View source on GitHub
|
Sequential groups a linear stack of layers into a tf.keras.Model.
Inherits From: Model, Layer, Module
tf.keras.Sequential(
layers=None, name=None
)
Sequential provides training and inference features on this model.
Examples:
# Optionally, the first layer can receive an `input_shape` argument:
model = tf.keras.Sequential()
model.add(tf.keras.layers.Dense(8, input_shape=(16,)))
# Afterwards, we do automatic shape inference:
model.add(tf.keras.layers.Dense(4))
# This is identical to the following:
model = tf.keras.Sequential()
model.add(tf.keras.Input(shape=(16,)))
model.add(tf.keras.layers.Dense(8))
# Note that you can also omit the `input_shape` argument.
# In that case the model doesn't have any weights until the first call
# to a training/evaluation method (since it isn't yet built):
model = tf.keras.Sequential()
model.add(tf.keras.layers.Dense(8))
model.add(tf.keras.layers.Dense(4))
# model.weights not created yet
# Whereas if you specify the input shape, the model gets built
# continuously as you are adding layers:
model = tf.keras.Sequential()
model.add(tf.keras.layers.Dense(8, input_shape=(16,)))
model.add(tf.keras.layers.Dense(4))
len(model.weights)
# Returns "4"
# When using the delayed-build pattern (no input shape specified), you can
# choose to manually build your model by calling
# `build(batch_input_shape)`:
model = tf.keras.Sequential()
model.add(tf.keras.layers.Dense(8))
model.add(tf.keras.layers.Dense(4))
model.build((None, 16))
len(model.weights)
# Returns "4"
# Note that when using the delayed-build pattern (no input shape specified),
# the model gets built the first time you call `fit`, `eval`, or `predict`,
# or the first time you call the model on some input data.
model = tf.keras.Sequential()
model.add(tf.keras.layers.Dense(8))
model.add(tf.keras.layers.Dense(1))
model.compile(optimizer='sgd', loss='mse')
# This builds the model for the first time:
model.fit(x, y, batch_size=32, epochs=10)
Args | |
|---|---|
layers
|
Optional list of layers to add to the model. |
name
|
Optional name for the model. |
Attributes | |
|---|---|
distribute_strategy
|
The tf.distribute.Strategy this model was created under.
|
layers
|
|
metrics_names
|
Returns the model's display labels for all outputs.
|
run_eagerly
|
Settable attribute indicating whether the model should run eagerly.
Running eagerly means that your model will be run step by step, like Python code. Your model might run slower, but it should become easier for you to debug it by stepping into individual layer calls. By default, we will attempt to compile your model to a static graph to deliver the best execution performance. |
Methods
add
add(
layer
)
Adds a layer instance on top of the layer stack.
| Args | |
|---|---|
layer
|
layer instance. |
| Raises | |
|---|---|
TypeError
|
If layer is not a layer instance.
|
ValueError
|
In case the layer argument does not
know its input shape.
|
ValueError
|
In case the layer argument has
multiple output tensors, or is already connected
somewhere else (forbidden in Sequential models).
|
compile
compile(
optimizer='rmsprop',
loss=None,
metrics=None,
loss_weights=None,
weighted_metrics=None,
run_eagerly=None,
steps_per_execution=None,
**kwargs
)
Configures the model for training.
Example:
model.compile(optimizer=tf.keras.optimizers.Adam(learning_rate=1e-3),
loss=tf.keras.losses.BinaryCrossentropy(),
metrics=[tf.keras.metrics.BinaryAccuracy(),
tf.keras.metrics.FalseNegatives()])
| Args | |
|---|---|
optimizer
|
String (name of optimizer) or optimizer instance. See
tf.keras.optimizers.
|
loss
|
Loss function. Maybe be a string (name of loss function), or
a tf.keras.losses.Loss instance. See tf.keras.losses. A loss
function is any callable with the signature loss = fn(y_true,
y_pred), where y_true are the ground truth values, and
y_pred are the model's predictions.
y_true should have shape
(batch_size, d0, .. dN) (except in the case of
sparse loss functions such as
sparse categorical crossentropy which expects integer arrays of shape
(batch_size, d0, .. dN-1)).
y_pred should have shape (batch_size, d0, .. dN).
The loss function should return a float tensor.
If a custom Loss instance is
used and reduction is set to None, return value has shape
(batch_size, d0, .. dN-1) i.e. per-sample or per-timestep loss
values; otherwise, it is a scalar. If the model has multiple outputs,
you can use a different loss on each output by passing a dictionary
or a list of losses. The loss value that will be minimized by the
model will then be the sum of all individual losses, unless
loss_weights is specified.
|
metrics
|
List of metrics to be evaluated by the model during training
and testing. Each of this can be a string (name of a built-in
function), function or a tf.keras.metrics.Metric instance. See
tf.keras.metrics. Typically you will use metrics=['accuracy']. A
function is any callable with the signature result = fn(y_true,
y_pred). To specify different metrics for different outputs of a
multi-output model, you could also pass a dictionary, such as
metrics={'output_a': 'accuracy', 'output_b': ['accuracy', 'mse']}.
You can also pass a list to specify a metric or a list of metrics
for each output, such as metrics=[['accuracy'], ['accuracy', 'mse']]
or metrics=['accuracy', ['accuracy', 'mse']]. When you pass the
strings 'accuracy' or 'acc', we convert this to one of
tf.keras.metrics.BinaryAccuracy,
tf.keras.metrics.CategoricalAccuracy,
tf.keras.metrics.SparseCategoricalAccuracy based on the loss
function used and the model output shape. We do a similar
conversion for the strings 'crossentropy' and 'ce' as well.
|
loss_weights
|
Optional list or dictionary specifying scalar coefficients
(Python floats) to weight the loss contributions of different model
outputs. The loss value that will be minimized by the model will then
be the weighted sum of all individual losses, weighted by the
loss_weights coefficients.
If a list, it is expected to have a 1:1 mapping to the model's
outputs. If a dict, it is expected to map output names (strings)
to scalar coefficients.
|
weighted_metrics
|
List of metrics to be evaluated and weighted by
sample_weight or class_weight during training and testing.
|
run_eagerly
|
Bool. Defaults to False. If True, this Model's
logic will not be wrapped in a tf.function. Recommended to leave
this as None unless your Model cannot be run inside a
tf.function. run_eagerly=True is not supported when using
tf.distribute.experimental.ParameterServerStrategy.
|
steps_per_execution
|
Int. Defaults to 1. The number of batches to
run during each tf.function call. Running multiple batches
inside a single tf.function call can greatly improve performance
on TPUs or small models with a large Python overhead.
At most, one full epoch will be run each
execution. If a number larger than the size of the epoch is passed,
the execution will be truncated to the size of the epoch.
Note that if steps_per_execution is set to N,
Callback.on_batch_begin and Callback.on_batch_end methods
will only be called every N batches
(i.e. before/after each tf.function execution).
|
**kwargs
|
Arguments supported for backwards compatibility only. |
evaluate
evaluate(
x=None,
y=None,
batch_size=None,
verbose=1,
sample_weight=None,
steps=None,
callbacks=None,
max_queue_size=10,
workers=1,
use_multiprocessing=False,
return_dict=False,
**kwargs
)
Returns the loss value & metrics values for the model in test mode.
Computation is done in batches (see the batch_size arg.)
| Args | |
|---|---|
x
|
Input data. It could be:
|
y
|
Target data. Like the input data x, it could be either Numpy
array(s) or TensorFlow tensor(s). It should be consistent with x
(you cannot have Numpy inputs and tensor targets, or inversely). If
x is a dataset, generator or keras.utils.Sequence instance, y
should not be specified (since targets will be obtained from the
iterator/dataset).
|
batch_size
|
Integer or None. Number of samples per batch of
computation. If unspecified, batch_size will default to 32. Do not
specify the batch_size if your data is in the form of a dataset,
generators, or keras.utils.Sequence instances (since they generate
batches).
|
verbose
|
0 or 1. Verbosity mode. 0 = silent, 1 = progress bar. |
sample_weight
|
Optional Numpy array of weights for the test samples,
used for weighting the loss function. You can either pass a flat (1D)
Numpy array with the same length as the input samples
(1:1 mapping between weights and samples), or in the case of
temporal data, you can pass a 2D array with shape (samples,
sequence_length), to apply a different weight to every timestep
of every sample. This argument is not supported when x is a
dataset, instead pass sample weights as the third element of x.
|
steps
|
Integer or None. Total number of steps (batches of samples)
before declaring the evaluation round finished. Ignored with the
default value of None. If x is a tf.data dataset and steps is
None, 'evaluate' will run until the dataset is exhausted. This
argument is not supported with array inputs.
|
callbacks
|
List of keras.callbacks.Callback instances. List of
callbacks to apply during evaluation. See
callbacks.
|
max_queue_size
|
Integer. Used for generator or keras.utils.Sequence
input only. Maximum size for the generator queue. If unspecified,
max_queue_size will default to 10.
|
workers
|
Integer. Used for generator or keras.utils.Sequence input
only. Maximum number of processes to spin up when using process-based
threading. If unspecified, workers will default to 1.
|
use_multiprocessing
|
Boolean. Used for generator or
keras.utils.Sequence input only. If True, use process-based
threading. If unspecified, use_multiprocessing will default to
False. Note that because this implementation relies on
multiprocessing, you should not pass non-picklable arguments to the
generator as they can't be passed easily to children processes.
|
return_dict
|
If True, loss and metric results are returned as a dict,
with each key being the name of the metric. If False, they are
returned as a list.
|
**kwargs
|
Unused at this time. |
See the discussion of Unpacking behavior for iterator-like inputs for
Model.fit.
Model.evaluate is not yet supported with
tf.distribute.experimental.ParameterServerStrategy.
| Returns | |
|---|---|
Scalar test loss (if the model has a single output and no metrics)
or list of scalars (if the model has multiple outputs
and/or metrics). The attribute model.metrics_names will give you
the display labels for the scalar outputs.
|
| Raises | |
|---|---|
RuntimeError
|
If model.evaluate is wrapped in a tf.function.
|
fit
fit(
x=None,
y=None,
batch_size=None,
epochs=1,
verbose='auto',
callbacks=None,
validation_split=0.0,
validation_data=None,
shuffle=True,
class_weight=None,
sample_weight=None,
initial_epoch=0,
steps_per_epoch=None,
validation_steps=None,
validation_batch_size=None,
validation_freq=1,
max_queue_size=10,
workers=1,
use_multiprocessing=False
)
Trains the model for a fixed number of epochs (iterations on a dataset).
| Args | |
|---|---|
x
|
Input data. It could be:
|
y
|
Target data. Like the input data x,
it could be either Numpy array(s) or TensorFlow tensor(s).
It should be consistent with x (you cannot have Numpy inputs and
tensor targets, or inversely). If x is a dataset, generator,
or keras.utils.Sequence instance, y should
not be specified (since targets will be obtained from x).
|
batch_size
|
Integer or None.
Number of samples per gradient update.
If unspecified, batch_size will default to 32.
Do not specify the batch_size if your data is in the
form of datasets, generators, or keras.utils.Sequence instances
(since they generate batches).
|
epochs
|
Integer. Number of epochs to train the model.
An epoch is an iteration over the entire x and y
data provided
(unless the steps_per_epoch flag is set to
something other than None).
Note that in conjunction with initial_epoch,
epochs is to be understood as "final epoch".
The model is not trained for a number of iterations
given by epochs, but merely until the epoch
of index epochs is reached.
|
verbose
|
'auto', 0, 1, or 2. Verbosity mode.
0 = silent, 1 = progress bar, 2 = one line per epoch.
'auto' defaults to 1 for most cases, but 2 when used with
ParameterServerStrategy. Note that the progress bar is not
particularly useful when logged to a file, so verbose=2 is
recommended when not running interactively (eg, in a production
environment).
|
callbacks
|
List of keras.callbacks.Callback instances.
List of callbacks to apply during training.
See tf.keras.callbacks. Note tf.keras.callbacks.ProgbarLogger
and tf.keras.callbacks.History callbacks are created automatically
and need not be passed into model.fit.
tf.keras.callbacks.ProgbarLogger is created or not based on
verbose argument to model.fit.
Callbacks with batch-level calls are currently unsupported with
tf.distribute.experimental.ParameterServerStrategy, and users are
advised to implement epoch-level calls instead with an appropriate
steps_per_epoch value.
|
validation_split
|
Float between 0 and 1.
Fraction of the training data to be used as validation data.
The model will set apart this fraction of the training data,
will not train on it, and will evaluate
the loss and any model metrics
on this data at the end of each epoch.
The validation data is selected from the last samples
in the x and y data provided, before shuffling. This argument is
not supported when x is a dataset, generator or
keras.utils.Sequence instance.
validation_split is not yet supported with
tf.distribute.experimental.ParameterServerStrategy.
|
validation_data
|
Data on which to evaluate
the loss and any model metrics at the end of each epoch.
The model will not be trained on this data. Thus, note the fact
that the validation loss of data provided using validation_split
or validation_data is not affected by regularization layers like
noise and dropout.
validation_data will override validation_split.
validation_data could be:
|
shuffle
|
Boolean (whether to shuffle the training data
before each epoch) or str (for 'batch'). This argument is ignored
when x is a generator or an object of tf.data.Dataset.
'batch' is a special option for dealing
with the limitations of HDF5 data; it shuffles in batch-sized
chunks. Has no effect when steps_per_epoch is not None.
|
class_weight
|
Optional dictionary mapping class indices (integers) to a weight (float) value, used for weighting the loss function (during training only). This can be useful to tell the model to "pay more attention" to samples from an under-represented class. |
sample_weight
|
Optional Numpy array of weights for
the training samples, used for weighting the loss function
(during training only). You can either pass a flat (1D)
Numpy array with the same length as the input samples
(1:1 mapping between weights and samples),
or in the case of temporal data,
you can pass a 2D array with shape
(samples, sequence_length),
to apply a different weight to every timestep of every sample. This
argument is not supported when x is a dataset, generator, or
keras.utils.Sequence instance, instead provide the sample_weights
as the third element of x.
|
initial_epoch
|
Integer. Epoch at which to start training (useful for resuming a previous training run). |
steps_per_epoch
|
Integer or None.
Total number of steps (batches of samples)
before declaring one epoch finished and starting the
next epoch. When training with input tensors such as
TensorFlow data tensors, the default None is equal to
the number of samples in your dataset divided by
the batch size, or 1 if that cannot be determined. If x is a
tf.data dataset, and 'steps_per_epoch'
is None, the epoch will run until the input dataset is exhausted.
When passing an infinitely repeating dataset, you must specify the
steps_per_epoch argument. If steps_per_epoch=-1 the training
will run indefinitely with an infinitely repeating dataset.
This argument is not supported with array inputs.
When using tf.distribute.experimental.ParameterServerStrategy:
steps_per_epoch=None is not supported.
|
validation_steps
|
Only relevant if validation_data is provided and
is a tf.data dataset. Total number of steps (batches of
samples) to draw before stopping when performing validation
at the end of every epoch. If 'validation_steps' is None, validation
will run until the validation_data dataset is exhausted. In the
case of an infinitely repeated dataset, it will run into an
infinite loop. If 'validation_steps' is specified and only part of
the dataset will be consumed, the evaluation will start from the
beginning of the dataset at each epoch. This ensures that the same
validation samples are used every time.
|
validation_batch_size
|
Integer or None.
Number of samples per validation batch.
If unspecified, will default to batch_size.
Do not specify the validation_batch_size if your data is in the
form of datasets, generators, or keras.utils.Sequence instances
(since they generate batches).
|
validation_freq
|
Only relevant if validation data is provided. Integer
or collections.abc.Container instance (e.g. list, tuple, etc.).
If an integer, specifies how many training epochs to run before a
new validation run is performed, e.g. validation_freq=2 runs
validation every 2 epochs. If a Container, specifies the epochs on
which to run validation, e.g. validation_freq=[1, 2, 10] runs
validation at the end of the 1st, 2nd, and 10th epochs.
|
max_queue_size
|
Integer. Used for generator or keras.utils.Sequence
input only. Maximum size for the generator queue.
If unspecified, max_queue_size will default to 10.
|
workers
|
Integer. Used for generator or keras.utils.Sequence input
only. Maximum number of processes to spin up
when using process-based threading. If unspecified, workers
will default to 1.
|
use_multiprocessing
|
Boolean. Used for generator or
keras.utils.Sequence input only. If True, use process-based
threading. If unspecified, use_multiprocessing will default to
False. Note that because this implementation relies on
multiprocessing, you should not pass non-picklable arguments to
the generator as they can't be passed easily to children processes.
|
Unpacking behavior for iterator-like inputs:
A common pattern is to pass a tf.data.Dataset, generator, or
tf.keras.utils.Sequence to the x argument of fit, which will in fact
yield not only features (x) but optionally targets (y) and sample weights.
Keras requires that the output of such iterator-likes be unambiguous. The
iterator should return a tuple of length 1, 2, or 3, where the optional
second and third elements will be used for y and sample_weight
respectively. Any other type provided will be wrapped in a length one
tuple, effectively treating everything as 'x'. When yielding dicts, they
should still adhere to the top-level tuple structure.
e.g. ({"x0": x0, "x1": x1}, y). Keras will not attempt to separate
features, targets, and weights from the keys of a single dict.
A notable unsupported data type is the namedtuple. The reason is that
it behaves like both an ordered datatype (tuple) and a mapping
datatype (dict). So given a namedtuple of the form:
namedtuple("example_tuple", ["y", "x"])
it is ambiguous whether to reverse the order of the elements when
interpreting the value. Even worse is a tuple of the form:
namedtuple("other_tuple", ["x", "y", "z"])
where it is unclear if the tuple was intended to be unpacked into x, y,
and sample_weight or passed through as a single element to x. As a
result the data processing code will simply raise a ValueError if it
encounters a namedtuple. (Along with instructions to remedy the issue.)
| Returns | |
|---|---|
A History object. Its History.history attribute is
a record of training loss values and metrics values
at successive epochs, as well as validation loss values
and validation metrics values (if applicable).
|
| Raises | |
|---|---|
RuntimeError
|
|
ValueError
|
In case of mismatch between the provided input data and what the model expects or when the input data is empty. |
get_layer
get_layer(
name=None, index=None
)
Retrieves a layer based on either its name (unique) or index.
If name and index are both provided, index will take precedence.
Indices are based on order of horizontal graph traversal (bottom-up).
| Args | |
|---|---|
name
|
String, name of layer. |
index
|
Integer, index of layer. |
| Returns | |
|---|---|
| A layer instance. |
load_weights
load_weights(
filepath, by_name=False, skip_mismatch=False, options=None
)
Loads all layer weights, either from a TensorFlow or an HDF5 weight file.
If by_name is False weights are loaded based on the network's
topology. This means the architecture should be the same as when the weights
were saved. Note that layers that don't have weights are not taken into
account in the topological ordering, so adding or removing layers is fine as
long as they don't have weights.
If by_name is True, weights are loaded into layers only if they share the
same name. This is useful for fine-tuning or transfer-learning models where
some of the layers have changed.
Only topological loading (by_name=False) is supported when loading weights
from the TensorFlow format. Note that topological loading differs slightly
between TensorFlow and HDF5 formats for user-defined classes inheriting from
tf.keras.Model: HDF5 loads based on a flattened list of weights, while the
TensorFlow format loads based on the object-local names of attributes to
which layers are assigned in the Model's constructor.
| Args | |
|---|---|
filepath
|
String, path to the weights file to load. For weight files in
TensorFlow format, this is the file prefix (the same as was passed
to save_weights). This can also be a path to a SavedModel
saved from model.save.
|
by_name
|
Boolean, whether to load weights by name or by topological order. Only topological loading is supported for weight files in TensorFlow format. |
skip_mismatch
|
Boolean, whether to skip loading of layers where there is
a mismatch in the number of weights, or a mismatch in the shape of
the weight (only valid when by_name=True).
|
options
|
Optional tf.train.CheckpointOptions object that specifies
options for loading weights.
|
| Returns | |
|---|---|
When loading a weight file in TensorFlow format, returns the same status
object as tf.train.Checkpoint.restore. When graph building, restore
ops are run automatically as soon as the network is built (on first call
for user-defined classes inheriting from Model, immediately if it is
already built).
When loading weights in HDF5 format, returns |
| Raises | |
|---|---|
ImportError
|
If h5py is not available and the weight file is in HDF5
format.
|
ValueError
|
If skip_mismatch is set to True when by_name is
False.
|
make_predict_function
make_predict_function(
force=False
)
Creates a function that executes one step of inference.
This method can be overridden to support custom inference logic.
This method is called by Model.predict and Model.predict_on_batch.
Typically, this method directly controls tf.function and
tf.distribute.Strategy settings, and delegates the actual evaluation
logic to Model.predict_step.
This function is cached the first time Model.predict or
Model.predict_on_batch is called. The cache is cleared whenever
Model.compile is called. You can skip the cache and generate again the
function with force=True.
| Args | |
|---|---|
force
|
Whether to regenerate the predict function and skip the cached function if available. |
| Returns | |
|---|---|
Function. The function created by this method should accept a
tf.data.Iterator, and return the outputs of the Model.
|
make_test_function
make_test_function(
force=False
)
Creates a function that executes one step of evaluation.
This method can be overridden to support custom evaluation logic.
This method is called by Model.evaluate and Model.test_on_batch.
Typically, this method directly controls tf.function and
tf.distribute.Strategy settings, and delegates the actual evaluation
logic to Model.test_step.
This function is cached the first time Model.evaluate or
Model.test_on_batch is called. The cache is cleared whenever
Model.compile is called. You can skip the cache and generate again the
function with force=True.
| Args | |
|---|---|
force
|
Whether to regenerate the test function and skip the cached function if available. |
| Returns | |
|---|---|
Function. The function created by this method should accept a
tf.data.Iterator, and return a dict containing values that will
be passed to tf.keras.Callbacks.on_test_batch_end.
|
make_train_function
make_train_function(
force=False
)
Creates a function that executes one step of training.
This method can be overridden to support custom training logic.
This method is called by Model.fit and Model.train_on_batch.
Typically, this method directly controls tf.function and
tf.distribute.Strategy settings, and delegates the actual training
logic to Model.train_step.
This function is cached the first time Model.fit or
Model.train_on_batch is called. The cache is cleared whenever
Model.compile is called. You can skip the cache and generate again the
function with force=True.
| Args | |
|---|---|
force
|
Whether to regenerate the train function and skip the cached function if available. |
| Returns | |
|---|---|
Function. The function created by this method should accept a
tf.data.Iterator, and return a dict containing values that will
be passed to tf.keras.Callbacks.on_train_batch_end, such as
{'loss': 0.2, 'accuracy': 0.7}.
|
pop
pop()
Removes the last layer in the model.
| Raises | |
|---|---|
TypeError
|
if there are no layers in the model. |
predict
predict(
x,
batch_size=None,
verbose=0,
steps=None,
callbacks=None,
max_queue_size=10,
workers=1,
use_multiprocessing=False
)
Generates output predictions for the input samples.
Computation is done in batches. This method is designed for performance in
large scale inputs. For small amount of inputs that fit in one batch,
directly using __call__() is recommended for faster execution, e.g.,
model(x), or model(x, training=False) if you have layers such as
tf.keras.layers.BatchNormalization that behaves differently during
inference. Also, note the fact that test loss is not affected by
regularization layers like noise and dropout.
| Args | |
|---|---|
x
|
Input samples. It could be:
|
batch_size
|
Integer or None.
Number of samples per batch.
If unspecified, batch_size will default to 32.
Do not specify the batch_size if your data is in the
form of dataset, generators, or keras.utils.Sequence instances
(since they generate batches).
|
verbose
|
Verbosity mode, 0 or 1. |
steps
|
Total number of steps (batches of samples)
before declaring the prediction round finished.
Ignored with the default value of None. If x is a tf.data
dataset and steps is None, predict() will
run until the input dataset is exhausted.
|
callbacks
|
List of keras.callbacks.Callback instances.
List of callbacks to apply during prediction.
See callbacks.
|
max_queue_size
|
Integer. Used for generator or keras.utils.Sequence
input only. Maximum size for the generator queue.
If unspecified, max_queue_size will default to 10.
|
workers
|
Integer. Used for generator or keras.utils.Sequence input
only. Maximum number of processes to spin up when using
process-based threading. If unspecified, workers will default
to 1.
|
use_multiprocessing
|
Boolean. Used for generator or
keras.utils.Sequence input only. If True, use process-based
threading. If unspecified, use_multiprocessing will default to
False. Note that because this implementation relies on
multiprocessing, you should not pass non-picklable arguments to
the generator as they can't be passed easily to children processes.
|
See the discussion of Unpacking behavior for iterator-like inputs for
Model.fit. Note that Model.predict uses the same interpretation rules as
Model.fit and Model.evaluate, so inputs must be unambiguous for all
three methods.
| Returns | |
|---|---|
| Numpy array(s) of predictions. |
| Raises | |
|---|---|
RuntimeError
|
If model.predict is wrapped in a tf.function.
|
ValueError
|
In case of mismatch between the provided input data and the model's expectations, or in case a stateful model receives a number of samples that is not a multiple of the batch size. |
predict_on_batch
predict_on_batch(
x
)
Returns predictions for a single batch of samples.
| Args | |
|---|---|
x
|
Input data. It could be:
|
| Returns | |
|---|---|
| Numpy array(s) of predictions. |
| Raises | |
|---|---|
RuntimeError
|
If model.predict_on_batch is wrapped in a tf.function.
|
predict_step
predict_step(
data
)
The logic for one inference step.
This method can be overridden to support custom inference logic.
This method is called by Model.make_predict_function.
This method should contain the mathematical logic for one step of inference. This typically includes the forward pass.
Configuration details for how this logic is run (e.g. tf.function and
tf.distribute.Strategy settings), should be left to
Model.make_predict_function, which can also be overridden.
| Args | |
|---|---|
data
|
A nested structure of Tensors.
|
| Returns | |
|---|---|
The result of one inference step, typically the output of calling the
Model on data.
|
reset_metrics
reset_metrics()
Resets the state of all the metrics in the model.
Examples:
inputs = tf.keras.layers.Input(shape=(3,))outputs = tf.keras.layers.Dense(2)(inputs)model = tf.keras.models.Model(inputs=inputs, outputs=outputs)model.compile(optimizer="Adam", loss="mse", metrics=["mae"])
x = np.random.random((2, 3))y = np.random.randint(0, 2, (2, 2))_ = model.fit(x, y, verbose=0)assert all(float(m.result()) for m in model.metrics)
model.reset_metrics()assert all(float(m.result()) == 0 for m in model.metrics)
reset_states
reset_states()
save
save(
filepath,
overwrite=True,
include_optimizer=True,
save_format=None,
signatures=None,
options=None,
save_traces=True
)
Saves the model to Tensorflow SavedModel or a single HDF5 file.
Please see tf.keras.models.save_model or the
Serialization and Saving guide
for details.
| Args | |
|---|---|
filepath
|
String, PathLike, path to SavedModel or H5 file to save the model. |
overwrite
|
Whether to silently overwrite any existing file at the target location, or provide the user with a manual prompt. |
include_optimizer
|
If True, save optimizer's state together. |
save_format
|
Either 'tf' or 'h5', indicating whether to save the
model to Tensorflow SavedModel or HDF5. Defaults to 'tf' in TF 2.X,
and 'h5' in TF 1.X.
|
signatures
|
Signatures to save with the SavedModel. Applicable to the
'tf' format only. Please see the signatures argument in
tf.saved_model.save for details.
|
options
|
(only applies to SavedModel format)
tf.saved_model.SaveOptions object that specifies options for
saving to SavedModel.
|
save_traces
|
(only applies to SavedModel format) When enabled, the
SavedModel will store the function traces for each layer. This
can be disabled, so that only the configs of each layer are stored.
Defaults to True. Disabling this will decrease serialization time
and reduce file size, but it requires that all custom layers/models
implement a get_config() method.
|
Example:
from keras.models import load_model
model.save('my_model.h5') # creates a HDF5 file 'my_model.h5'
del model # deletes the existing model
# returns a compiled model
# identical to the previous one
model = load_model('my_model.h5')
save_spec
save_spec(
dynamic_batch=True
)
Returns the tf.TensorSpec of call inputs as a tuple (args, kwargs).
This value is automatically defined after calling the model for the first time. Afterwards, you can use it when exporting the model for serving:
model = tf.keras.Model(...)
@tf.function
def serve(*args, **kwargs):
outputs = model(*args, **kwargs)
# Apply postprocessing steps, or add additional outputs.
...
return outputs
# arg_specs is `[tf.TensorSpec(...), ...]`. kwarg_specs, in this example, is
# an empty dict since functional models do not use keyword arguments.
arg_specs, kwarg_specs = model.save_spec()
model.save(path, signatures={
'serving_default': serve.get_concrete_function(*arg_specs, **kwarg_specs)
})
| Args | |
|---|---|
dynamic_batch
|
Whether to set the batch sizes of all the returned
tf.TensorSpec to None. (Note that when defining functional or
Sequential models with tf.keras.Input([...], batch_size=X), the
batch size will always be preserved). Defaults to True.
|
| Returns | |
|---|---|
If the model inputs are defined, returns a tuple (args, kwargs). All
elements in args and kwargs are tf.TensorSpec.
If the model inputs are not defined, returns None.
The model inputs are automatically set when calling the model,
model.fit, model.evaluate or model.predict.
|
save_weights
save_weights(
filepath, overwrite=True, save_format=None, options=None
)
Saves all layer weights.
Either saves in HDF5 or in TensorFlow format based on the save_format
argument.
When saving in HDF5 format, the weight file has:
layer_names(attribute), a list of strings (ordered names of model layers).- For every layer, a
groupnamedlayer.name- For every such layer group, a group attribute
weight_names, a list of strings (ordered names of weights tensor of the layer). - For every weight in the layer, a dataset storing the weight value, named after the weight tensor.
- For every such layer group, a group attribute
When saving in TensorFlow format, all objects referenced by the network are
saved in the same format as tf.train.Checkpoint, including any Layer
instances or Optimizer instances assigned to object attributes. For
networks constructed from inputs and outputs using tf.keras.Model(inputs,
outputs), Layer instances used by the network are tracked/saved
automatically. For user-defined classes which inherit from tf.keras.Model,
Layer instances must be assigned to object attributes, typically in the
constructor. See the documentation of tf.train.Checkpoint and
tf.keras.Model for details.
While the formats are the same, do not mix save_weights and
tf.train.Checkpoint. Checkpoints saved by Model.save_weights should be
loaded using Model.load_weights. Checkpoints saved using
tf.train.Checkpoint.save should be restored using the corresponding
tf.train.Checkpoint.restore. Prefer tf.train.Checkpoint over
save_weights for training checkpoints.
The TensorFlow format matches objects and variables by starting at a root
object, self for save_weights, and greedily matching attribute
names. For Model.save this is the Model, and for Checkpoint.save this
is the Checkpoint even if the Checkpoint has a model attached. 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
for details on the TensorFlow format.
| Args | |
|---|---|
filepath
|
String or PathLike, path to the file to save the weights to. When saving in TensorFlow format, this is the prefix used for checkpoint files (multiple files are generated). Note that the '.h5' suffix causes weights to be saved in HDF5 format. |
overwrite
|
Whether to silently overwrite any existing file at the target location, or provide the user with a manual prompt. |
save_format
|
Either 'tf' or 'h5'. A filepath ending in '.h5' or
'.keras' will default to HDF5 if save_format is None. Otherwise
None defaults to 'tf'.
|
options
|
Optional tf.train.CheckpointOptions object that specifies
options for saving weights.
|
| Raises | |
|---|---|
ImportError
|
If h5py is not available when attempting to save in HDF5
format.
|
summary
summary(
line_length=None, positions=None, print_fn=None, expand_nested=False
)
Prints a string summary of the network.
| Args | |
|---|---|
line_length
|
Total length of printed lines (e.g. set this to adapt the display to different terminal window sizes). |
positions
|
Relative or absolute positions of log elements
in each line. If not provided,
defaults to [.33, .55, .67, 1.].
|
print_fn
|
Print function to use. Defaults to print.
It will be called on each line of the summary.
You can set it to a custom function
in order to capture the string summary.
|
expand_nested
|
Whether to expand the nested models.
If not provided, defaults to False.
|
| Raises | |
|---|---|
ValueError
|
if summary() is called before the model is built.
|
test_on_batch
test_on_batch(
x, y=None, sample_weight=None, reset_metrics=True, return_dict=False
)
Test the model on a single batch of samples.
| Args | |
|---|---|
x
|
Input data. It could be:
|
y
|
Target data. Like the input data x, it could be either Numpy
array(s) or TensorFlow tensor(s). It should be consistent with x
(you cannot have Numpy inputs and tensor targets, or inversely).
|
sample_weight
|
Optional array of the same length as x, containing weights to apply to the model's loss for each sample. In the case of temporal data, you can pass a 2D array with shape (samples, sequence_length), to apply a different weight to every timestep of every sample. |
reset_metrics
|
If True, the metrics returned will be only for this
batch. If False, the metrics will be statefully accumulated across
batches.
|
return_dict
|
If True, loss and metric results are returned as a dict,
with each key being the name of the metric. If False, they are
returned as a list.
|
| Returns | |
|---|---|
Scalar test loss (if the model has a single output and no metrics)
or list of scalars (if the model has multiple outputs
and/or metrics). The attribute model.metrics_names will give you
the display labels for the scalar outputs.
|
| Raises | |
|---|---|
RuntimeError
|
If model.test_on_batch is wrapped in a tf.function.
|
test_step
test_step(
data
)
The logic for one evaluation step.
This method can be overridden to support custom evaluation logic.
This method is called by Model.make_test_function.
This function should contain the mathematical logic for one step of evaluation. This typically includes the forward pass, loss calculation, and metrics updates.
Configuration details for how this logic is run (e.g. tf.function and
tf.distribute.Strategy settings), should be left to
Model.make_test_function, which can also be overridden.
| Args | |
|---|---|
data
|
A nested structure of Tensors.
|
| Returns | |
|---|---|
A dict containing values that will be passed to
tf.keras.callbacks.CallbackList.on_train_batch_end. Typically, the
values of the Model's metrics are returned.
|
to_json
to_json(
**kwargs
)
Returns a JSON string containing the network configuration.
To load a network from a JSON save file, use
keras.models.model_from_json(json_string, custom_objects={}).
| Args | |
|---|---|
**kwargs
|
Additional keyword arguments
to be passed to json.dumps().
|
| Returns | |
|---|---|
| A JSON string. |
to_yaml
to_yaml(
**kwargs
)
Returns a yaml string containing the network configuration.
To load a network from a yaml save file, use
keras.models.model_from_yaml(yaml_string, custom_objects={}).
custom_objects should be a dictionary mapping
the names of custom losses / layers / etc to the corresponding
functions / classes.
| Args | |
|---|---|
**kwargs
|
Additional keyword arguments
to be passed to yaml.dump().
|
| Returns | |
|---|---|
| A YAML string. |
| Raises | |
|---|---|
RuntimeError
|
announces that the method poses a security risk |
train_on_batch
train_on_batch(
x,
y=None,
sample_weight=None,
class_weight=None,
reset_metrics=True,
return_dict=False
)
Runs a single gradient update on a single batch of data.
| Args | |
|---|---|
x
|
Input data. It could be:
|
y
|
Target data. Like the input data x, it could be either Numpy
array(s) or TensorFlow tensor(s). It should be consistent with x
(you cannot have Numpy inputs and tensor targets, or inversely).
|
sample_weight
|
Optional array of the same length as x, containing weights to apply to the model's loss for each sample. In the case of temporal data, you can pass a 2D array with shape (samples, sequence_length), to apply a different weight to every timestep of every sample. |
class_weight
|
Optional dictionary mapping class indices (integers) to a weight (float) to apply to the model's loss for the samples from this class during training. This can be useful to tell the model to "pay more attention" to samples from an under-represented class. |
reset_metrics
|
If True, the metrics returned will be only for this
batch. If False, the metrics will be statefully accumulated across
batches.
|
return_dict
|
If True, loss and metric results are returned as a dict,
with each key being the name of the metric. If False, they are
returned as a list.
|
| Returns | |
|---|---|
Scalar training loss
(if the model has a single output and no metrics)
or list of scalars (if the model has multiple outputs
and/or metrics). The attribute model.metrics_names will give you
the display labels for the scalar outputs.
|
| Raises | |
|---|---|
RuntimeError
|
If model.train_on_batch is wrapped in a tf.function.
|
train_step
train_step(
data
)
The logic for one training step.
This method can be overridden to support custom training logic.
For concrete examples of how to override this method see
Customizing what happends in fit.
This method is called by Model.make_train_function.
This method should contain the mathematical logic for one step of training. This typically includes the forward pass, loss calculation, backpropagation, and metric updates.
Configuration details for how this logic is run (e.g. tf.function and
tf.distribute.Strategy settings), should be left to
Model.make_train_function, which can also be overridden.
| Args | |
|---|---|
data
|
A nested structure of Tensors.
|
| Returns | |
|---|---|
A dict containing values that will be passed to
tf.keras.callbacks.CallbackList.on_train_batch_end. Typically, the
values of the Model's metrics are returned. Example:
{'loss': 0.2, 'accuracy': 0.7}.
|