental_skip_slot_variables
):
self._checkpoint.all_python_objects.add(trackable_object)
if len(self._checkpoint.object_by_proto_id) <= 1:
unused_python_objects = object_identity.ObjectIdentitySet(
_objects_with_attributes(self._checkpoint.all_python_objects)
) - object_identity.ObjectIdentitySet(
self._checkpoint.object_by_proto_id.values()
)
if unused_python_objects:
raise AssertionError(
"Nothing except the root object matched a checkpointed value. "
"Typically this means that the checkpoint does not match the "
"Python program. The following objects have no matching "
f"checkpointed value: {list(unused_python_objects)}"
)
else:
raise AssertionError(
"Nothing to load. No dependencies have been added to "
f"{self._object_graph_view.root} yet."
)
return self
def run_restore_ops(self, session=None):
"""Run operations to restore objects in the dependency graph."""
if context.executing_eagerly():
return # Run eagerly
if session is None:
session = get_session()
session.run(self._checkpoint.restore_ops, feed_dict=self._feed_dict)
def initialize_or_restore(self, session=None):
"""Run operations to initialize or restore objects in the dependency graph.
Any objects in the dependency graph which have initializers but are not in
the checkpoint will have those initializers run, unless those variables are
being restored by a later call to `tf.train.Checkpoint.restore()`.
This method has a sibling in `InitializationOnlyStatus` which instead
initializes variables. That type is returned if no checkpoint is specified
in `Saver.restore`.
Args:
session: The session to run init/restore ops in. If `None`, uses the
default session.
"""
if context.executing_eagerly():
return # Initialization and restoration ops are run eagerly
if session is None:
session = get_session()
all_objects = util.list_objects(self._object_graph_view)
already_initialized_objects = object_identity.ObjectIdentitySet(
self._checkpoint.object_by_proto_id.values())
initializers_for_non_restored_variables = [
c.initializer for c in all_objects
if hasattr(c, "initializer")
and c not in already_initialized_objects
and (getattr(c, "_update_uid", self._checkpoint.restore_uid - 1)
< self._checkpoint.restore_uid)
]
self.run_restore_ops(session=session)
session.run(initializers_for_non_restored_variables)
def expect_partial(self):
"""Silence warnings about incomplete checkpoint restores."""
self._checkpoint.expect_partial = True
return self
class InitializationOnlyStatus(_LoadStatus):
"""Returned from `Saver.restore` when no checkpoint has been specified.
Objects of this type have the same `assert_consumed` method as
`CheckpointLoadStatus`, but it always fails. However,
`initialize_or_restore` works on objects of both types, and will
initialize variables in `InitializationOnlyStatus` objects or restore them
otherwise.
"""
def __init__(self, object_graph_view, restore_uid):
self._restore_uid = restore_uid
self._object_graph_view = object_graph_view
# Keep a reference to the root, since graph_view might only have a weakref.
self._root = object_graph_view.root
def assert_consumed(self):
"""Assertion for consistency with `CheckpointLoadStatus`. Always fails."""
raise AssertionError(
"No checkpoint specified (save_path=None); nothing is being restored.")
def assert_existing_objects_matched(self):
"""Assertion for consistency with `CheckpointLoadStatus`. Always fails."""
raise AssertionError(
"No checkpoint specified (save_path=None); nothing is being restored.")
def assert_nontrivial_match(self):
"""Assertion for consistency with `CheckpointLoadStatus`. Always fails."""
raise AssertionError(
"No checkpoint specified (save_path=None); nothing is being restored.")
def run_restore_ops(self, session=None):
"""For consistency with `CheckpointLoadStatus`.
Use `initialize_or_restore` for initializing if no checkpoint was passed
to `Saver.restore` and restoring otherwise.
Args:
session: Not used.
"""
raise AssertionError(
"No checkpoint specified, so no restore ops are available "
"(save_path=None to Saver.restore).")
def initialize_or_restore(self, session=None):
"""Runs initialization ops for variables.
Objects which would be saved by `Saver.save` will be initialized, unless
those variables are being restored by a later call to
`tf.train.Checkpoint.restore()`.
This method does nothing when executing eagerly (initializers get run
eagerly).
Args:
session: The session to run initialization ops in. If `None`, uses the
default session.
"""
if context.executing_eagerly():
return # run eagerly
if session is None:
session = get_session()
trackable_objects = util.list_objects(self._object_graph_view)
initializers = [
c.initializer for c in trackable_objects
if hasattr(c, "initializer") and c.initializer is not None
and (getattr(c, "_update_uid", self._restore_uid - 1)
< self._restore_uid)
]
session.run(initializers)
_DEPRECATED_RESTORE_INSTRUCTIONS = (
"Restoring a name-based tf.train.Saver checkpoint using the object-based "
"restore API. This mode uses global names to match variables, and so is "
"somewhat fragile. It also adds new restore ops to the graph each time it "
"is called when graph building. Prefer re-encoding training checkpoints in "
"the object-based format: run save() on the object-based saver (the same "
"one this message is coming from) and use that checkpoint in the future.")
class NameBasedSaverStatus(_LoadStatus):
"""Status for loading a name-based training checkpoint."""
# Ideally this deprecation decorator would be on the class, but that
# interferes with isinstance checks.
@deprecation.deprecated(
date=None, instructions=_DEPRECATED_RESTORE_INSTRUCTIONS)
def __init__(self, checkpoint, object_graph_view):
self._checkpoint = checkpoint
self._object_graph_view = object_graph_view
self._optionally_restored = []
# Keep a reference to the root, since graph_view might only have a weakref.
self._root = object_graph_view.root
def add_to_optionally_restored(self, var):
"""Add a variable to the list of optionally restored variables.
There are situations where certain variables should be ignored in assertions
such as assert_existing_objects_matched(). One example is that of a
checkpoint saved with train.Saver(), and restored with train.Checkpoint():
it is possible for the train.Saver() checkpoint to be missing the internal
`save_counter` variable, which we want to ignore on restore.
Args:
var: The variable to treat as optionally restored.
"""
self._optionally_restored.append(var)
def assert_consumed(self):
"""Raises an exception if any variables are unmatched."""
unused_attributes = list(self._checkpoint.unused_attributes.items())
unused_attributes = [
a for a in unused_attributes
if all(a[0] is not x for x in self._optionally_restored)
]
if unused_attributes:
unused_attribute_string = "".join(
f"\n {obj}: {attributes}" for obj, attributes in unused_attributes)
raise AssertionError(
"Some objects had attributes which were not restored: "
f"{unused_attribute_string}")
for trackable in util.list_objects(self._object_graph_view):
# pylint: disable=protected-access
trackable._maybe_initialize_trackable()
if trackable._update_uid < self._checkpoint.restore_uid:
raise AssertionError(f"Object not restored: {trackable}")
# pylint: enable=protected-access
return self
def assert_existing_objects_matched(self):
"""Raises an exception if currently created objects are unmatched."""
# For name-based checkpoints there's no object information in the
# checkpoint, so there's no distinction between
# assert_existing_objects_matched and assert_consumed (and both are less
# useful since we don't touch Python objects or Python state).
return self.assert_consumed()
def assert_nontrivial_match(self):
"""Raises an exception if currently created objects are unmatched."""
# For name-based checkpoints there's no object information in the
# checkpoint, so there's no distinction between
# assert_nontrivial_match and assert_consumed (and both are less
# useful since we don't touch Python objects or Python state).
return self.assert_consumed()
def _gather_saveable_objects(self):
"""Walk the object graph, using global names for SaveableObjects."""
objects = util.list_objects(self._object_graph_view)
saveable_objects = []
for trackable in objects:
# pylint: disable=protected-access
trackable._maybe_initialize_trackable()
if trackable._update_uid < self._checkpoint.restore_uid:
trackable._update_uid = self._checkpoint.restore_uid
else:
continue
# pylint: enable=protected-access
saveable_objects.extend(
self._checkpoint.globally_named_object_attributes(trackable))
return saveable_objects
def run_restore_ops(self, session=None):
"""Load the name-based checkpoint using a new `tf.compat.v1.train.Saver`."""
if context.executing_eagerly():
return # Nothing to do, variables are restored on creation.
if session is None:
session = get_session()
with ops.device("/cpu:0"):
saveables = self._gather_saveable_objects()
v1_saver_lib.Saver(saveables).restore(
sess=session, save_path=self._checkpoint.save_path)
def initialize_or_restore(self, session=None):
"""Alias for `run_restore_ops`."""
self.run_restore_ops(session=session)
class _SessionWithFeedDictAdditions(session_lib.SessionInterface):
"""Pretends to be a session, inserts extra feeds on run()."""
def __init__(self, session, feed_additions):
self._wrapped_session = session
self._feed_additions = feed_additions
def run(self, fetches, feed_dict=None, **kwargs):
if feed_dict is None:
feed_dict = {}
else:
feed_dict = feed_dict.copy()
feed_dict.update(self._feed_additions)
return self._wrapped_session.run(
fetches=fetches, feed_dict=feed_dict, **kwargs)
class TrackableSaver:
"""Saves and restores a `Trackable` object and its dependencies.
See `Trackable` for details of dependency management. `Saver` wraps
`tf.compat.v1.train.Saver` for saving, including extra information about the
graph of
dependencies between Python objects. When restoring, it uses this information
about the save-time dependency graph to more robustly match objects with their
checkpointed values. When executing eagerly, it supports restoring variables
on object creation (see `Saver.restore`).
Values in a checkpoint are mapped to `Trackable` Python objects
(`Variable`s, `Optimizer`s, `Layer`s) based on the names provided when the
checkpoint was written. To avoid breaking existing checkpoints when modifying
a class, dependency names (the names of attributes to which `Trackable`
objects are assigned) may not change. These names are local to objects, in
contrast to the `Variable.name`-based save/restore from
`tf.compat.v1.train.Saver`, and
so allow additional program transformations.
"""
def __init__(self, graph_view):
"""Configure saving.
Args:
graph_view: An `ObjectGraphView` object containing a description of the
object graph to save.
"""
self._graph_view = graph_view
# The following attributes are used when graph building.
# self._cache: A more generic cache used to cache the serialized tensors and
# TrackableObjectGraph proto attributes.
# self._saveables_cache: A dictionary mapping `Trackable` objects ->
# attribute names -> SaveableObjects, used to avoid re-creating
# SaveableObjects when graph building.
if context.executing_eagerly():
self._cache = None
self._saveables_cache = None
else:
self._cache = object_identity.ObjectIdentityWeakKeyDictionary()
self._saveables_cache = object_identity.ObjectIdentityWeakKeyDictionary()
# The file prefix placeholder is created lazily when graph building (and not
# at all when executing eagerly) to avoid creating ops in the constructor
# (when they may never be necessary).
self._file_prefix_placeholder = None
# Op caching for save
self._object_graph_feed_tensor = None
self._last_save_object_graph = None
self._file_prefix_feed_tensor = None
self._cached_save_operation = None
# Op caching for restore, shared between _CheckpointRestoreCoordinators
self._restore_op_cache = {}
# Object map used for checkpoint. This attribute is to be overridden by a
# Checkpoint subclass, e.g., AsyncCheckpoint, to replace the trackable
# objects for checkpoint saving.
self._object_map = None
def _gather_serialized_tensors(self, object_graph_tensor=None):
"""Gathers tensors to save to ckpt and includes the object graph proto."""
serialized_tensors, feed_additions, registered_savers, graph_proto = (
save_util.serialize_graph_view(self._graph_view,
self._object_map,
cache=self._cache))
if self._saveables_cache is not None:
# Store saveables cache for restoration purposes.
self._saveables_cache = (
saveable_object_util.serialized_tensors_to_saveable_cache(
serialized_tensors))
if object_graph_tensor is None:
with ops.device("/cpu:0"):
object_graph_tensor = constant_op.constant(
graph_proto.SerializeToString(), dtype=dtypes.string)
else:
feed_additions.update(
{object_graph_tensor: graph_proto.SerializeToString()})
assert base.OBJECT_GRAPH_PROTO_KEY not in serialized_tensors.get(None, {})
serialized_tensors.setdefault(None, {})[base.OBJECT_GRAPH_PROTO_KEY] = (
object_graph_tensor)
return serialized_tensors, feed_additions, registered_savers, graph_proto
def _save_cached_when_graph_building(self, file_prefix, object_graph_tensor,
options):
"""Create or retrieve save ops.
Args:
file_prefix: The prefix for saved checkpoint files.
object_graph_tensor: A `Tensor` to which the current object graph will be
fed.
options: `CheckpointOptions` object.
Returns:
A two-element tuple with a filename tensor and a feed_dict of tensors to
feed when running it (if graph building). The feed dict contains the
current object graph and any Python state to be saved in the
checkpoint. When executing eagerly only the first argument is meaningful.
"""
serialized_tensors, feed_additions, registered_savers, graph_proto = (
self._gather_serialized_tensors(object_graph_tensor))
if (self._last_save_object_graph != graph_proto
# When executing eagerly, we need to re-create SaveableObjects each
# time save() is called so they pick up new Tensors passed to their
# constructors. That means the Saver needs to be copied with a new
# var_list.
or context.executing_eagerly() or ops.inside_function()):
saver = functional_saver.MultiDeviceSaver(serialized_tensors,
registered_savers)
save_op = saver.save(file_prefix, options=options)
with ops.device("/cpu:0"):
with ops.control_dependencies([save_op]):
self._cached_save_operation = array_ops.identity(file_prefix)
self._last_save_object_graph = graph_proto
return self._cached_save_operation, feed_additions
def save(self,
file_prefix,
checkpoint_number=None,
session=None,
options=None):
"""Save a training checkpoint.
The saved checkpoint includes variables created by this object and any
Trackable objects it depends on at the time `Saver.save()` is called.
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix). Names are generated based on this
prefix and `checkpoint_number`, if provided.
checkpoint_number: An integer variable or Tensor, used to number
checkpoints. Typically this value is saved along with other variables in
training checkpoints, which will happen automatically if it was created
by `root_trackable` or one of its dependencies (via
`Trackable._add_variable`).
session: The session to evaluate variables in. Ignored when executing
eagerly. If not provided when graph building, the default session is
used.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint.
Raises:
RuntimeError: if called in V1 Graph mode without a default session.
"""
options = options or checkpoint_options.CheckpointOptions()
feed_dict = {}
use_session = (not context.executing_eagerly() and
not ops.inside_function())
if checkpoint_number:
file_prefix = "%s-%d" % (file_prefix, checkpoint_number)
if use_session:
if self._object_graph_feed_tensor is None:
with ops.device("/cpu:0"):
self._object_graph_feed_tensor = constant_op.constant(
"", dtype=dtypes.string)
self._file_prefix_feed_tensor = constant_op.constant(
"", dtype=dtypes.string)
object_graph_tensor = self._object_graph_feed_tensor
file_prefix_tensor = self._file_prefix_feed_tensor
feed_dict[file_prefix_tensor] = file_prefix
else:
with ops.device("/cpu:0"):
file_prefix_tensor = ops.convert_to_tensor(
file_prefix, dtype=dtypes.string)
object_graph_tensor = None
if not tensor_util.is_tensor(file_prefix):
file_io.recursive_create_dir(os.path.dirname(file_prefix))
save_path, new_feed_additions = self._save_cached_when_graph_building(
file_prefix_tensor, object_graph_tensor, options)
if new_feed_additions:
feed_dict.update(new_feed_additions)
if not use_session:
session = None
elif session is None:
session = get_session()
if session:
return session.run(save_path, feed_dict=feed_dict)
elif use_session:
raise RuntimeError(f"Unable to save checkpoint to \"{file_prefix}\" "
"in graph mode without a default session. Please use "
"`with tf.Session():` to create a session.")
else:
return save_path
def restore(self, save_path, options=None):
"""Restore a training checkpoint.
Restores `root_trackable` and any objects that it tracks
(transitive). Either assigns values immediately if variables to restore have
been created already, or defers restoration until the variables are
created. Dependencies added to the `root_trackable` passed to the
constructor after this call will be matched if they have a corresponding
object in the checkpoint.
When building a graph, restorations are added to the graph but not run.
```python
saver = Saver(root)
saver.restore(path)
```
To ensure that loading is complete and no more deferred restorations will
take place, you can use the `assert_consumed()` method of the status object
returned by the `restore` call.
The assert will raise an exception unless every object was matched and all
checkpointed values have a matching variable object.
```python
saver = Saver(root)
saver.restore(path).assert_consumed()
```
When graph building, `assert_consumed()` indicates that all of the restore
ops which will be created for this checkpoint have been created. They can be
run via the `run_restore_ops()` function of the status object:
```python
saver.restore(path).assert_consumed().run_restore_ops()
```
If the checkpoint has not been consumed completely, then the list of restore
ops will grow as more objects are added to the dependency graph.
Name-based `tf.compat.v1.train.Saver` checkpoints can be loaded using this
method. There is no deferred loading, and names are used to match
variables. No restore ops are created/run until `run_restore_ops()` or
`initialize_or_restore()` are called on the returned status object, even
when executing eagerly. Re-encode name-based checkpoints using this
object-based `Saver.save` as soon as possible.
Args:
save_path: The path to the checkpoint, as returned by `save` or
`tf.train.latest_checkpoint`. If None (as when there is no latest
checkpoint for `tf.train.latest_checkpoint` to return), returns an
object which may run initializers for objects in the dependency graph.
If the checkpoint was written by the name-based
`tf.compat.v1.train.Saver`, names are used to match variables.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
A load status object, which can be used to make assertions about the
status of checkpoint restoration and run initialization/restore ops
(of type `CheckpointLoadStatus`, or `InitializationOnlyStatus` if
`save_path` is `None`).
If `save_path` points to a name-based checkpoint, a `NameBasedSaverStatus`
object is returned which runs restore ops from a name-based saver.
Raises:
RuntimeError: When a checkpoint file saved by async checkpoint is not
available upon restore().
"""
options = options or checkpoint_options.CheckpointOptions()
if save_path is None:
return InitializationOnlyStatus(self._graph_view, ops.uid())
# Wait until the ongoing checkpoint to finish.
# TODO(chienchunh): Allow to load the file while other checkpoint events
# are still ongiing. Need to add timeout mechanism along
# with conditional variables to notify when the checkpoint
# file is ready.
global _ASYNC_CHECKPOINT_THREAD
if _ASYNC_CHECKPOINT_THREAD is not None:
_ASYNC_CHECKPOINT_THREAD.join()
reader = py_checkpoint_reader.NewCheckpointReader(save_path)
graph_building = not context.executing_eagerly()
if graph_building:
dtype_map = None
else:
dtype_map = reader.get_variable_to_dtype_map()
try:
object_graph_string = reader.get_tensor(base.OBJECT_GRAPH_PROTO_KEY)
except errors_impl.NotFoundError:
# The object graph proto does not exist in this checkpoint. Try the
# name-based compatibility mode.
restore_coordinator = _NameBasedRestoreCoordinator(
save_path=save_path,
dtype_map=dtype_map)
if not graph_building:
for existing_trackable in util.list_objects(self._graph_view):
# pylint: disable=protected-access
existing_trackable._maybe_initialize_trackable()
existing_trackable._name_based_restores.add(restore_coordinator)
existing_trackable._name_based_attribute_restore(restore_coordinator)
# pylint: enable=protected-access
return NameBasedSaverStatus(
restore_coordinator,
object_graph_view=self._graph_view)
if graph_building:
if self._file_prefix_placeholder is None:
with ops.device("/cpu:0"):
self._file_prefix_placeholder = constant_op.constant("model")
file_prefix_tensor = self._file_prefix_placeholder
file_prefix_feed_dict = {self._file_prefix_placeholder: save_path}
else:
with ops.device("/cpu:0"):
file_prefix_tensor = constant_op.constant(save_path)
file_prefix_feed_dict = None
object_graph_proto = (trackable_object_graph_pb2.TrackableObjectGraph())
object_graph_proto.ParseFromString(object_graph_string)
checkpoint = _CheckpointRestoreCoordinator(
object_graph_proto=object_graph_proto,
save_path=save_path,
save_path_tensor=file_prefix_tensor,
reader=reader,
restore_op_cache=self._restore_op_cache,
graph_view=self._graph_view,
options=options,
saveables_cache=self._saveables_cache)
restore_lib.CheckpointPosition(
checkpoint=checkpoint, proto_id=0).restore(self._graph_view.root,
reader)
# Attached dependencies are not attached to the root, so should be restored
# separately.
if self._graph_view.attached_dependencies:
for ref in self._graph_view.attached_dependencies:
if ref.name == "root":
# Root dependency is automatically added to attached dependencies --
# this can be ignored since it maps back to the root object.
continue
proto_id = None
# Find proto ID of attached dependency (if it is in the proto).
for proto_ref in object_graph_proto.nodes[0].children:
if proto_ref.local_name == ref.name:
proto_id = proto_ref.node_id
break
if proto_id in checkpoint.object_by_proto_id:
# Object has already been restored. This can happen when there's an
# indirect connection from the attached object to the root.
continue
if proto_id is None:
# Could not find attached dependency in proto.
continue
restore_lib.CheckpointPosition(
checkpoint=checkpoint,
proto_id=proto_id).restore(ref.ref, reader)
load_status = CheckpointLoadStatus(
checkpoint,
graph_view=self._graph_view,
feed_dict=file_prefix_feed_dict,
options=options)
return load_status
def frozen_saver(root_trackable):
"""Creates a static `tf.compat.v1.train.Saver` from a trackable object.
The returned `Saver` saves object-based checkpoints, but these checkpoints
will no longer reflect structural changes to the object graph, only changes to
the values of `Variable`s added as dependencies of the root object before
`freeze` was called.
`restore` works on the returned `Saver`, but requires that the object graph of
the checkpoint being loaded exactly matches the object graph when `freeze` was
called. This is in contrast the object-based restore performed by
`tf.train.Checkpoint` which attempts a fuzzy matching between a checkpoint's
object graph and the current Python object graph.
Args:
root_trackable: A trackable object to save.
Returns:
A saver which saves object-based checkpoints for the object graph frozen at
the time `frozen_saver` was called.
"""
named_saveable_objects, registered_savers = (
save_util_v1.frozen_saveables_and_savers(
graph_view_lib.ObjectGraphView(root_trackable)))
return functional_saver.MultiDeviceSaver.from_saveables(
named_saveable_objects, registered_savers)
def _assert_trackable(obj, name):
if not isinstance(
obj, (base.Trackable, def_function.Function)):
raise ValueError(
f"`Checkpoint` was expecting {name} to be a trackable object (an "
f"object derived from `Trackable`), got {obj}. If you believe this "
"object should be trackable (i.e. it is part of the "
"TensorFlow Python API and manages state), please open an issue.")
def _update_checkpoint_state_internal(file_path):
"""Update internal checkpoint state."""
checkpoint_management.update_checkpoint_state_internal(
save_dir=os.path.dirname(file_path),
model_checkpoint_path=file_path,
all_model_checkpoint_paths=[file_path],
save_relative_paths=True)
def _convert_file_name_tensor_to_string(tensor):
"""Convert file name tensor to string."""
output = tensor
if tensor_util.is_tf_type(output):
# Convert to numpy if not `tf.function` building.
if context.executing_eagerly():
output = compat.as_str(output.numpy())
else:
# Graph + Session, so we already session.ran it.
output = compat.as_str(output)
return output
def _copy_single_tensor(tensor):
"""Copies a single Tensor / SaveSpec onto the CPU device."""
device = tensor.device
if isinstance(tensor, saveable_object_lib.SaveSpec):
# Pin the device according to the tensor's device location to
# avoid unnecessary data copies when reading the variables. This is
# aligned with the behavior in MultiDeviceSaver.save().
with ops.device(device):
tensor = tensor.tensor
if tensor is not None:
with ops.device(saveable_object_util.set_cpu0(device)):
tensor = array_ops.identity(tensor) # pylint: disable=protected-access
return tensor
# Mentions graph building / Sessions. The v2 version is below.
@tf_export(v1=["train.Checkpoint"])
class CheckpointV1(autotrackable.AutoTrackable):
"""Groups trackable objects, saving and restoring them.
`Checkpoint`'s constructor accepts keyword arguments whose values are types
that contain trackable state, such as `tf.compat.v1.train.Optimizer`
implementations, `tf.Variable`, `tf.keras.Layer` implementations, or
`tf.keras.Model` implementations. It saves these values with a checkpoint, and
maintains a `save_counter` for numbering checkpoints.
Example usage when graph building:
```python
import tensorflow as tf
import os
checkpoint_directory = "/tmp/training_checkpoints"
checkpoint_prefix = os.path.join(checkpoint_directory, "ckpt")
checkpoint = tf.train.Checkpoint(optimizer=optimizer, model=model)
status = checkpoint.restore(tf.train.latest_checkpoint(checkpoint_directory))
train_op = optimizer.minimize( ... )
status.assert_consumed() # Optional sanity checks.
with tf.compat.v1.Session() as session:
# Use the Session to restore variables, or initialize them if
# tf.train.latest_checkpoint returned None.
status.initialize_or_restore(session)
for _ in range(num_training_steps):
session.run(train_op)
checkpoint.save(file_prefix=checkpoint_prefix)
```
Example usage with eager execution enabled:
```python
import tensorflow as tf
import os
tf.compat.v1.enable_eager_execution()
checkpoint_directory = "/tmp/training_checkpoints"
checkpoint_prefix = os.path.join(checkpoint_directory, "ckpt")
checkpoint = tf.train.Checkpoint(optimizer=optimizer, model=model)
status = checkpoint.restore(tf.train.latest_checkpoint(checkpoint_directory))
for _ in range(num_training_steps):
optimizer.minimize( ... ) # Variables will be restored on creation.
status.assert_consumed() # Optional sanity checks.
checkpoint.save(file_prefix=checkpoint_prefix)
```
`Checkpoint.save` and `Checkpoint.restore` write and read object-based
checkpoints, in contrast to `tf.compat.v1.train.Saver` which writes and reads
`variable.name` based checkpoints. Object-based checkpointing saves a graph of
dependencies between Python objects (`Layer`s, `Optimizer`s, `Variable`s,
etc.) with named edges, and this graph is used to match variables when
restoring a checkpoint. It can be more robust to changes in the Python
program, and helps to support restore-on-create for variables when executing
eagerly. Prefer `tf.train.Checkpoint` over `tf.compat.v1.train.Saver` for new
code.
`Checkpoint` objects have dependencies on the objects passed as keyword
arguments to their constructors, and each dependency is given a name that is
identical to the name of the keyword argument for which it was created.
TensorFlow classes like `Layer`s and `Optimizer`s will automatically add
dependencies on their variables (e.g. "kernel" and "bias" for
`tf.keras.layers.Dense`). Inheriting from `tf.keras.Model` makes managing
dependencies easy in user-defined classes, since `Model` hooks into attribute
assignment. For example:
```python
class Regress(tf.keras.Model):
def __init__(self):
super().__init__()
self.input_transform = tf.keras.layers.Dense(10)
# ...
def call(self, inputs):
x = self.input_transform(inputs)
# ...
```
This `Model` has a dependency named "input_transform" on its `Dense` layer,
which in turn depends on its variables. As a result, saving an instance of
`Regress` using `tf.train.Checkpoint` will also save all the variables created
by the `Dense` layer.
When variables are assigned to multiple workers, each worker writes its own
section of the checkpoint. These sections are then merged/re-indexed to behave
as a single checkpoint. This avoids copying all variables to one worker, but
does require that all workers see a common filesystem.
While `tf.keras.Model.save_weights` and `tf.train.Checkpoint.save` save in the
same format, note that the root of the resulting checkpoint is the object the
save method is attached to. This means saving a `tf.keras.Model` using
`save_weights` and loading into a `tf.train.Checkpoint` with a `Model`
attached (or vice versa) will not match the `Model`'s variables. See the
[guide to training
checkpoints](https://www.tensorflow.org/guide/checkpoint) for
details. Prefer `tf.train.Checkpoint` over `tf.keras.Model.save_weights` for
training checkpoints.
Attributes:
save_counter: Incremented when `save()` is called. Used to number
checkpoints.
"""
def __init__(self, **kwargs):
"""Group objects into a training checkpoint.
Args:
**kwargs: Keyword arguments are set as attributes of this object, and are
saved with the checkpoint. Values must be trackable objects.
Raises:
ValueError: If objects in `kwargs` are not trackable.
"""
super().__init__()
global _END_TIME_OF_LAST_WRITE
with _END_TIME_OF_LAST_WRITE_LOCK:
if _END_TIME_OF_LAST_WRITE is None:
_END_TIME_OF_LAST_WRITE = time.time()
for k, v in sorted(kwargs.items(), key=lambda item: item[0]):
setattr(self, k, v)
if not isinstance(
getattr(self, k), (base.Trackable, def_function.Function)):
raise ValueError(
"`Checkpoint` was expecting a trackable object (an object "
f"derived from `Trackable`), got {v}. If you believe this "
"object should be trackable (i.e. it is part of the "
"TensorFlow Python API and manages state), please open an issue.")
self._save_counter = None # Created lazily for restore-on-create.
self._save_assign_op = None
self._saver = TrackableSaver(graph_view_lib.ObjectGraphView(self))
def _maybe_create_save_counter(self):
"""Create a save counter if it does not yet exist."""
if self._save_counter is None:
# Initialized to 0 and incremented before saving.
with ops.device("/cpu:0"):
# add_variable creates a dependency named "save_counter"; NoDependency
# prevents creating a second dependency named "_save_counter".
self._save_counter = data_structures.NoDependency(
add_variable(
self,
name="save_counter",
initializer=0,
dtype=dtypes.int64,
trainable=False))
def write(self, file_prefix, session=None, options=None):
"""Writes a training checkpoint.
The checkpoint includes variables created by this object and any
trackable objects it depends on at the time `Checkpoint.write()` is
called.
`write` does not number checkpoints, increment `save_counter`, or update the
metadata used by `tf.train.latest_checkpoint`. It is primarily intended for
use by higher level checkpoint management utilities. `save` provides a very
basic implementation of these features.
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix).
session: The session to evaluate variables in. Ignored when executing
eagerly. If not provided when graph building, the default session is
used.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint (i.e. `file_prefix`).
"""
return self._write(file_prefix, session, options=options)
def _write(self, file_prefix, session=None, options=None):
"""Writes a training checkpoint.
The checkpoint includes variables created by this object and any
trackable objects it depends on at the time `Checkpoint.write()` is
called.
`write` does not number checkpoints, increment `save_counter`, or update the
metadata used by `tf.train.latest_checkpoint`. It is primarily intended for
use by higher level checkpoint management utilities. `save` provides a very
basic implementation of these features.
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix).
session: The session to evaluate variables in. Ignored when executing
eagerly. If not provided when graph building, the default session is
used.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint (i.e. `file_prefix`).
"""
start_time = time.time()
output = self._saver.save(file_prefix=file_prefix, session=session,
options=options)
end_time = time.time()
metrics.AddCheckpointWriteDuration(
api_label=_CHECKPOINT_V1,
microseconds=_get_duration_microseconds(start_time, end_time))
global _END_TIME_OF_LAST_WRITE
with _END_TIME_OF_LAST_WRITE_LOCK:
metrics.AddTrainingTimeSaved(
api_label=_CHECKPOINT_V1,
microseconds=_get_duration_microseconds(_END_TIME_OF_LAST_WRITE,
end_time))
if checkpoint_context.in_preemption_save_context():
_preemption_checkpoint_saved_time_usecs.get_cell().increase_by(
_get_duration_microseconds(_END_TIME_OF_LAST_WRITE, end_time)
)
_END_TIME_OF_LAST_WRITE = end_time
if tensor_util.is_tf_type(output):
# Convert to numpy if not `tf.function` building.
if context.executing_eagerly():
output = compat.as_str(output.numpy())
else:
# Graph + Session, so we already session.ran it.
output = compat.as_str(output)
# Execute callbacks
if (options is not None and
options.experimental_write_callbacks is not None):
_execute_callbacks(options.experimental_write_callbacks, output)
metrics.RecordCheckpointSize(
api_label=_CHECKPOINT_V1, filesize=_get_checkpoint_size(output))
return output
@property
def save_counter(self):
"""An integer variable which starts at zero and is incremented on save.
Used to number checkpoints.
Returns:
The save counter variable.
"""
self._maybe_create_save_counter()
return self._save_counter
def save(self, file_prefix, session=None, options=None):
"""Saves a training checkpoint and provides basic checkpoint management.
The saved checkpoint includes variables created by this object and any
trackable objects it depends on at the time `Checkpoint.save()` is
called.
`save` is a basic convenience wrapper around the `write` method,
sequentially numbering checkpoints using `save_counter` and updating the
metadata used by `tf.train.latest_checkpoint`. More advanced checkpoint
management, for example garbage collection and custom numbering, may be
provided by other utilities which also wrap `write`
(`tf.train.CheckpointManager` for example).
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix). Names are generated based on this
prefix and `Checkpoint.save_counter`.
session: The session to evaluate variables in. Ignored when executing
eagerly. If not provided when graph building, the default session is
used.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint.
"""
graph_building = not context.executing_eagerly()
if graph_building:
if ops.inside_function():
raise NotImplementedError(
"Calling tf.train.Checkpoint.save() from a function is not "
"supported, as save() modifies saving metadata in ways not "
"supported by TensorFlow Operations. Consider using "
"tf.train.Checkpoint.write(), a lower-level API which does not "
"update metadata. tf.train.latest_checkpoint and related APIs will "
"not see this checkpoint.")
if session is None:
session = get_session()
if self._save_counter is None:
# When graph building, if this is a new save counter variable then it
# needs to be initialized before assign_add. This is only an issue if
# restore() has not been called first.
session.run(self.save_counter.initializer)
if not graph_building or self._save_assign_op is None:
with ops.colocate_with(self.save_counter):
assign_op = self.save_counter.assign_add(1, read_value=True)
if graph_building:
self._save_assign_op = data_structures.NoDependency(assign_op)
if graph_building:
checkpoint_number = session.run(self._save_assign_op)
else:
checkpoint_number = assign_op.numpy()
file_path = self.write(
"%s-%d" % (file_prefix, checkpoint_number),
session=session,
options=options
)
checkpoint_management.update_checkpoint_state_internal(
save_dir=os.path.dirname(file_prefix),
model_checkpoint_path=file_path,
all_model_checkpoint_paths=[file_path],
save_relative_paths=True)
return file_path
def restore(self, save_path):
"""Restore a training checkpoint.
Restores this `Checkpoint` and any objects it depends on.
When executing eagerly, either assigns values immediately if variables to
restore have been created already, or defers restoration until the variables
are created. Dependencies added after this call will be matched if they have
a corresponding object in the checkpoint (the restore request will queue in
any trackable object waiting for the expected dependency to be added).
When graph building, restoration ops are added to the graph but not run
immediately.
```python
checkpoint = tf.train.Checkpoint( ... )
checkpoint.restore(path)
```
To ensure that loading is complete and no more deferred restorations will
take place, you can use the `assert_consumed()` method of the status object
returned by `restore`.
The assert will raise an exception if any Python objects in the dependency
graph were not found in the checkpoint, or if any checkpointed values do not
have a matching Python object:
```python
checkpoint = tf.train.Checkpoint( ... )
checkpoint.restore(path).assert_consumed()
```
When graph building, `assert_consumed()` indicates that all of the restore
ops that will be created for this checkpoint have been created. They can be
run via the `run_restore_ops()` method of the status object:
```python
checkpoint.restore(path).assert_consumed().run_restore_ops()
```
If the checkpoint has not been consumed completely, then the list of restore
ops will grow as more objects are added to the dependency graph.
To check that all variables in the Python object have restored values from
checkpoint, use `assert_existing_objects_matched()`. This assertion is
useful when called after the variables in your graph have been created.
Name-based `tf.compat.v1.train.Saver` checkpoints can be loaded using this
method. Names are used to match variables. No restore ops are created/run
until `run_restore_ops()` or `initialize_or_restore()` are called on the
returned status object when graph building, but there is restore-on-creation
when executing eagerly. Re-encode name-based checkpoints using
`tf.train.Checkpoint.save` as soon as possible.
Args:
save_path: The path to the checkpoint, as returned by `save` or
`tf.train.latest_checkpoint`. If None (as when there is no latest
checkpoint for `tf.train.latest_checkpoint` to return), returns an
object which may run initializers for objects in the dependency graph.
If the checkpoint was written by the name-based
`tf.compat.v1.train.Saver`, names are used to match variables.
Returns:
A load status object, which can be used to make assertions about the
status of a checkpoint restoration and run initialization/restore ops.
The returned status object has the following methods:
* `assert_consumed()`:
Raises an exception if any variables are unmatched: either
checkpointed values which don't have a matching Python object or
Python objects in the dependency graph with no values in the
checkpoint. This method returns the status object, and so may be
chained with `initialize_or_restore` or `run_restore_ops`.
* `assert_existing_objects_matched()`:
Raises an exception if any existing Python objects in the dependency
graph are unmatched. Unlike `assert_consumed`, this assertion will
pass if values in the checkpoint have no corresponding Python
objects. For example a `tf.keras.Layer` object which has not yet been
built, and so has not created any variables, will pass this assertion
but will fail `assert_consumed`. Useful when loading part of a larger
checkpoint into a new Python program, e.g. a training checkpoint with
a `tf.compat.v1.train.Optimizer` was saved but only the state required
for inference is being loaded. This method returns the status object,
and so may be chained with `initialize_or_restore` or
`run_restore_ops`.
* `assert_nontrivial_match()`: Asserts that something aside from the root
object was matched. This is a very weak assertion, but is useful for
sanity checking in library code where objects may exist in the
checkpoint which haven't been created in Python and some Python
objects may not have a checkpointed value.
* `expect_partial()`: Silence warnings about incomplete checkpoint
restores. Warnings are otherwise printed for unused parts of the
checkpoint file or object when the `Checkpoint` object is deleted
(often at program shutdown).
* `initialize_or_restore(session=None)`:
When graph building, runs variable initializers if `save_path` is
`None`, but otherwise runs restore operations. If no `session` is
explicitly specified, the default session is used. No effect when
executing eagerly (variables are initialized or restored eagerly).
* `run_restore_ops(session=None)`:
When graph building, runs restore operations. If no `session` is
explicitly specified, the default session is used. No effect when
executing eagerly (restore operations are run eagerly). May only be
called when `save_path` is not `None`.
"""
start_time = time.time()
status = self._saver.restore(save_path=save_path)
# Create the save counter now so it gets initialized with other variables
# when graph building. Creating it earlier would lead to errors when using,
# say, train.Saver() to save the model before initializing it.
self._maybe_create_save_counter()
if isinstance(status, NameBasedSaverStatus):
status.add_to_optionally_restored(self.save_counter)
metrics.AddCheckpointReadDuration(
api_label=_CHECKPOINT_V1,
microseconds=_get_duration_microseconds(start_time, time.time()))
return status
@tf_export("train.Checkpoint", v1=[])
class Checkpoint(autotrackable.AutoTrackable):
"""Manages saving/restoring trackable values to disk.
TensorFlow objects may contain trackable state, such as `tf.Variable`s,
`tf.keras.optimizers.Optimizer` implementations, `tf.data.Dataset` iterators,
`tf.keras.Layer` implementations, or `tf.keras.Model` implementations.
These are called **trackable objects**.
A `Checkpoint` object can be constructed to save either a single or group of
trackable objects to a checkpoint file. It maintains a `save_counter` for
numbering checkpoints.
Example:
```python
model = tf.keras.Model(...)
checkpoint = tf.train.Checkpoint(model)
# Save a checkpoint to /tmp/training_checkpoints-{save_counter}. Every time
# checkpoint.save is called, the save counter is increased.
save_path = checkpoint.save('/tmp/training_checkpoints')
# Restore the checkpointed values to the `model` object.
checkpoint.restore(save_path)
```
Example 2:
```python
import tensorflow as tf
import os
checkpoint_directory = "/tmp/training_checkpoints"
checkpoint_prefix = os.path.join(checkpoint_directory, "ckpt")
# Create a Checkpoint that will manage two objects with trackable state,
# one we name "optimizer" and the other we name "model".
checkpoint = tf.train.Checkpoint(optimizer=optimizer, model=model)
status = checkpoint.restore(tf.train.latest_checkpoint(checkpoint_directory))
for _ in range(num_training_steps):
optimizer.minimize( ... ) # Variables will be restored on creation.
status.assert_consumed() # Optional sanity checks.
checkpoint.save(file_prefix=checkpoint_prefix)
```
`Checkpoint.save()` and `Checkpoint.restore()` write and read object-based
checkpoints, in contrast to TensorFlow 1.x's `tf.compat.v1.train.Saver` which
writes and
reads `variable.name` based checkpoints. Object-based checkpointing saves a
graph of dependencies between Python objects (`Layer`s, `Optimizer`s,
`Variable`s, etc.) with named edges, and this graph is used to match variables
when restoring a checkpoint. It can be more robust to changes in the Python
program, and helps to support restore-on-create for variables.
`Checkpoint` objects have dependencies on the objects passed as keyword
arguments to their constructors, and each dependency is given a name that is
identical to the name of the keyword argument for which it was created.
TensorFlow classes like `Layer`s and `Optimizer`s will automatically add
dependencies on their own variables (e.g. "kernel" and "bias" for
`tf.keras.layers.Dense`). Inheriting from `tf.keras.Model` makes managing
dependencies easy in user-defined classes, since `Model` hooks into attribute
assignment. For example:
```python
class Regress(tf.keras.Model):
def __init__(self):
super().__init__()
self.input_transform = tf.keras.layers.Dense(10)
# ...
def call(self, inputs):
x = self.input_transform(inputs)
# ...
```
This `Model` has a dependency named "input_transform" on its `Dense` layer,
which in turn depends on its variables. As a result, saving an instance of
`Regress` using `tf.train.Checkpoint` will also save all the variables created
by the `Dense` layer.
When variables are assigned to multiple workers, each worker writes its own
section of the checkpoint. These sections are then merged/re-indexed to behave
as a single checkpoint. This avoids copying all variables to one worker, but
does require that all workers see a common filesystem.
This function differs slightly from the Keras Model `save_weights` function.
`tf.keras.Model.save_weights` creates a checkpoint file with the name
specified in `filepath`, while `tf.train.Checkpoint` numbers the checkpoints,
using `filepath` as the prefix for the checkpoint file names. Aside from this,
`model.save_weights()` and `tf.train.Checkpoint(model).save()` are equivalent.
See the [guide to training
checkpoints](https://www.tensorflow.org/guide/checkpoint) for
details.
Attributes:
save_counter: Incremented when `save()` is called. Used to number
checkpoints.
"""
def __init__(self, root=None, **kwargs):
"""Creates a training checkpoint for a single or group of objects.
Args:
root: The root object to checkpoint. `root` may be a trackable object or
`WeakRef` of a trackable object.
**kwargs: Keyword arguments are set as attributes of this object, and are
saved with the checkpoint. All `kwargs` must be trackable objects, or a
nested structure of trackable objects (`list`, `dict`, or `tuple`).
Raises:
ValueError: If `root` or the objects in `kwargs` are not trackable. A
`ValueError` is also raised if the `root` object tracks different
objects from the ones listed in attributes in kwargs (e.g.
`root.child = A` and `tf.train.Checkpoint(root, child=B)` are
incompatible).
"""
super().__init__()
global _END_TIME_OF_LAST_WRITE
with _END_TIME_OF_LAST_WRITE_LOCK:
if _END_TIME_OF_LAST_WRITE is None:
_END_TIME_OF_LAST_WRITE = time.time()
# Store a reference to root and kwargs if we need to instantiate an
# AsyncCheckpointer later.
self._root = root
self._kwargs = kwargs
self._delete_tracking("_kwargs")
# Don't instantiate the AsyncCheckpointer unless required.
self._async_checkpointer_impl = None
# Store checkpoint options during the save/write calls so that subsequent
# read/restore calls are done properly. This is only populated when
# async read/write is enabled.
self._checkpoint_options = None
attached_dependencies = None
self._save_counter = None # Created lazily for restore-on-create.
self._save_assign_op = None
if root:
trackable_root = root() if isinstance(root, weakref.ref) else root
_assert_trackable(trackable_root, "root")
attached_dependencies = []
# All keyword arguments (including root itself) are set as children
# of root.
kwargs["root"] = root
trackable_root._maybe_initialize_trackable()
self._save_counter = data_structures.NoDependency(
trackable_root._lookup_dependency("save_counter"))
for k, v in sorted(kwargs.items(), key=lambda item: item[0]):
setattr(self, k, v)
# Call getattr instead of directly using v because setattr converts
# v to a Trackable data structure when v is a list/dict/tuple.
converted_v = getattr(self, k)
if isinstance(converted_v, weakref.ref):
converted_v = converted_v()
_assert_trackable(converted_v, k)
if root:
# Make sure that root doesn't already have dependencies with these names
child = trackable_root._lookup_dependency(k)
if child is None:
attached_dependencies.append(
base.WeakTrackableReference(k, converted_v))
elif child != converted_v:
raise ValueError(
f"Cannot create a Checkpoint with keyword argument {k} if "
f"root.{k} already exists.")
self._saver = TrackableSaver(
graph_view_lib.ObjectGraphView(
root if root else self,
attached_dependencies=attached_dependencies))
self._attached_dependencies = data_structures.NoDependency(
attached_dependencies)
def _maybe_create_save_counter(self):
"""Create a save counter if it does not yet exist."""
if self._save_counter is None:
# Initialized to 0 and incremented before saving.
with ops.device("/cpu:0"):
# add_variable creates a dependency named "save_counter"; NoDependency
# prevents creating a second dependency named "_save_counter".
self._save_counter = data_structures.NoDependency(
add_variable(
self,
name="save_counter",
initializer=0,
dtype=dtypes.int64,
trainable=False))
if self._attached_dependencies is not None:
self._attached_dependencies.append(
# Store a stronge reference to the `save_counter`, so that if the
# `Checkpoint` object is deleted, the `save_counter` does not get
# deleted immediately. (The LoadStatus object needs to indirectly
# reference the counter through the ObjectGraphView).
base.TrackableReference("save_counter", self._save_counter))
# When loading a checkpoint, the save counter is created after
# the checkpoint has been loaded, so it must be handled in a deferred
# manner.
if isinstance(self.root, weakref.ref):
root = self.root()
else:
root = self.root
restore = root._deferred_dependencies.pop("save_counter", ()) # pylint: disable=protected-access
if restore:
restore[0].restore(self._save_counter)
def write(self, file_prefix, options=None):
"""Writes a training checkpoint.
The checkpoint includes variables created by this object and any
trackable objects it depends on at the time `Checkpoint.write()` is
called.
`write` does not number checkpoints, increment `save_counter`, or update the
metadata used by `tf.train.latest_checkpoint`. It is primarily intended for
use by higher level checkpoint management utilities. `save` provides a very
basic implementation of these features.
Checkpoints written with `write` must be read with `read`.
Example usage:
```
step = tf.Variable(0, name="step")
checkpoint = tf.Checkpoint(step=step)
checkpoint.write("/tmp/ckpt")
# Later, read the checkpoint with read()
checkpoint.read("/tmp/ckpt")
# You can also pass options to write() and read(). For example this
# runs the IO ops on the localhost:
options = tf.CheckpointOptions(experimental_io_device="/job:localhost")
checkpoint.write("/tmp/ckpt", options=options)
# Later, read the checkpoint with read()
checkpoint.read("/tmp/ckpt", options=options)
```
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix).
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint (i.e. `file_prefix`).
"""
if isinstance(file_prefix, os.PathLike):
file_prefix = os.fspath(file_prefix)
return self._write(file_prefix, options)
def _async_checkpointer(self):
"""Returns an instantiated AsyncCheckpointHelper."""
if self._async_checkpointer_impl is None:
self._async_checkpointer_impl = (
async_checkpoint_helper.AsyncCheckpointHelper(
Checkpoint,
**self._kwargs))
return self._async_checkpointer_impl
def _write(self, file_prefix, options=None):
"""Internal method that implements Checkpoint.write().
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix).
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint (i.e. `file_prefix`).
"""
# Triggers TF2 async checkpoint handling if:
# 1. async checkpoint is enabled in CheckpointOptions
# 2. running in eager mode
if options and options.experimental_enable_async_checkpoint:
self._checkpoint_options = options
if checkpoint_context.in_preemption_save_context():
# Make sure all in-progress writes have completed before saving the
# final preemption checkpoint.
if self._async_checkpointer_impl is not None:
self._async_checkpointer_impl.sync()
# Additional work done will not be saved in a future checkpoint, so
# we use regular sync checkpoint to avoid overhead of dispatching
# checkpoint write to a new thread.
logging.warning(
"Switching to regular sync checkpoint for preemption checkpoint."
)
elif context.executing_eagerly():
return self._async_checkpointer()._write( # pylint: disable=protected-access
file_prefix, options)
else:
logging.warning(
"Saving async checkpoint in graph mode is currently not supported;"
" switching to regular sync checkpoint instead.")
start_time = time.time()
options = options or checkpoint_options.CheckpointOptions()
output = self._saver.save(file_prefix=file_prefix, options=options)
output = _convert_file_name_tensor_to_string(output)
# Execute callbacks (the only place they are executed; i.e. all entry points
# for callbacks will ultimately be directed to here for execution)
if options.experimental_write_callbacks:
_execute_callbacks(options.experimental_write_callbacks, output)
# Ensure save operations have completed when running in eager runtime.
if context.executing_eagerly():
context.async_wait()
end_time = time.time()
if not checkpoint_context.in_async_metrics_context():
# This records the time checkpoint._write() blocks on the main thread.
metrics.AddCheckpointWriteDuration(
api_label=_CHECKPOINT_V2,
microseconds=_get_duration_microseconds(start_time, end_time),
)
global _END_TIME_OF_LAST_WRITE
with _END_TIME_OF_LAST_WRITE_LOCK:
if not checkpoint_context.in_async_metrics_context():
metrics.AddTrainingTimeSaved(
api_label=_CHECKPOINT_V2,
microseconds=_get_duration_microseconds(
_END_TIME_OF_LAST_WRITE, end_time)
)
if checkpoint_context.in_preemption_save_context():
_preemption_checkpoint_saved_time_usecs.get_cell().increase_by(
_get_duration_microseconds(_END_TIME_OF_LAST_WRITE, end_time)
)
_END_TIME_OF_LAST_WRITE = end_time
metrics.RecordCheckpointSize(
api_label=_CHECKPOINT_V2, filesize=_get_checkpoint_size(output)
)
return output
@property
def save_counter(self):
"""An integer variable which starts at zero and is incremented on save.
Used to number checkpoints.
Returns:
The save counter variable.
"""
self._maybe_create_save_counter()
return self._save_counter
def sync(self):
"""Wait for any outstanding save or restore operations."""
# Subclasses of Checkpoint may not have `_async_checkpointer_impl` so use
# `getattr` for safer check.
if getattr(self, "_async_checkpointer_impl", None) is not None:
self._async_checkpointer_impl.sync()
def save(self, file_prefix, options=None):
# pylint:disable=line-too-long
"""Saves a training checkpoint and provides basic checkpoint management.
The saved checkpoint includes variables created by this object and any
trackable objects it depends on at the time `Checkpoint.save()` is
called.
`save` is a basic convenience wrapper around the `write` method,
sequentially numbering checkpoints using `save_counter` and updating the
metadata used by `tf.train.latest_checkpoint`. More advanced checkpoint
management, for example garbage collection and custom numbering, may be
provided by other utilities which also wrap `write` and `read`.
(`tf.train.CheckpointManager` for example).
```
step = tf.Variable(0, name="step")
checkpoint = tf.train.Checkpoint(step=step)
checkpoint.save("/tmp/ckpt")
# Later, read the checkpoint with restore()
checkpoint.restore("/tmp/ckpt-1")
# You can also pass options to save() and restore(). For example this
# runs the IO ops on the localhost:
options = tf.train.CheckpointOptions(experimental_io_device="/job:localhost")
checkpoint.save("/tmp/ckpt", options=options)
# Later, read the checkpoint with restore()
checkpoint.restore("/tmp/ckpt-1", options=options)
```
Args:
file_prefix: A prefix to use for the checkpoint filenames
(/path/to/directory/and_a_prefix). Names are generated based on this
prefix and `Checkpoint.save_counter`.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
The full path to the checkpoint.
"""
# Triggers TF2 async checkpoint handling if:
# 1. async checkpoint is enabled in CheckpointOptions
# 2. running in eager mode
if options and options.experimental_enable_async_checkpoint:
self._checkpoint_options = options
if checkpoint_context.in_preemption_save_context():
# Make sure all in-progress writes have completed before saving the
# final preemption checkpoint.
if self._async_checkpointer_impl is not None:
self._async_checkpointer_impl.sync()
# Additional work done will not be saved in a future checkpoint, so
# we use regular sync checkpoint to avoid overhead of dispatching
# checkpoint write to a new thread.
logging.warning(
"Switching to regular sync checkpoint for preemption checkpoint."
)
elif context.executing_eagerly():
return self._async_checkpointer().save(file_prefix, options)
else:
logging.warning(
"Saving async checkpoint in graph mode is currently not supported;"
" switching to regular sync checkpoint instead.")
if isinstance(file_prefix, os.PathLike):
file_prefix = os.fspath(file_prefix)
# pylint:enable=line-too-long
# We create a copy so that user's `options` instance would not be mutated
# by internal mechanisms.
options = copy.copy(options) or checkpoint_options.CheckpointOptions()
graph_building = not context.executing_eagerly()
if graph_building:
if ops.inside_function():
raise NotImplementedError(
"Calling tf.train.Checkpoint.save() from a function is not "
"supported, as save() modifies saving metadata in ways not "
"supported by TensorFlow Operations. Consider using "
"tf.train.Checkpoint.write(), a lower-level API which does not "
"update metadata. tf.train.latest_checkpoint and related APIs will "
"not see this checkpoint.")
session = get_session()
if self._save_counter is None:
# When graph building, if this is a new save counter variable then it
# needs to be initialized before assign_add. This is only an issue if
# restore() has not been called first.
session.run(self.save_counter.initializer)
if not graph_building or self._save_assign_op is None:
with ops.colocate_with(self.save_counter):
assign_op = self.save_counter.assign_add(1, read_value=True)
if graph_building:
self._save_assign_op = data_structures.NoDependency(assign_op)
if graph_building:
checkpoint_number = session.run(self._save_assign_op)
else:
checkpoint_number = assign_op.numpy()
if options.experimental_write_callbacks is None:
options.experimental_write_callbacks = [_update_checkpoint_state_internal]
else:
options.experimental_write_callbacks.append(
_update_checkpoint_state_internal
)
return self._write(
"%s-%d" % (file_prefix, checkpoint_number),
options=options)
def read(self, save_path, options=None):
"""Reads a training checkpoint written with `write`.
Reads this `Checkpoint` and any objects it depends on.
This method is just like `restore()` but does not expect the `save_counter`
variable in the checkpoint. It only restores the objects that the checkpoint
already depends on.
The method is primarily intended for use by higher level checkpoint
management utilities that use `write()` instead of `save()` and have their
own mechanisms to number and track checkpoints.
Example usage:
```python
# Create a checkpoint with write()
ckpt = tf.train.Checkpoint(v=tf.Variable(1.))
path = ckpt.write('/tmp/my_checkpoint')
# Later, load the checkpoint with read()
# With restore() assert_consumed() would have failed.
checkpoint.read(path).assert_consumed()
# You can also pass options to read(). For example this
# runs the IO ops on the localhost:
options = tf.train.CheckpointOptions(
experimental_io_device="/job:localhost")
checkpoint.read(path, options=options)
```
Args:
save_path: The path to the checkpoint as returned by `write`.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
A load status object, which can be used to make assertions about the
status of a checkpoint restoration. See `restore` for details.
"""
if options and options.experimental_enable_async_checkpoint:
self._checkpoint_options = options
# Triggers TF2 async checkpoint handling if:
# 1. async checkpoint is enabled in CheckpointOptions
# 2. there's a preceeding async save/write
# 3. running in eager mode
if (self._checkpoint_options and
self._checkpoint_options.experimental_enable_async_checkpoint):
if context.executing_eagerly():
return self._async_checkpointer().read(save_path, options)
else:
logging.warning(
"Saving async checkpoint in graph mode is currently not supported;"
" switching to regular sync checkpoint instead.")
start_time = time.time()
if isinstance(save_path, os.PathLike):
save_path = os.fspath(save_path)
options = options or checkpoint_options.CheckpointOptions()
result = self._saver.restore(save_path=save_path, options=options)
metrics.AddCheckpointReadDuration(
api_label=_CHECKPOINT_V2,
microseconds=_get_duration_microseconds(start_time, time.time()))
return result
def restore(self, save_path, options=None):
"""Restores a training checkpoint.
Restores this `Checkpoint` and any objects it depends on.
This method is intended to be used to load checkpoints created by `save()`.
For checkpoints created by `write()` use the `read()` method which does not
expect the `save_counter` variable added by `save()`.
`restore()` either assigns values immediately if variables to restore have
been created already, or defers restoration until the variables are
created. Dependencies added after this call will be matched if they have a
corresponding object in the checkpoint (the restore request will queue in
any trackable object waiting for the expected dependency to be added).
```python
checkpoint = tf.train.Checkpoint( ... )
checkpoint.restore(path)
# You can additionally pass options to restore():
options = tf.CheckpointOptions(experimental_io_device="/job:localhost")
checkpoint.restore(path, options=options)
```
To ensure that loading is complete and no more deferred restorations will
take place, use the `assert_consumed()` method of the status object returned
by `restore()`:
```python
checkpoint.restore(path, options=options).assert_consumed()
```
The assert will raise an error if any Python objects in the dependency graph
were not found in the checkpoint, or if any checkpointed values do not have
a matching Python object.
Name-based `tf.compat.v1.train.Saver` checkpoints from TensorFlow 1.x can be
loaded using this method. Names are used to match variables. Re-encode
name-based checkpoints using `tf.train.Checkpoint.save` as soon as possible.
**Loading from SavedModel checkpoints**
To load values from a SavedModel, just pass the SavedModel directory
to checkpoint.restore:
```python
model = tf.keras.Model(...)
tf.saved_model.save(model, path) # or model.save(path, save_format='tf')
checkpoint = tf.train.Checkpoint(model)
checkpoint.restore(path).expect_partial()
```
This example calls `expect_partial()` on the loaded status, since
SavedModels saved from Keras often generates extra keys in the checkpoint.
Otherwise, the program prints a lot of warnings about unused keys at exit
time.
Args:
save_path: The path to the checkpoint, as returned by `save` or
`tf.train.latest_checkpoint`. If the checkpoint was written by the
name-based `tf.compat.v1.train.Saver`, names are used to match
variables. This path may also be a SavedModel directory.
options: Optional `tf.train.CheckpointOptions` object.
Returns:
A load status object, which can be used to make assertions about the
status of a checkpoint restoration.
The returned status object has the following methods:
* `assert_consumed()`:
Raises an exception if any variables are unmatched: either
checkpointed values which don't have a matching Python object or
Python objects in the dependency graph with no values in the
checkpoint. This method returns the status object, and so may be
chained with other assertions.
* `assert_existing_objects_matched()`:
Raises an exception if any existing Python objects in the dependency
graph are unmatched. Unlike `assert_consumed`, this assertion will
pass if values in the checkpoint have no corresponding Python
objects. For example a `tf.keras.Layer` object which has not yet been
built, and so has not created any variables, will pass this assertion
but fail `assert_consumed`. Useful when loading part of a larger
checkpoint into a new Python program, e.g. a training checkpoint with
a `tf.compat.v1.train.Optimizer` was saved but only the state required
for
inference is being loaded. This method returns the status object, and
so may be chained with other assertions.
* `assert_nontrivial_match()`: Asserts that something aside from the root
object was matched. This is a very weak assertion, but is useful for
sanity checking in library code where objects may exist in the
checkpoint which haven't been created in Python and some Python
objects may not have a checkpointed value.
* `expect_partial()`: Silence warnings about incomplete checkpoint
restores. Warnings are otherwise printed for unused parts of the
checkpoint file or object when the `Checkpoint` object is deleted
(often at program shutdown).
Raises:
NotFoundError: if the a checkpoint or SavedModel cannot be found at
`save_path`.
"""
if options and options.experimental_enable_async_checkpoint:
self._checkpoint_options = options
# Triggers TF2 async checkpoint handling if:
# 1. async checkpoint is enabled in CheckpointOptions
# 2. there's a preceeding async save/write
# 3. running in eager mode
if (self._checkpoint_options and
self._checkpoint_options.experimental_enable_async_checkpoint):
if context.executing_eagerly():
return self._async_checkpointer().restore(save_path, options)
else:
logging.warning(
"Saving async checkpoint in graph mode is currently not supported;"
" switching to regular sync checkpoint instead.")
orig_save_path = save_path
if isinstance(save_path, os.PathLike):
save_path = os.fspath(save_path)
if save_path is not None and gfile.IsDirectory(save_path) and (
(gfile.Exists(path_helpers.get_saved_model_pb_path(save_path)) or
gfile.Exists(path_helpers.get_saved_model_pbtxt_path(save_path)))):
save_path = path_helpers.get_variables_path(save_path)
try:
status = self.read(save_path, options=options)
if context.executing_eagerly():
context.async_wait() # Ensure restore operations have completed.
except errors_impl.NotFoundError as e:
raise errors_impl.NotFoundError(
None, None,
f"Error when restoring from checkpoint or SavedModel at "
f"{orig_save_path}: {e.message}"
f"\nPlease double-check that the path is correct. You may be missing "
"the checkpoint suffix (e.g. the '-1' in 'path/to/ckpt-1').")
# Create the save counter now so it gets initialized with other variables
# when graph building. Creating it earlier would lead to errors when using,
# say, train.Saver() to save the model before initializing it.
self._maybe_create_save_counter()
if isinstance(status, NameBasedSaverStatus):
status.add_to_optionally_restored(self.save_counter)
return status
_preemption_checkpoint_saved_time_usecs = monitoring.Counter(
"/tensorflow/api/distribution_strategy/preemption_checkpoint_saved_time_usecs",
"Training time saved by PreemptionCheckpointHandler (us).")