Optimizer that implements the Adagrad algorithm.
Inherits From: Optimizer
tf.keras.optimizers.Adagrad(
learning_rate=0.001, initial_accumulator_value=0.1, epsilon=1e-07,
name='Adagrad', **kwargs
)
Adagrad is an optimizer with parameter-specific learning rates,
which are adapted relative to how frequently a parameter gets
updated during training. The more updates a parameter receives,
the smaller the updates.
Initialization:
$$accum_{g_0} := \text{initial_accumulator_value}$$
Update step:
$$t := t + 1$$
$$accum_{g_t} := accum_{g_{t-1} } + g^2$$
$$\theta_t := \theta_{t-1} - lr * g / (\sqrt{accum_{g_t} } + \epsilon)$$
References:
Args |
learning_rate
|
A Tensor or a floating point value. The learning rate.
|
initial_accumulator_value
|
A floating point value.
Starting value for the accumulators, must be non-negative.
|
epsilon
|
A small floating point value to avoid zero denominator.
|
name
|
Optional name prefix for the operations created when applying
gradients. Defaults to "Adagrad".
|
**kwargs
|
keyword arguments. Allowed to be {clipnorm , clipvalue , lr ,
decay }. clipnorm is clip gradients by norm; clipvalue is clip
gradients by value, decay is included for backward compatibility to
allow time inverse decay of learning rate. lr is included for backward
compatibility, recommended to use learning_rate instead.
|
Raises |
ValueError
|
If the initial_accumulator_value or epsilon is invalid.
|
Attributes |
iterations
|
Variable. The number of training steps this Optimizer has run.
|
weights
|
Returns variables of this Optimizer based on the order created.
|
Methods
add_slot
View source
add_slot(
var, slot_name, initializer='zeros'
)
Add a new slot variable for var
.
add_weight
View source
add_weight(
name, shape, dtype=None, initializer='zeros', trainable=None,
synchronization=tf.VariableSynchronization.AUTO,
aggregation=tf.compat.v1.VariableAggregation.NONE
)
apply_gradients
View source
apply_gradients(
grads_and_vars, name=None
)
Apply gradients to variables.
This is the second part of minimize()
. It returns an Operation
that
applies gradients.
Args |
grads_and_vars
|
List of (gradient, variable) pairs.
|
name
|
Optional name for the returned operation. Default to the name
passed to the Optimizer constructor.
|
Returns |
An Operation that applies the specified gradients. The iterations
will be automatically increased by 1.
|
Raises |
TypeError
|
If grads_and_vars is malformed.
|
ValueError
|
If none of the variables have gradients.
|
from_config
View source
@classmethod
from_config(
config, custom_objects=None
)
Creates an optimizer from its config.
This method is the reverse of get_config
,
capable of instantiating the same optimizer from the config
dictionary.
Arguments |
config
|
A Python dictionary, typically the output of get_config.
|
custom_objects
|
A Python dictionary mapping names to additional Python
objects used to create this optimizer, such as a function used for a
hyperparameter.
|
Returns |
An optimizer instance.
|
get_config
View source
get_config()
Returns the config of the optimimizer.
An optimizer config is a Python dictionary (serializable)
containing the configuration of an optimizer.
The same optimizer can be reinstantiated later
(without any saved state) from this configuration.
Returns |
Python dictionary.
|
get_gradients
View source
get_gradients(
loss, params
)
Returns gradients of loss
with respect to params
.
Arguments |
loss
|
Loss tensor.
|
params
|
List of variables.
|
Returns |
List of gradient tensors.
|
Raises |
ValueError
|
In case any gradient cannot be computed (e.g. if gradient
function not implemented).
|
get_slot
View source
get_slot(
var, slot_name
)
get_slot_names
View source
get_slot_names()
A list of names for this optimizer's slots.
get_updates
View source
get_updates(
loss, params
)
get_weights
View source
get_weights()
minimize
View source
minimize(
loss, var_list, grad_loss=None, name=None
)
Minimize loss
by updating var_list
.
This method simply computes gradient using tf.GradientTape
and calls
apply_gradients()
. If you want to process the gradient before applying
then call tf.GradientTape
and apply_gradients()
explicitly instead
of using this function.
Args |
loss
|
A callable taking no arguments which returns the value to minimize.
|
var_list
|
list or tuple of Variable objects to update to minimize
loss , or a callable returning the list or tuple of Variable objects.
Use callable when the variable list would otherwise be incomplete before
minimize since the variables are created at the first time loss is
called.
|
grad_loss
|
Optional. A Tensor holding the gradient computed for loss .
|
name
|
Optional name for the returned operation.
|
Returns |
An Operation that updates the variables in var_list . The iterations
will be automatically increased by 1.
|
Raises |
ValueError
|
If some of the variables are not Variable objects.
|
set_weights
View source
set_weights(
weights
)
variables
View source
variables()
Returns variables of this Optimizer based on the order created.