TensorFlow 2 version | View source on GitHub |
Exports the Trackable object obj
to SavedModel format.
tf.saved_model.save(
obj, export_dir, signatures=None
)
Example usage:
class Adder(tf.Module):
@tf.function(input_signature=[tf.TensorSpec(shape=None, dtype=tf.float32)])
def add(self, x):
return x + x + 1.
to_export = Adder()
tf.saved_model.save(to_export, '/tmp/adder')
The resulting SavedModel is then servable with an input named "x", its value having any shape and dtype float32.
The optional 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
.
If the signatures
argument is omitted, obj
will be searched for
@tf.function
-decorated methods. If exactly one @tf.function
is found, that
method will be used as the default signature for the SavedModel. This behavior
is expected to change in the future, when a corresponding
tf.saved_model.load
symbol is added. At that point signatures will be
completely optional, and any @tf.function
attached to obj
or its
dependencies will be exported for use with 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.
Since tf.keras.Model
objects are also Trackable, this function can be
used to export Keras models. For example, exporting with a signature
specified:
class Model(tf.keras.Model):
@tf.function(input_signature=[tf.TensorSpec(shape=[None], dtype=tf.string)])
def serve(self, serialized):
...
m = Model()
tf.saved_model.save(m, '/tmp/saved_model/')
Exporting from a function without a fixed signature:
class Model(tf.keras.Model):
@tf.function
def call(self, x):
...
m = Model()
tf.saved_model.save(
m, '/tmp/saved_model/',
signatures=m.call.get_concrete_function(
tf.TensorSpec(shape=[None, 3], dtype=tf.float32, name="inp")))
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 = input_layer.Input((4,), name="x")
y = core.Dense(5, name="out")(x)
model = training.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 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. Currently variables are the only stateful objects
supported by tf.saved_model.save
, but others (e.g. tables) will be supported
in the future.
tf.function
does not hard-code device annotations from outside the function
body, instead using the calling context's device. This means for example that
exporting a model which 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. Currently a DistributionStrategy
is another exception: active distribution strategies will cause device
placements to be hard-coded in a function. Exporting a single-device
computation and importing under a DistributionStrategy
is not currently
supported, but may be in the future.
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 to export. |
export_dir
|
A directory in which to write the SavedModel. |
signatures
|
Optional, either a tf.function with an input signature
specified or the result of f.get_concrete_function on a
@tf.function -decorated function f , in which case f will be used to
generate a signature for the SavedModel under the default serving
signature key. signatures may also be a dictionary, in which case it
maps from signature keys to either tf.function instances with input
signatures or concrete functions. The keys of such a dictionary may be
arbitrary strings, but will typically be from the
tf.saved_model.signature_constants module.
|
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.