Module keras.optimizer_v2.adadelta

Adadelta optimizer implementation.

Expand source code
# Copyright 2018 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.
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#
#     http://www.apache.org/licenses/LICENSE-2.0
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# See the License for the specific language governing permissions and
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# ==============================================================================
"""Adadelta optimizer implementation."""

import tensorflow.compat.v2 as tf
# pylint: disable=g-classes-have-attributes

import numpy as np
from keras import backend_config
from keras.optimizer_v2 import optimizer_v2
from tensorflow.python.util.tf_export import keras_export


@keras_export('keras.optimizers.Adadelta')
class Adadelta(optimizer_v2.OptimizerV2):
  r"""Optimizer that implements the Adadelta algorithm.

  Adadelta optimization is a stochastic gradient descent method that is based on
  adaptive learning rate per dimension to address two drawbacks:

  - The continual decay of learning rates throughout training.
  - The need for a manually selected global learning rate.

  Adadelta is a more robust extension of Adagrad that adapts learning rates
  based on a moving window of gradient updates, instead of accumulating all
  past gradients. This way, Adadelta continues learning even when many updates
  have been done. Compared to Adagrad, in the original version of Adadelta you
  don't have to set an initial learning rate. In this version, the initial
  learning rate can be set, as in most other Keras optimizers.

  Args:
    learning_rate: Initial value for the learning rate:
      either a floating point value,
      or a `tf.keras.optimizers.schedules.LearningRateSchedule` instance.
      Defaults to 0.001.
      Note that `Adadelta` tends to benefit from higher initial learning rate
      values compared to other optimizers.
      To match the exact form in the original paper, use 1.0.
    rho: A `Tensor` or a floating point value. The decay rate.
    epsilon: Small floating point value used to maintain numerical stability.
    name: Optional name prefix for the operations created when applying
      gradients.  Defaults to `"Adadelta"`.
    **kwargs: Keyword arguments. Allowed to be one of
      `"clipnorm"` or `"clipvalue"`.
      `"clipnorm"` (float) clips gradients by norm and represents
      the maximum norm of each parameter;
      `"clipvalue"` (float) clips gradient by value and represents the
      maximum absolute value of each parameter.

  Reference:
    - [Zeiler, 2012](http://arxiv.org/abs/1212.5701)
  """

  _HAS_AGGREGATE_GRAD = True

  def __init__(self,
               learning_rate=0.001,
               rho=0.95,
               epsilon=1e-7,
               name='Adadelta',
               **kwargs):
    super(Adadelta, self).__init__(name, **kwargs)
    self._set_hyper('learning_rate', kwargs.get('lr', learning_rate))
    self._set_hyper('decay', self._initial_decay)
    self._set_hyper('rho', rho)
    self.epsilon = epsilon or backend_config.epsilon()

  def _create_slots(self, var_list):
    # Separate for-loops to respect the ordering of slot variables from v1.
    for v in var_list:
      self.add_slot(v, 'accum_grad')
    for v in var_list:
      self.add_slot(v, 'accum_var')

  def _prepare_local(self, var_device, var_dtype, apply_state):
    super(Adadelta, self)._prepare_local(var_device, var_dtype, apply_state)
    apply_state[(var_device, var_dtype)].update(
        dict(
            epsilon=tf.convert_to_tensor(
                self.epsilon, var_dtype),
            rho=tf.identity(self._get_hyper('rho', var_dtype))))

  def set_weights(self, weights):
    params = self.weights
    # Override set_weights for backward compatibility of Keras V1 optimizer
    # since it does not include iteration at head of the weight list. Set
    # iteration to 0.
    if len(params) == len(weights) + 1:
      weights = [np.array(0)] + weights
    super(Adadelta, self).set_weights(weights)

  def _resource_apply_dense(self, grad, var, apply_state=None):
    var_device, var_dtype = var.device, var.dtype.base_dtype
    coefficients = ((apply_state or {}).get((var_device, var_dtype))
                    or self._fallback_apply_state(var_device, var_dtype))

    accum_grad = self.get_slot(var, 'accum_grad')
    accum_var = self.get_slot(var, 'accum_var')
    return tf.raw_ops.ResourceApplyAdadelta(
        var=var.handle,
        accum=accum_grad.handle,
        accum_update=accum_var.handle,
        lr=coefficients['lr_t'],
        rho=coefficients['rho'],
        epsilon=coefficients['epsilon'],
        grad=grad,
        use_locking=self._use_locking)

  def _resource_apply_sparse(self, grad, var, indices, apply_state=None):
    var_device, var_dtype = var.device, var.dtype.base_dtype
    coefficients = ((apply_state or {}).get((var_device, var_dtype))
                    or self._fallback_apply_state(var_device, var_dtype))

    accum_grad = self.get_slot(var, 'accum_grad')
    accum_var = self.get_slot(var, 'accum_var')
    return tf.raw_ops.ResourceSparseApplyAdadelta(
        var=var.handle,
        accum=accum_grad.handle,
        accum_update=accum_var.handle,
        lr=coefficients['lr_t'],
        rho=coefficients['rho'],
        epsilon=coefficients['epsilon'],
        grad=grad,
        indices=indices,
        use_locking=self._use_locking)

  def get_config(self):
    config = super(Adadelta, self).get_config()
    config.update({
        'learning_rate': self._serialize_hyperparameter('learning_rate'),
        'decay': self._initial_decay,
        'rho': self._serialize_hyperparameter('rho'),
        'epsilon': self.epsilon,
    })
    return config

Classes

class Adadelta (learning_rate=0.001, rho=0.95, epsilon=1e-07, name='Adadelta', **kwargs)

Optimizer that implements the Adadelta algorithm.

Adadelta optimization is a stochastic gradient descent method that is based on adaptive learning rate per dimension to address two drawbacks:

  • The continual decay of learning rates throughout training.
  • The need for a manually selected global learning rate.

Adadelta is a more robust extension of Adagrad that adapts learning rates based on a moving window of gradient updates, instead of accumulating all past gradients. This way, Adadelta continues learning even when many updates have been done. Compared to Adagrad, in the original version of Adadelta you don't have to set an initial learning rate. In this version, the initial learning rate can be set, as in most other Keras optimizers.

Args

learning_rate
Initial value for the learning rate: either a floating point value, or a tf.keras.optimizers.schedules.LearningRateSchedule instance. Defaults to 0.001. Note that Adadelta tends to benefit from higher initial learning rate values compared to other optimizers. To match the exact form in the original paper, use 1.0.
rho
A Tensor or a floating point value. The decay rate.
epsilon
Small floating point value used to maintain numerical stability.
name
Optional name prefix for the operations created when applying gradients. Defaults to "Adadelta".
**kwargs
Keyword arguments. Allowed to be one of "clipnorm" or "clipvalue". "clipnorm" (float) clips gradients by norm and represents the maximum norm of each parameter; "clipvalue" (float) clips gradient by value and represents the maximum absolute value of each parameter.

Reference

Create a new Optimizer.

This must be called by the constructors of subclasses. Note that Optimizer instances should not bind to a single graph, and so shouldn't keep Tensors as member variables. Generally you should be able to use the _set_hyper()/state.get_hyper() facility instead.

This class is stateful and thread-compatible.

Example of custom gradient transformations:

def my_gradient_transformer(grads_and_vars):
  # Simple example, double the gradients.
  return [(2. * g, v) for g, v in grads_and_vars]

optimizer = tf.keras.optimizers.SGD(
    1e-3, gradient_transformers=[my_gradient_transformer])

Args

name
String. The name to use for momentum accumulator weights created by the optimizer.
gradient_aggregator
The function to use to aggregate gradients across devices (when using tf.distribute.Strategy). If None, defaults to summing the gradients across devices. The function should accept and return a list of (gradient, variable) tuples.
gradient_transformers
Optional. List of functions to use to transform gradients before applying updates to Variables. The functions are applied after gradient_aggregator. The functions should accept and return a list of (gradient, variable) tuples.
**kwargs
keyword arguments. Allowed arguments are clipvalue, clipnorm, global_clipnorm. If clipvalue (float) is set, the gradient of each weight is clipped to be no higher than this value. If clipnorm (float) is set, the gradient of each weight is individually clipped so that its norm is no higher than this value. If global_clipnorm (float) is set the gradient of all weights is clipped so that their global norm is no higher than this value.

Raises

ValueError
in case of any invalid argument.
Expand source code
class Adadelta(optimizer_v2.OptimizerV2):
  r"""Optimizer that implements the Adadelta algorithm.

  Adadelta optimization is a stochastic gradient descent method that is based on
  adaptive learning rate per dimension to address two drawbacks:

  - The continual decay of learning rates throughout training.
  - The need for a manually selected global learning rate.

  Adadelta is a more robust extension of Adagrad that adapts learning rates
  based on a moving window of gradient updates, instead of accumulating all
  past gradients. This way, Adadelta continues learning even when many updates
  have been done. Compared to Adagrad, in the original version of Adadelta you
  don't have to set an initial learning rate. In this version, the initial
  learning rate can be set, as in most other Keras optimizers.

  Args:
    learning_rate: Initial value for the learning rate:
      either a floating point value,
      or a `tf.keras.optimizers.schedules.LearningRateSchedule` instance.
      Defaults to 0.001.
      Note that `Adadelta` tends to benefit from higher initial learning rate
      values compared to other optimizers.
      To match the exact form in the original paper, use 1.0.
    rho: A `Tensor` or a floating point value. The decay rate.
    epsilon: Small floating point value used to maintain numerical stability.
    name: Optional name prefix for the operations created when applying
      gradients.  Defaults to `"Adadelta"`.
    **kwargs: Keyword arguments. Allowed to be one of
      `"clipnorm"` or `"clipvalue"`.
      `"clipnorm"` (float) clips gradients by norm and represents
      the maximum norm of each parameter;
      `"clipvalue"` (float) clips gradient by value and represents the
      maximum absolute value of each parameter.

  Reference:
    - [Zeiler, 2012](http://arxiv.org/abs/1212.5701)
  """

  _HAS_AGGREGATE_GRAD = True

  def __init__(self,
               learning_rate=0.001,
               rho=0.95,
               epsilon=1e-7,
               name='Adadelta',
               **kwargs):
    super(Adadelta, self).__init__(name, **kwargs)
    self._set_hyper('learning_rate', kwargs.get('lr', learning_rate))
    self._set_hyper('decay', self._initial_decay)
    self._set_hyper('rho', rho)
    self.epsilon = epsilon or backend_config.epsilon()

  def _create_slots(self, var_list):
    # Separate for-loops to respect the ordering of slot variables from v1.
    for v in var_list:
      self.add_slot(v, 'accum_grad')
    for v in var_list:
      self.add_slot(v, 'accum_var')

  def _prepare_local(self, var_device, var_dtype, apply_state):
    super(Adadelta, self)._prepare_local(var_device, var_dtype, apply_state)
    apply_state[(var_device, var_dtype)].update(
        dict(
            epsilon=tf.convert_to_tensor(
                self.epsilon, var_dtype),
            rho=tf.identity(self._get_hyper('rho', var_dtype))))

  def set_weights(self, weights):
    params = self.weights
    # Override set_weights for backward compatibility of Keras V1 optimizer
    # since it does not include iteration at head of the weight list. Set
    # iteration to 0.
    if len(params) == len(weights) + 1:
      weights = [np.array(0)] + weights
    super(Adadelta, self).set_weights(weights)

  def _resource_apply_dense(self, grad, var, apply_state=None):
    var_device, var_dtype = var.device, var.dtype.base_dtype
    coefficients = ((apply_state or {}).get((var_device, var_dtype))
                    or self._fallback_apply_state(var_device, var_dtype))

    accum_grad = self.get_slot(var, 'accum_grad')
    accum_var = self.get_slot(var, 'accum_var')
    return tf.raw_ops.ResourceApplyAdadelta(
        var=var.handle,
        accum=accum_grad.handle,
        accum_update=accum_var.handle,
        lr=coefficients['lr_t'],
        rho=coefficients['rho'],
        epsilon=coefficients['epsilon'],
        grad=grad,
        use_locking=self._use_locking)

  def _resource_apply_sparse(self, grad, var, indices, apply_state=None):
    var_device, var_dtype = var.device, var.dtype.base_dtype
    coefficients = ((apply_state or {}).get((var_device, var_dtype))
                    or self._fallback_apply_state(var_device, var_dtype))

    accum_grad = self.get_slot(var, 'accum_grad')
    accum_var = self.get_slot(var, 'accum_var')
    return tf.raw_ops.ResourceSparseApplyAdadelta(
        var=var.handle,
        accum=accum_grad.handle,
        accum_update=accum_var.handle,
        lr=coefficients['lr_t'],
        rho=coefficients['rho'],
        epsilon=coefficients['epsilon'],
        grad=grad,
        indices=indices,
        use_locking=self._use_locking)

  def get_config(self):
    config = super(Adadelta, self).get_config()
    config.update({
        'learning_rate': self._serialize_hyperparameter('learning_rate'),
        'decay': self._initial_decay,
        'rho': self._serialize_hyperparameter('rho'),
        'epsilon': self.epsilon,
    })
    return config

Ancestors

  • OptimizerV2
  • tensorflow.python.training.tracking.base.Trackable

Inherited members