# Copyright (c) 2016 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. from __future__ import print_function import math from .. import unique_name __all__ = [ 'NoamDecay', 'PiecewiseDecay', 'NaturalExpDecay', 'ExponentialDecay', 'InverseTimeDecay', 'PolynomialDecay', 'CosineDecay' ] class LearningRateDecay(object): """ Base class of learning rate decay Define the common interface of an LearningRateDecay. User should not use this class directly, but need to use one of it's implementation. """ def __init__(self, begin=0, step=1, dtype='float32'): self.step_num = begin self.step_size = step self.dtype = dtype def __call__(self): lr = self.step() if isinstance(lr, float): lr = self.create_lr_var(lr) self.step_num += self.step_size return lr def create_lr_var(self, lr): """ convert lr from float to variable Args: lr: learning rate Returns: learning rate variable """ from .. import layers lr = layers.create_global_var( name=unique_name.generate("learning_rate"), shape=[1], value=float(lr), dtype=self.dtype, persistable=False) return lr def step(self): raise NotImplementedError() class PiecewiseDecay(LearningRateDecay): """ Piecewise decay scheduler. The algorithm can be described as the code below. .. code-block:: text boundaries = [10000, 20000] values = [1.0, 0.5, 0.1] if global_step < 10000: learning_rate = 1.0 elif 10000 <= global_step < 20000: learning_rate = 0.5 else: learning_rate = 0.1 Parameters: boundaries(list): A list of steps numbers. The type of element in the list is python int. values(list): A list of learning rate values that will be picked during different step boundaries. The type of element in the list is python float. begin(int): The begin step to initialize the global_step in the description above. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. Returns: None. Examples: .. code-block:: python import paddle.fluid as fluid boundaries = [10000, 20000] values = [1.0, 0.5, 0.1] with fluid.dygraph.guard(): emb = fluid.dygraph.Embedding( [10, 10] ) optimizer = fluid.optimizer.SGD( learning_rate=fluid.dygraph.PiecewiseDecay(boundaries, values, 0), parameter_list = emb.parameters() ) """ def __init__(self, boundaries, values, begin, step=1, dtype='float32'): super(PiecewiseDecay, self).__init__(begin, step, dtype) self.boundaries = boundaries self.values = values self.vars = [] for value in values: self.vars.append(value) def step(self): for i in range(len(self.boundaries)): if self.step_num < self.boundaries[i]: return self.vars[i] return self.create_lr_var(self.vars[len(self.values) - 1]) class NaturalExpDecay(LearningRateDecay): """ Applies natural exponential decay to the initial learning rate. The algorithm can be described as following. .. math:: decayed\_learning\_rate = learning\_rate * e^{y} If staircase is set to False, then: .. math:: y = - decay\_rate * \\frac{global\_step}{decay\_steps} If staircase is set to True, then: .. math:: y = - decay\_rate * math.floor(\\frac{global\_step}{decay\_steps}) Parameters: learning_rate(Variable|float): The initial learning rate. If the type is Variable, it's a tensor with shape [1], the data type can be float32 or float64. It also can be set to python int number. decay_steps(int): The decay step size. It determines the decay cycle. decay_rate(int): The decay rate. staircase(bool, optional): If set to True, decay the learning rate at discrete intervals. The default value is False. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. Returns: None. Examples: .. code-block:: python import paddle.fluid as fluid base_lr = 0.1 with fluid.dygraph.guard(): sgd_optimizer = fluid.optimizer.SGD( learning_rate=fluid.dygraph.NaturalExpDecay( learning_rate=base_lr, decay_steps=10000, decay_rate=0.5, staircase=True)) """ def __init__(self, learning_rate, decay_steps, decay_rate, staircase=False, begin=0, step=1, dtype='float32'): super(NaturalExpDecay, self).__init__(begin, step, dtype) self.learning_rate = learning_rate self.decay_steps = decay_steps self.decay_rate = decay_rate self.staircase = staircase def step(self): from .. import layers div_res = self.create_lr_var(self.step_num / self.decay_steps) if self.staircase: div_res = layers.floor(div_res) decayed_lr = self.learning_rate * layers.exp(-1 * self.decay_rate * div_res) return decayed_lr class ExponentialDecay(LearningRateDecay): """ Applies exponential decay to the learning rate. The algorithm can be described as following. .. math:: decayed\_learning\_rate = learning\_rate * decay\_rate ^ y If staircase is set to False, then: .. math:: y = \\frac{global\_step}{decay\_steps} If staircase is set to True, then: .. math:: y = math.floor(\\frac{global\_step}{decay\_steps}) Parameters: learning_rate(Variable|float): The initial learning rate. If the type is Variable, it's a tensor with shape [1], the data type can be float32 or float64. It also can be set to python int number. decay_steps(int): The decay step size. It determines the decay cycle. decay_rate(float): The decay rate. staircase(bool, optional): If set to True, decay the learning rate at discrete intervals. The default value is False. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. Returns: None. Examples: .. code-block:: python import paddle.fluid as fluid base_lr = 0.1 with fluid.dygraph.guard(): sgd_optimizer = fluid.optimizer.SGD( learning_rate=fluid.dygraph.ExponentialDecay( learning_rate=base_lr, decay_steps=10000, decay_rate=0.5, staircase=True)) """ def __init__(self, learning_rate, decay_steps, decay_rate, staircase=False, begin=0, step=1, dtype='float32'): super(ExponentialDecay, self).__init__(begin, step, dtype) self.learning_rate = learning_rate self.decay_steps = decay_steps self.decay_rate = decay_rate self.staircase = staircase def step(self): from .. import layers div_res = self.create_lr_var(self.step_num / self.decay_steps) if self.staircase: div_res = layers.floor(div_res) decayed_lr = self.learning_rate * (self.decay_rate**div_res) return decayed_lr class InverseTimeDecay(LearningRateDecay): """ Applies inverse time decay to the initial learning rate. The algorithm can be described as following. If staircase is set to False, then: .. math:: decayed\_learning\_rate = \\frac{learning\_rate}{1 + decay\_rate * \\frac{global\_step}{decay\_step}} If staircase is set to True, then: .. math:: decayed\_learning\_rate = \\frac{learning\_rate}{1 + decay\_rate * math.floor(\\frac{global\_step}{decay\_step})} Parameters: learning_rate(Variable|float): The initial learning rate. If the type is Variable, it's a tensor with shape [1], the data type can be float32 or float64. It also can be set to python int number. decay_steps(int): The decay step size. It determines the decay cycle. decay_rate(float): The decay rate. staircase(bool, optional): If set to True, decay the learning rate at discrete intervals. The default value is False. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be 'float32', 'float64'. The default value is 'float32'. Returns: None. Examples: .. code-block:: python import paddle.fluid as fluid base_lr = 0.1 with fluid.dygraph.guard(): emb = fluid.dygraph.Embedding([10, 10]) sgd_optimizer = fluid.optimizer.SGD( learning_rate=fluid.dygraph.InverseTimeDecay( learning_rate=base_lr, decay_steps=10000, decay_rate=0.5, staircase=True), parameter_list = emb.parameters()) """ def __init__(self, learning_rate, decay_steps, decay_rate, staircase=False, begin=0, step=1, dtype='float32'): super(InverseTimeDecay, self).__init__(begin, step, dtype) self.learning_rate = learning_rate self.decay_steps = decay_steps self.decay_rate = decay_rate self.staircase = staircase def step(self): from .. import layers div_res = self.create_lr_var(self.step_num / self.decay_steps) if self.staircase: div_res = layers.floor(div_res) decayed_lr = self.learning_rate / (1 + self.decay_rate * div_res) return decayed_lr class PolynomialDecay(LearningRateDecay): """ Applies polynomial decay to the initial learning rate. The algorithm can be described as following. If cycle is set to True, then: .. math:: decay\_steps & = decay\_steps * math.ceil(\\frac{global\_step}{decay\_steps}) decayed\_learning\_rate & = (learning\_rate-end\_learning\_rate)*(1-\\frac{global\_step}{decay\_steps})^{power}+end\_learning\_rate If cycle is set to False, then: .. math:: global\_step & = min(global\_step, decay\_steps) decayed\_learning\_rate & = (learning\_rate-end\_learning\_rate)*(1-\\frac{global\_step}{decay\_steps})^{power}+end\_learning\_rate Parameters: learning_rate(Variable|float): The initial learning rate. If the type is Variable, it's a tensor with shape [1], the data type can be float32 or float64. It also can be set to python int number. decay_steps(int32): The decay step size. It determines the decay cycle. end_learning_rate(float, optional): The minimum final learning rate. The default value is 0.0001. power(float, optional): Power of polynomial. The default value is 1.0. cycle(bool, optional): If set true, decay the learning rate every decay_steps. The default value is False. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. Returns: None. Examples: .. code-block:: python import paddle.fluid as fluid start_lr = 0.01 total_step = 5000 end_lr = 0 with fluid.dygraph.guard(): emb = fluid.dygraph.Embedding( [10, 10]) optimizer = fluid.optimizer.SGD( learning_rate = fluid.dygraph.PolynomialDecay( start_lr, total_step, end_lr, power=1.0), parameter_list = emb.parameters()) """ def __init__(self, learning_rate, decay_steps, end_learning_rate=0.0001, power=1.0, cycle=False, begin=0, step=1, dtype='float32'): super(PolynomialDecay, self).__init__(begin, step, dtype) self.learning_rate = learning_rate self.decay_steps = decay_steps self.end_learning_rate = end_learning_rate self.power = power self.cycle = cycle def step(self): from .. import layers tmp_step_num = self.step_num tmp_decay_steps = self.decay_steps if self.cycle: div_res = layers.ceil( self.create_lr_var(tmp_step_num / float(self.decay_steps))) if tmp_step_num == 0: div_res = self.create_lr_var(1.0) tmp_decay_steps = self.decay_steps * div_res else: tmp_step_num = self.create_lr_var(tmp_step_num if tmp_step_num < self.decay_steps else self.decay_steps) decayed_lr = (self.learning_rate - self.end_learning_rate) * \ ((1 - tmp_step_num / tmp_decay_steps) ** self.power) + self.end_learning_rate return decayed_lr class CosineDecay(LearningRateDecay): """ Applies cosine decay to the learning rate. The algorithm can be described as following. .. math:: decayed\_learning\_rate = learning\_rate * 0.5 * (math.cos(global\_step * \\frac{math.pi}{step\_each\_epoch} ) + 1) Parameters: learning_rate(Variable|float): The initial learning rate. If the type is Variable, it's a tensor with shape [1], the data type can be float32 or float64. It also can be set to python int number. step_each_epoch(int): The number of steps in an epoch. epochs(int): The number of epochs. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. Returns: None. Examples: .. code-block:: python base_lr = 0.1 with fluid.dygraph.guard(): optimizer = fluid.optimizer.SGD( learning_rate = fluid.dygraph.CosineDecay( base_lr, 10000, 120) ) """ def __init__(self, learning_rate, step_each_epoch, epochs, begin=0, step=1, dtype='float32'): super(CosineDecay, self).__init__(begin, step, dtype) self.learning_rate = learning_rate self.step_each_epoch = step_each_epoch self.epochs = epochs def step(self): from .. import layers cur_epoch = layers.floor( self.create_lr_var(self.step_num / self.step_each_epoch)) decayed_lr = self.learning_rate * 0.5 * ( layers.cos(cur_epoch * math.pi / self.epochs) + 1) return decayed_lr class NoamDecay(LearningRateDecay): """ Applies Noam decay to the initial learning rate. The algorithm can be described as following. .. math:: decayed\_learning\_rate = learning\_rate * d_{model}^{-0.5} * min(global\_step^{-0.5}, global\_step * warmup\_steps^{-1.5}) Please reference `attention is all you need `_ Parameters: d$_{model}$(Variable|int): The dimensionality of input and output feature vector of model. If type is Variable, it's a tensor with shape [1] and the data type can be int32 or int64. The type can also be python int. warmup_steps(Variable|int): The number of warmup steps. A super parameter. If type is Variable, it's a tensor with shape [1] and the data type can be int32 or int64. The type can also be python int. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. learning_rate(Variable|float|int): The initial learning rate. If the type is Variable, it's a tensor with shape [1], the data type can be float32 or float64. It also can be set to python int number. Default 1.0 Returns: None. Examples: .. code-block:: python import paddle.fluid as fluid warmup_steps = 100 learning_rate = 0.01 with fluid.dygraph.guard(): emb = fluid.dygraph.Embedding([10, 10]) optimizer = fluid.optimizer.SGD( learning_rate = fluid.dygraph.NoamDecay( 1/(warmup_steps *(learning_rate ** 2)), warmup_steps), parameter_list = emb.parameters()) """ def __init__(self, d_model, warmup_steps, begin=1, step=1, dtype='float32', learning_rate=1.0): super(NoamDecay, self).__init__(begin, step, dtype) self.learning_rate = learning_rate self.d_model = d_model self.warmup_steps = warmup_steps def step(self): from .. import layers a = self.create_lr_var(self.step_num**-0.5) b = self.create_lr_var((self.warmup_steps**-1.5) * self.step_num) lr_value = self.learning_rate * (self.d_model **-0.5) * layers.elementwise_min(a, b) return lr_value class LinearLrWarmup(LearningRateDecay): """ This operator use the linear learning rate warm up strategy to adjust the learning rate preliminarily before the normal learning rate scheduling. For more information, please refer to `Bag of Tricks for Image Classification with Convolutional Neural Networks `_ When global_step < warmup_steps, learning rate is updated as: .. code-block:: text linear_step = end_lr - start_lr lr = start_lr + linear_step * (global_step / warmup_steps) where start_lr is the initial learning rate, and end_lr is the final learning rate; When global_step >= warmup_steps, learning rate is updated as: .. code-block:: text lr = learning_rate where lr is the learning_rate after warm-up. Args: learning_rate (Variable|float): Learning_rate after warm-up, it could be 1D-Tensor or single value with the data type of float32. warmup_steps (int): Steps for warm up. start_lr (float): Initial learning rate of warm up. end_lr (float): Final learning rate of warm up. begin(int, optional): The begin step. The initial value of global_step described above. The default value is 0. step(int, optional): The step size used to calculate the new global_step in the description above. The default value is 1. dtype(str, optional): The data type used to create the learning rate variable. The data type can be set as 'float32', 'float64'. The default value is 'float32'. Returns: Variable: Warm-up learning rate with the same data type as learning_rate. Examples: .. code-block:: python import paddle.fluid as fluid learning_rate = 0.1 warmup_steps = 50 start_lr = 1. / 3. end_lr = 0.1 with fluid.dygraph.guard(): lr_decay = fluid.dygraph.LinearLrWarmup( learning_rate, warmup_steps, start_lr, end_lr) """ def __init__(self, learning_rate, warmup_steps, start_lr, end_lr, begin=1, step=1, dtype='float32'): super(LinearLrWarmup, self).__init__(begin, step, dtype) type_check = isinstance(learning_rate, float) or isinstance( learning_rate, int) or isinstance(learning_rate, LearningRateDecay) if not type_check: raise TypeError( "the type of learning_rate should be [int, float or LearningRateDecay], the current type is {}". format(learning_rate)) self.learning_rate = learning_rate self.warmup_steps = warmup_steps assert end_lr > start_lr, "end_lr {} must be greater than start_lr {}".format( end_lr, start_lr) self.lr_ratio_before_warmup = ( float(end_lr) - float(start_lr)) / float(warmup_steps) def step(self): base_lr = self.learning_rate if isinstance(self.learning_rate, LearningRateDecay): base_lr = base_lr() from .. import layers if self.step_num < self.warmup_steps: return self.lr_ratio_before_warmup * self.step_num else: return base_lr