adagrad.py

# Copyright (c) 2020 PaddlePaddle 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.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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from .optimizer import Optimizer
from ..fluid import core
from ..fluid import framework
from ..fluid.framework import Variable

__all__ = []


class Adagrad(Optimizer):
    r"""
    The Adaptive Gradient optimizer (Adagrad for short) use an optimization described
    in paper: `Adaptive Subgradient Methods for Online Learning and
    Stochastic Optimization <http://www.jmlr.org/papers/volume12/duchi11a/duchi11a.pdf>`_.

    The parameter ``param_out`` update rule with gradient ``grad``:

    .. math::

        moment\_out &= moment + grad * grad

        param\_out &= param - \frac{learning\_rate * grad}{\sqrt{moment\_out} + \epsilon}


    The original paper does not have the ``epsilon`` attribute. It is added here
    in our implementation as also proposed `Per-parameter adaptive learning rate
    methods <http://cs231n.github.io/neural-networks-3/#ada>`_
    for numerical stability to avoid the division by zero error.

    Args:
        learning_rate (float|Tensor): The learning rate used to update ``Parameter``.
            It can be a float value or a ``Variable`` with a float type.
        epsilon (float, optional): A small float value for numerical stability.
            The default value is 1e-06.
        parameters (list|tuple, optional): List/Tuple of ``Tensor`` to update to minimize ``loss``.
            This parameter is required in dygraph mode. And you can specify different options for
            different parameter groups such as the learning rate, weight decay, etc,
            then the parameters are list of dict. Note that the learning_rate in paramter groups
            represents the scale of base learning_rate.
            The default value is None in static mode, at this time all parameters will be updated.
        weight_decay (float|WeightDecayRegularizer, optional): The strategy of regularization.
            It canbe a float value as coeff of L2 regularization or
            :ref:`api_paddle_regularizer_L1Decay`, :ref:`api_paddle_regularizer_L2Decay`.
            If a parameter has set regularizer using :ref:`api_paddle_fluid_param_attr_aramAttr` already,
            the regularization setting here in optimizer will be ignored for this parameter.
            Otherwise, the regularization setting here in optimizer will take effect.
            Default None, meaning there is no regularization.
        grad_clip (GradientClipBase, optional): Gradient cliping strategy, it's an instance of
            some derived class of ``GradientClipBase`` . There are three cliping strategies,
            ClipGradByGlobalNorm, ClipGradByNorm and ClipGradByValue. Default None,
            meaning there is no gradient clipping.
        name (str, optional): Normally there is no need for user to set this property.
            For more information, please refer to :ref:`api_guide_Name`.
            The default value is None.
        initial_accumulator_value (float, optional): Initial value for moment accumulator.
            The default value is 0.0.

    Examples:
        .. code-block:: python

            import paddle
            import numpy as np

            inp = paddle.rand(shape=[10, 10])
            linear = paddle.nn.Linear(10, 10)
            out = linear(inp)
            loss = paddle.mean(out)
            adagrad = paddle.optimizer.Adagrad(learning_rate=0.1,
                    parameters=linear.parameters())
            out.backward()
            adagrad.step()
            adagrad.clear_grad()

            #Note that the learning_rate of linear_2 is 0.01.
            linear_1 = paddle.nn.Linear(10, 10)
            linear_2 = paddle.nn.Linear(10, 10)
            inp = paddle.uniform(shape=[10, 10], min=-0.1, max=0.1)
            out = linear_1(inp)
            out = linear_2(out)
            loss = paddle.mean(out)
            adagrad = paddle.optimizer.Adagrad(
                learning_rate=0.1,
                parameters=[{
                    'params': linear_1.parameters()
                }, {
                    'params': linear_2.parameters(),
                    'weight_decay': 0.001,
                    'learning_rate': 0.1,
                }],
                weight_decay=0.01)
            out.backward()
            adagrad.step()
            adagrad.clear_grad()

    """
    _moment_acc_str = "moment"

    def __init__(self,
                 learning_rate,
                 epsilon=1.0e-6,
                 parameters=None,
                 weight_decay=None,
                 grad_clip=None,
                 name=None,
                 initial_accumulator_value=0.0):
        assert learning_rate is not None
        assert epsilon is not None
        super(Adagrad, self).__init__(learning_rate=learning_rate,
                                      parameters=parameters,
                                      weight_decay=weight_decay,
                                      grad_clip=grad_clip,
                                      name=name)
        self.type = "adagrad"
        self._epsilon = epsilon
        self.initial_accumulator_value = initial_accumulator_value
        self._default_dict = {
            'epsilon': epsilon,
            'initial_accumulator_value': initial_accumulator_value,
        }

    def _create_accumulators(self, block, parameters):
        assert isinstance(block, framework.Block)

        if isinstance(parameters, dict):
            parameters = self._update_param_group(parameters)

        for p in parameters:
            self._add_accumulator(self._moment_acc_str,
                                  p,
                                  fill_value=self.initial_accumulator_value)

    def _append_optimize_op(self, block, param_and_grad):
        assert isinstance(block, framework.Block)

        if isinstance(param_and_grad, dict):
            param_and_grad = self._update_param_group(param_and_grad)

        moment_acc = self._get_accumulator(self._moment_acc_str,
                                           param_and_grad[0])
        # Create the adagrad optimizer op
        adagrad_op = block.append_op(type=self.type,
                                     inputs={
                                         "Param":
                                         param_and_grad[0],
                                         "Grad":
                                         param_and_grad[1],
                                         "Moment":
                                         moment_acc,
                                         "LearningRate":
                                         self._create_param_lr(param_and_grad)
                                     },
                                     outputs={
                                         "ParamOut": param_and_grad[0],
                                         "MomentOut": moment_acc
                                     },
                                     attrs={"epsilon": self._epsilon},
                                     stop_gradient=True)

        return adagrad_op

    def _update_param_group(self, parameters):
        self._epsilon = parameters.get('epsilon', self._default_dict['epsilon'])
        self.initial_accumulator_value = parameters.get(
            'initial_accumulator_value',
            self._default_dict['initial_accumulator_value'])
        parameters = parameters.get('params')
        return parameters