# Copyright (c) 2018 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 # limitations under the License. import framework from . import core __all__ = [ 'append_regularization_ops', 'L1Decay', 'L2Decay', ] def append_regularization_ops(parameters_and_grads, regularization=None): """Create and add backward regularization Operators Creates and adds backward regularization operators in the BlockDesc. This will add gradients of the regularizer function to the gradients of the parameters and return these modified gradients. This is the same as implementing weight decay in optimizers for regularization. Args: parameters_and_grads: A list of (parameters, gradients) pairs that need to be regularized. regularization: A global regularizer. If the parameter is not set. It will be applied with regularizer. Returns: list of (parameters, gradients) pair with the regularized gradient Raises: Exception: Unknown regularization type """ params_and_grads = [] for param, grad in parameters_and_grads: # If no gradient then we don't need to do anything if grad is None: params_and_grads.append((param, grad)) continue regularization_term = None if param.regularizer is not None: # Add variable for regularization term in grad block regularization_term = param.regularizer(param, grad, grad.block) elif regularization is not None: regularization_term = regularization(param, grad, grad.block) # If no regularization specified, then we don't need to do anything if regularization_term is None: params_and_grads.append((param, grad)) continue assert grad.shape == regularization_term.shape grad.block.append_op( type='elementwise_add', inputs={"X": grad, "Y": regularization_term}, outputs={"Out": grad}) params_and_grads.append((param, grad)) return params_and_grads class WeightDecayRegularizer(object): """Base class for weight decay regularizers Defines the common interface of weight-decay regularizers. Weight-decay regularizers are added only during the backward pass for faster regularization. They add operations to the network that correspond to gradient of the regularization function. Users should not use this class directly, but need to use one of its implementations """ def __init__(self): pass def __call__(self, param, grad, block): """Add corresponding weight decay operations to the network """ raise NotImplementedError() def __str__(self): """Debug string """ raise NotImplementedError() class L2DecayRegularizer(WeightDecayRegularizer): """Implements the L2 Weight Decay Regularization """ def __init__(self, regularization_coeff=0.0): assert regularization_coeff is not None super(L2DecayRegularizer, self).__init__() self._regularization_coeff = regularization_coeff def __call__(self, param, grad, block): """Add L2 weight decay ops to network Adds L2 weight decay ops. L2WeightDecay = reg_coeff * parameter Args: param: parameter variable for which regularization is applied block: block in which variable is to be created Returns: new variable for weight decay """ assert isinstance(param, framework.Parameter) assert isinstance(block, framework.Block) decay = block.create_var( dtype="float32", shape=param.shape, lod_level=param.lod_level) if grad.type == core.VarDesc.VarType.SELECTED_ROWS: decay = block.create_var( dtype="float32", shape=param.shape, type=core.VarDesc.VarType.SELECTED_ROWS) block.append_op( type='lookup_table', inputs={'W': param, 'Ids': grad}, outputs={'Out': decay}, attrs={'is_sparse': True}) param = decay # Append Op to calculate decay block.append_op( type='scale', inputs={"X": param}, outputs={"Out": decay}, attrs={"scale": self._regularization_coeff}) return decay def __str__(self): return "L2Decay, regularization_coeff=%f" % self._regularization_coeff class L1DecayRegularizer(WeightDecayRegularizer): """Implements the L1 Weight Decay Regularization """ def __init__(self, regularization_coeff=0.0): assert regularization_coeff is not None super(L1DecayRegularizer, self).__init__() self._regularization_coeff = regularization_coeff def __call__(self, param, grad, block): """Add L1 weight decay ops to network Adds L1 weight decay ops. L1WeightDecay = reg_coeff * sign(parameter) Args: param: parameter variable for which regularization is applied block: block in which variable is to be created Returns: new variable for weight decay """ assert isinstance(param, framework.Parameter) assert isinstance(block, framework.Block) decay = block.create_var( dtype="float32", shape=param.shape, lod_level=param.lod_level) if grad.type == core.VarDesc.VarType.SELECTED_ROWS: decay = block.create_var( dtype="float32", shape=param.shape, type=core.VarDesc.VarType.SELECTED_ROWS) block.append_op( type='lookup_table', inputs={'W': param, 'Ids': grad}, outputs={'Out': decay}, attrs={'is_sparse': True}) # Append sign op block.append_op( type='sign', inputs={"X": param}, outputs={"Out": decay}) # Append scale op to the output of sign op block.append_op( type='scale', inputs={"X": decay}, outputs={"Out": decay}, attrs={"scale": self._regularization_coeff}) return decay def __str__(self): return "L1Decay, regularization_coeff=%f" % self._regularization_coeff # We short the class name, since users will use the regulaizer with the package # name. The sample code: # # import paddle.fluid as fluid # # hidden = fluid.layers.fc(..., # param_attr=fluid.regularizer.Xavier()) # # It is no need to add a `Regularizer` as the class suffix L1Decay = L1DecayRegularizer L2Decay = L2DecayRegularizer