View source on GitHub |
Exports a tf.Module (and subclasses) obj
to SavedModel format.
tf.saved_model.save(
obj,
export_dir: str,
signatures=None,
options: tf.saved_model.SaveOptions
= None
)
The obj
must inherit from the Trackable
class.
Example usage:
class Adder(tf.Module):
@tf.function(input_signature=[tf.TensorSpec(shape=[], dtype=tf.float32)])
def add(self, x):
return x + x
model = Adder()
tf.saved_model.save(model, '/tmp/adder')
The resulting SavedModel is then servable with an input named "x", a scalar with dtype float32.
Signatures
Signatures define the input and output types for a computation. The optional
save signatures
argument controls which methods in obj
will be
available to programs which consume SavedModel
s, for example, serving
APIs. Python functions may be decorated with
@tf.function(input_signature=...)
and passed as signatures directly, or
lazily with a call to get_concrete_function
on the method decorated with
@tf.function
.
Example:
class Adder(tf.Module):
@tf.function
def add(self, x):
return x + x
model = Adder()
tf.saved_model.save(
model, '/tmp/adder',signatures=model.add.get_concrete_function(
tf.TensorSpec([], tf.float32)))
If a @tf.function
does not have an input signature and
get_concrete_function
is not called on that method, the function will not
be directly callable in the restored SavedModel.
Example:
class Adder(tf.Module):
@tf.function
def add(self, x):
return x + x
model = Adder()
tf.saved_model.save(model, '/tmp/adder')
restored = tf.saved_model.load('/tmp/adder')
restored.add(1.)
Traceback (most recent call last):
ValueError: Found zero restored functions for caller function.
If the signatures
argument is omitted, obj
will be searched for
@tf.function
-decorated methods. If exactly one traced @tf.function
is
found, that method will be used as the default signature for the SavedModel.
Else, any @tf.function
attached to obj
or its dependencies will be
exported for use with tf.saved_model.load
.
When invoking a signature in an exported SavedModel, Tensor
arguments are
identified by name. These names will come from the Python function's argument
names by default. They may be overridden by specifying a name=...
argument
in the corresponding tf.TensorSpec
object. Explicit naming is required if
multiple Tensor
s are passed through a single argument to the Python
function.
The outputs of functions used as signatures
must either be flat lists, in
which case outputs will be numbered, or a dictionary mapping string keys to
Tensor
, in which case the keys will be used to name outputs.
Signatures are available in objects returned by tf.saved_model.load
as a
.signatures
attribute. This is a reserved attribute: tf.saved_model.save
on an object with a custom .signatures
attribute will raise an exception.
_Using tf.savedmodel.save
with Keras models
While Keras has its own saving and loading API, this function can be used to export Keras models. For example, exporting with a signature specified:
class Adder(tf.keras.Model):
@tf.function(input_signature=[tf.TensorSpec(shape=[], dtype=tf.string)])
def concat(self, x):
return x + x
model = Adder()
tf.saved_model.save(model, '/tmp/adder')
Exporting from a function without a fixed signature:
class Adder(tf.keras.Model):
@tf.function
def concat(self, x):
return x + x
model = Adder()
tf.saved_model.save(
model, '/tmp/adder',
signatures=model.concat.get_concrete_function(
tf.TensorSpec(shape=[], dtype=tf.string, name="string_input")))
tf.keras.Model
instances constructed from inputs and outputs already have a
signature and so do not require a @tf.function
decorator or a signatures
argument. If neither are specified, the model's forward pass is exported.
x = tf.keras.layers.Input((4,), name="x")
y = tf.keras.layers.Dense(5, name="out")(x)
model = tf.keras.Model(x, y)
tf.saved_model.save(model, '/tmp/saved_model/')
The exported SavedModel takes "x" with shape [None, 4] and returns "out" with shape [None, 5]
Variables and Checkpoints
Variables must be tracked by assigning them to an attribute of a tracked
object or to an attribute of obj
directly. TensorFlow objects (e.g. layers
from tf.keras.layers
, optimizers from tf.train
) track their variables
automatically. This is the same tracking scheme that tf.train.Checkpoint
uses, and an exported Checkpoint
object may be restored as a training
checkpoint by pointing tf.train.Checkpoint.restore
to the SavedModel's
"variables/" subdirectory.
tf.function
does not hard-code device annotations from outside the function
body, instead of using the calling context's device. This means for example
that exporting a model that runs on a GPU and serving it on a CPU will
generally work, with some exceptions:
tf.device
annotations inside the body of the function will be hard-coded in the exported model; this type of annotation is discouraged.- Device-specific operations, e.g. with "cuDNN" in the name or with device-specific layouts, may cause issues.
- For
ConcreteFunctions
, active distribution strategies will cause device placements to be hard-coded in the function.
SavedModels exported with tf.saved_model.save
strip default-valued
attributes
automatically, which removes one source of incompatibilities when the consumer
of a SavedModel is running an older TensorFlow version than the
producer. There are however other sources of incompatibilities which are not
handled automatically, such as when the exported model contains operations
which the consumer does not have definitions for.
Args | |
---|---|
obj
|
A trackable object (e.g. tf.Module or tf.train.Checkpoint) to export. |
export_dir
|
A directory in which to write the SavedModel. |
signatures
|
Optional, one of three types:
|
options
|
tf.saved_model.SaveOptions object for configuring save options.
|
Raises | |
---|---|
ValueError
|
If obj is not trackable.
|
eager compatibility
Not well supported when graph building. From TensorFlow 1.x,
tf.compat.v1.enable_eager_execution()
should run first. Calling
tf.saved_model.save in a loop when graph building from TensorFlow 1.x will
add new save operations to the default graph each iteration.
May not be called from within a function body.