# 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 # limitations under the License. import math import numpy import warnings from paddle import Tensor import paddle.fluid.core as core from ..fluid.framework import _in_legacy_dygraph __all__ = [ # noqa 'LRScheduler', 'NoamDecay', 'PiecewiseDecay', 'NaturalExpDecay', 'InverseTimeDecay', 'PolynomialDecay', 'LinearWarmup', 'ExponentialDecay', 'MultiStepDecay', 'StepDecay', 'LambdaDecay', 'ReduceOnPlateau', 'CosineAnnealingDecay', 'MultiplicativeDecay' ] class LRScheduler(object): """ LRScheduler Base class. Define the common interface of a learning rate scheduler. User can import it by ``from paddle.optimizer.lr import LRScheduler`` , then overload it for your subclass and have a custom implementation of ``get_lr()`` . Otherwise, an ``NotImplementedError`` exception will be thrown. Args: learning_rate (float): The initial learning rate. It is a python float number. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: instance to schedule learning rate. Examples: Here is an example of a simple ``StepDecay`` implementation. .. code-block:: python import paddle from paddle.optimizer.lr import LRScheduler class StepDecay(LRScheduler): def __init__(self, learning_rate, step_size, gamma=0.1, last_epoch=-1, verbose=False): if not isinstance(step_size, int): raise TypeError( "The type of 'step_size' must be 'int', but received %s." % type(step_size)) if gamma >= 1.0: raise ValueError('gamma should be < 1.0.') self.step_size = step_size self.gamma = gamma super(StepDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): i = self.last_epoch // self.step_size return self.base_lr * (self.gamma**i) """ def __init__(self, learning_rate=0.1, last_epoch=-1, verbose=False): if not isinstance(learning_rate, (float, int)): raise TypeError( "The type of learning rate must be float, but received {}". format(type(learning_rate))) self.base_lr = float(learning_rate) self.last_lr = float(learning_rate) self.last_epoch = last_epoch self.verbose = verbose self._var_name = None self.step() def __call__(self): """ Return lastest computed learning rate on current epoch. """ return self.last_lr def step(self, epoch=None): """ ``step`` should be called after ``optimizer.step`` . It will update the learning rate in optimizer according to current ``epoch`` . The new learning rate will take effect on next ``optimizer.step`` . Args: epoch (int, None): specify current epoch. Default: None. Auto-increment from last_epoch=-1. Returns: None """ if epoch is None: self.last_epoch += 1 self.last_lr = self.get_lr() else: self.last_epoch = epoch if hasattr(self, "_get_closed_form_lr"): self.last_lr = self._get_closed_form_lr() else: self.last_lr = self.get_lr() if self.verbose: print('Epoch {}: {} set learning rate to {}.'.format( self.last_epoch, self.__class__.__name__, self.last_lr)) def state_dict(self): """ Returns the state of the scheduler as a :class:`dict`. It is a subset of ``self.__dict__`` . """ self.state_keys() state_dict = {} for key in self.keys: if key not in self.__dict__: continue value = self.__dict__[key] if isinstance(value, Tensor): assert value.shape == [ 1 ], "shape of Tensor in state_dict must be [1] {}".format( value.shape) value = value.numpy()[0] state_dict[key] = value return state_dict # For those subclass who overload LRScheduler, "last_epoch, last_lr" will be saved by default. # (Note): you can change it for your subclass. def state_keys(self): """ For those subclass who overload ``LRScheduler`` (Base Class). Acquiescently, "last_epoch, last_lr" will be saved by ``self.keys = ['last_epoch', 'last_lr']`` . ``last_epoch`` is the current epoch num, and ``last_lr`` is the current learning rate. If you want to change the default behavior, you should have a custom implementation of ``_state_keys()`` to redefine ``self.keys`` . """ self.keys = ['last_epoch', 'last_lr'] def set_state_dict(self, state_dict): """ Loads the schedulers state. """ self.state_keys() for key in self.keys: if key in state_dict: self.__dict__[key] = state_dict[key] else: raise RuntimeError( "Please check whether state_dict is correct for optimizer. Can't find [ {} ] in state_dict". format(key)) if len(state_dict) > len(self.keys): warnings.warn( "There are some unused values in state_dict. Maybe the optimizer have different 'LearningRateDecay' when invoking state_dict and set_dict" ) # alias for set_state_dict set_dict = set_state_dict def get_lr(self): """ For those subclass who overload ``LRScheduler`` (Base Class), User should have a custom implementation of ``get_lr()`` . Otherwise, an ``NotImplementedError`` exception will be thrown. """ # calculate by python float raise NotImplementedError class NoamDecay(LRScheduler): r""" Applies Noam Decay to the initial learning rate. The algorithm can be described as following. .. math:: new\_learning\_rate = learning\_rate * d_{model}^{-0.5} * min(epoch^{-0.5}, epoch * warmup\_steps^{-1.5}) Please reference `attention is all you need `_ Args: d$_{model}$(int): The dimensionality of input and output feature vector of model. It is a python int number. warmup_steps(int): The number of warmup steps. A super parameter. It is a python int number learning_rate (float): The initial learning rate. It is a python float number. Default: 1.0. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``NoamDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.NoamDecay(d_model=0.01, warmup_steps=100, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.NoamDecay(d_model=0.01, warmup_steps=100, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, d_model, warmup_steps, learning_rate=1.0, last_epoch=-1, verbose=False): self.d_model = d_model self.warmup_steps = warmup_steps super(NoamDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): if self.last_epoch == 0: a = 1 else: a = self.last_epoch**-0.5 b = self.warmup_steps**-1.5 * self.last_epoch return self.base_lr * (self.d_model**-0.5) * min(a, b) class PiecewiseDecay(LRScheduler): """ Piecewise learning rate scheduler. The algorithm can be described as the code below: .. code-block:: text boundaries = [100, 200] values = [1.0, 0.5, 0.1] if epoch < 100: learning_rate = 1.0 elif 100 <= global_step < 200: learning_rate = 0.5 else: learning_rate = 0.1 Args: boundaries(list|tuple): A list/tuple of steps numbers. The type of element in the list is python int. values(list|tuple): A list/tuple of learning rate values that will be picked during different epoch boundaries. The type of element in the list is python float. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``PiecewiseDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.PiecewiseDecay(boundaries=[3, 6, 9], values=[0.1, 0.2, 0.3, 0.4], verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.PiecewiseDecay(boundaries=[3, 6, 9], values=[0.1, 0.2, 0.3, 0.4], verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, boundaries, values, last_epoch=-1, verbose=False): self.boundaries = boundaries self.values = values super(PiecewiseDecay, self).__init__( last_epoch=last_epoch, verbose=verbose) def get_lr(self): for i in range(len(self.boundaries)): if self.last_epoch < self.boundaries[i]: return self.values[i] return self.values[len(self.values) - 1] class NaturalExpDecay(LRScheduler): r""" Applies natural exponential decay to the initial learning rate. The algorithm can be described as following: .. math:: new\_learning\_rate = learning\_rate * e^{- gamma * epoch} Args: learning_rate (float): The initial learning rate. It is a python float number. gamma (float, optional): A Ratio to update the learning rate, should greater than 0.0 to make learning rate decay. Default: 0.1. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``NaturalExpDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.NaturalExpDecay(learning_rate=0.5, gamma=0.1, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.NaturalExpDecay(learning_rate=0.5, gamma=0.1, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, gamma, last_epoch=-1, verbose=False): assert gamma > 0.0, " 'gamma' must be a positive number so that the learning rate will decay." self.gamma = gamma super(NaturalExpDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): return self.base_lr * math.exp(-1 * self.gamma * self.last_epoch) class InverseTimeDecay(LRScheduler): r""" Applies inverse time decay to the initial learning rate. The algorithm can be described as following: .. math:: new\_learning\_rate = \frac{learning\_rate}{1 + gamma * epoch} Args: learning_rate (float): The initial learning rate. It is a python float number. gamma (float, optional): The Ratio that the learning rate will be reduced. ``new_lr = origin_lr * gamma`` . It should be less than 1.0. Default: 0.1. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``InverseTimeDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.InverseTimeDecay(learning_rate=0.5, gamma=0.1, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.InverseTimeDecay(learning_rate=0.5, gamma=0.1, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, gamma, last_epoch=-1, verbose=False): self.gamma = gamma super(InverseTimeDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): return self.base_lr / (1 + self.gamma * self.last_epoch) class PolynomialDecay(LRScheduler): r""" 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{epoch}{decay\_steps}) new\_learning\_rate & = (learning\_rate-end\_lr)*(1-\frac{epoch}{decay\_steps})^{power}+end\_lr If cycle is set to False, then: .. math:: epoch & = min(epoch, decay\_steps) new\_learning\_rate & = (learning\_rate-end\_lr)*(1-\frac{epoch}{decay\_steps})^{power}+end\_lr Args: learning_rate (float): The initial learning rate. It is a python float number. decay_steps(int): The decay step size. It determines the decay cycle. It must be a positive integer. end_lr(float, optional): The minimum final learning rate. Default: 0.0001. power(float, optional): Power of polynomial, should greater than 0.0 to get learning rate decay. Default: 1.0. cycle(bool, optional): Whether the learning rate rises again. If True, then the learning rate will rise when it decrease to ``end_lr`` . If False, the learning rate is monotone decreasing. Default: False. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``PolynomialDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.PolynomialDecay(learning_rate=0.5, decay_steps=20, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.PolynomialDecay(learning_rate=0.5, decay_steps=20, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, decay_steps, end_lr=0.0001, power=1.0, cycle=False, last_epoch=-1, verbose=False): assert decay_steps > 0 and isinstance( decay_steps, int), " 'decay_steps' must be a positive integer." self.decay_steps = decay_steps self.end_lr = end_lr assert power > 0.0, " 'power' must be greater than 0.0 so that the learning rate will decay." self.power = power self.cycle = cycle super(PolynomialDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): tmp_epoch_num = self.last_epoch tmp_decay_steps = self.decay_steps if self.cycle: div_res = math.ceil( float(self.last_epoch) / float(self.decay_steps)) if self.last_epoch == 0: div_res = 1 tmp_decay_steps = self.decay_steps * div_res else: tmp_epoch_num = min(self.last_epoch, self.decay_steps) return (self.base_lr - self.end_lr) * ( (1 - float(tmp_epoch_num) / float(tmp_decay_steps) )**self.power) + self.end_lr class LinearWarmup(LRScheduler): r""" Linear learning rate warm up strategy. Update the learning rate preliminarily before the normal learning rate scheduler. For more information, please refer to `Bag of Tricks for Image Classification with Convolutional Neural Networks `_ When epoch < warmup_steps, learning rate is updated as: .. math:: lr = start\_lr + (end\_lr - start\_lr) * \frac{epoch}{warmup\_steps} where start_lr is the initial learning rate, and end_lr is the final learning rate; When epoch >= warmup_steps, learning rate is updated as: .. math:: lr = learning_rate where ``learning_rate`` is float or any subclass of ``LRScheduler`` . Args: learning_rate (float|LRScheduler): The learning rate after warm-up. It is a python float number or any subclass of ``LRScheduler`` . warmup_steps (int): total steps of warm up. It must be a positive integer. start_lr (float): Initial learning rate of warm up. end_lr (float): Final learning rate of warm up. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``LinearWarmup`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.LinearWarmup( learning_rate=0.5, warmup_steps=20, start_lr=0, end_lr=0.5, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.LinearWarmup( learning_rate=0.5, warmup_steps=20, start_lr=0, end_lr=0.5, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, warmup_steps, start_lr, end_lr, last_epoch=-1, verbose=False): type_check = isinstance(learning_rate, float) or isinstance( learning_rate, int) or isinstance(learning_rate, LRScheduler) if not type_check: raise TypeError( "the type of learning_rate should be [int, float or LRScheduler], the current type is {}". format(learning_rate)) self.learning_rate = learning_rate assert warmup_steps > 0 and isinstance( warmup_steps, int), " 'warmup_steps' must be a positive integer." self.warmup_steps = warmup_steps self.start_lr = start_lr self.end_lr = end_lr assert end_lr > start_lr, "end_lr {} must be greater than start_lr {}".format( end_lr, start_lr) super(LinearWarmup, self).__init__(start_lr, last_epoch, verbose) def state_dict(self): """ Returns the state of the LinearWarmup scheduler as a :class:`dict`. It is a subset of ``self.__dict__`` . """ state_dict = super(LinearWarmup, self).state_dict() if isinstance(self.learning_rate, LRScheduler): state_dict["LinearWarmup_LR"] = self.learning_rate.state_dict() return state_dict def set_state_dict(self, state_dict): """ Loads state_dict for LinearWarmup scheduler. """ super(LinearWarmup, self).set_state_dict(state_dict) if isinstance(self.learning_rate, LRScheduler): self.learning_rate.set_state_dict(state_dict["LinearWarmup_LR"]) def get_lr(self): if self.last_epoch < self.warmup_steps: return (self.end_lr - self.start_lr) * float( self.last_epoch) / float(self.warmup_steps) + self.start_lr else: if isinstance(self.learning_rate, LRScheduler): self.learning_rate.step(self.last_epoch - self.warmup_steps) return self.learning_rate() return self.learning_rate class ExponentialDecay(LRScheduler): r""" Update learning rate by `gamma` each epoch. The algorithm can be described as following. .. math:: new\_learning\_rate = last\_learning\_rate * gamma Args: learning_rate (float): The initial learning rate. It is a python float number. gamma (float): The Ratio that the learning rate will be reduced. ``new_lr = origin_lr * gamma`` . It should be in interval (0.0, 1.0). last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``ExponentialDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.ExponentialDecay(learning_rate=0.5, gamma=0.9, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.ExponentialDecay(learning_rate=0.5, gamma=0.9, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, gamma, last_epoch=-1, verbose=False): assert gamma > 0.0 and gamma < 1.0, " 'gamma' must be in interval (0.0, 1.0) so that the learning rate will decay." self.gamma = gamma super(ExponentialDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): return self.base_lr * (self.gamma**self.last_epoch) class MultiStepDecay(LRScheduler): """ Update the learning rate by ``gamma`` once ``epoch`` reaches one of the milestones. The algorithm can be described as the code below. .. code-block:: text learning_rate = 0.5 milestones = [30, 50] gamma = 0.1 if epoch < 30: learning_rate = 0.5 elif epoch < 50: learning_rate = 0.05 else: learning_rate = 0.005 Args: learning_rate (float): The initial learning rate. It is a python float number. milestones (tuple|list): List or tuple of each boundaries. Must be increasing. gamma (float, optional): The Ratio that the learning rate will be reduced. ``new_lr = origin_lr * gamma`` . It should be less than 1.0. Default: 0.1. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``MultiStepDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.MultiStepDecay(learning_rate=0.5, milestones=[2, 4, 6], gamma=0.8, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.MultiStepDecay(learning_rate=0.5, milestones=[2, 4, 6], gamma=0.8, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, milestones, gamma=0.1, last_epoch=-1, verbose=False): if not isinstance(milestones, (tuple, list)): raise TypeError( "The type of 'milestones' in 'MultiStepDecay' must be 'tuple, list', but received %s." % type(milestones)) if not all([ milestones[i] < milestones[i + 1] for i in range(len(milestones) - 1) ]): raise ValueError('The elements of milestones must be incremented') if gamma >= 1.0: raise ValueError('gamma should be < 1.0.') self.milestones = milestones self.gamma = gamma super(MultiStepDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): for i in range(len(self.milestones)): if self.last_epoch < self.milestones[i]: return self.base_lr * (self.gamma**i) return self.base_lr * (self.gamma**len(self.milestones)) class StepDecay(LRScheduler): """ Update the learning rate of ``optimizer`` by ``gamma`` every ``step_size`` number of epoch. The algorithm can be described as the code below. .. code-block:: text learning_rate = 0.5 step_size = 30 gamma = 0.1 learning_rate = 0.5 if epoch < 30 learning_rate = 0.05 if 30 <= epoch < 60 learning_rate = 0.005 if 60 <= epoch < 90 ... Args: learning_rate (float): The initial learning rate. It is a python float number. step_size (int): the interval to update. It must be a positive integer. gamma (float, optional): The Ratio that the learning rate will be reduced. ``new_lr = origin_lr * gamma`` . It should be less than 1.0. Default: 0.1. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``StepDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.StepDecay(learning_rate=0.5, step_size=5, gamma=0.8, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.StepDecay(learning_rate=0.5, step_size=5, gamma=0.8, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, step_size, gamma=0.1, last_epoch=-1, verbose=False): if not isinstance(step_size, int): raise TypeError( "The type of 'step_size' must be 'int', but received %s." % type(step_size)) if gamma >= 1.0: raise ValueError('gamma should be < 1.0.') assert step_size > 0 and isinstance( step_size, int), " 'step_size' must be a positive integer." self.step_size = step_size self.gamma = gamma super(StepDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): i = self.last_epoch // self.step_size return self.base_lr * (self.gamma**i) class LambdaDecay(LRScheduler): """ Sets the learning rate of ``optimizer`` by function ``lr_lambda`` . ``lr_lambda`` is funciton which receives ``epoch`` . The algorithm can be described as the code below. .. code-block:: text learning_rate = 0.5 # init learning_rate lr_lambda = lambda epoch: 0.95 ** epoch learning_rate = 0.5 # epoch 0, 0.5*0.95**0 learning_rate = 0.475 # epoch 1, 0.5*0.95**1 learning_rate = 0.45125 # epoch 2, 0.5*0.95**2 Args: learning_rate (float): The initial learning rate. It is a python float number. lr_lambda (function): A function which computes a factor by ``epoch`` , and then multiply the initial learning rate by this factor. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``LambdaDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.LambdaDecay(learning_rate=0.5, lr_lambda=lambda x:0.95**x, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.LambdaDecay(learning_rate=0.5, lr_lambda=lambda x:0.95**x, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, lr_lambda, last_epoch=-1, verbose=False): if not callable(lr_lambda): raise TypeError( "The type of 'lr_lambda' in 'LambdaDecay' must be 'function', but received %s." % type(lr_lambda)) self.lr_lambda = lr_lambda super(LambdaDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): return self.base_lr * self.lr_lambda(self.last_epoch) class ReduceOnPlateau(LRScheduler): """ Reduce learning rate when ``metrics`` has stopped descending. Models often benefit from reducing the learning rate by 2 to 10 times once model performance has no longer improvement. The ``metrics`` is the one which has been pass into ``step`` , it must be 1-D Tensor with shape [1]. When ``metrics`` stop descending for a ``patience`` number of epochs, the learning rate will be reduced to ``learning_rate * factor`` . (Specially, ``mode`` can also be set to ``'max`` , in this case, when ``metrics`` stop ascending for a ``patience`` number of epochs, the learning rate will be reduced.) In addition, After each reduction, it will wait a ``cooldown`` number of epochs before resuming above operation. Args: learning_rate (float): The initial learning rate. It is a python float number. mode (str, optional): ``'min'`` or ``'max'`` can be selected. Normally, it is ``'min'`` , which means that the learning rate will reduce when ``loss`` stops descending. Specially, if it's set to ``'max'`` , the learning rate will reduce when ``loss`` stops ascending. Default: ``'min'`` . factor (float, optional): The Ratio that the learning rate will be reduced. ``new_lr = origin_lr * factor`` . It should be less than 1.0. Default: 0.1. patience (int, optional): When ``loss`` doesn't improve for this number of epochs, learing rate will be reduced. Default: 10. threshold (float, optional): ``threshold`` and ``threshold_mode`` will determine the minimum change of ``loss`` . This make tiny changes of ``loss`` will be ignored. Default: 1e-4. threshold_mode (str, optional): ``'rel'`` or ``'abs'`` can be selected. In ``'rel'`` mode, the minimum change of ``loss`` is ``last_loss * threshold`` , where ``last_loss`` is ``loss`` in last epoch. In ``'abs'`` mode, the minimum change of ``loss`` is ``threshold`` . Default: ``'rel'`` . cooldown (int, optional): The number of epochs to wait before resuming normal operation. Default: 0. min_lr (float, optional): The lower bound of the learning rate after reduction. Default: 0. epsilon (float, optional): Minimal decay applied to lr. If the difference between new and old lr is smaller than epsilon, the update is ignored. Default: 1e-8. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False``. Returns: ``ReduceOnPlateau`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.ReduceOnPlateau(learning_rate=1.0, factor=0.5, patience=5, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step(loss) # If you update learning rate each step # scheduler.step(loss) # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.ReduceOnPlateau(learning_rate=1.0, factor=0.5, patience=5, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step(out[0]) # If you update learning rate each step # scheduler.step(out[0]) # If you update learning rate each epoch """ def __init__(self, learning_rate, mode='min', factor=0.1, patience=10, threshold=1e-4, threshold_mode='rel', cooldown=0, min_lr=0, epsilon=1e-8, verbose=False): mode = mode.lower() if mode not in ['min', 'max']: raise ValueError('mode: ' + mode + ' is unknown!') self.mode = mode if factor >= 1.0: raise ValueError( 'new_lr = origin_lr * gamma and gamma should be < 1.0.') self.factor = factor threshold_mode = threshold_mode.lower() if threshold_mode not in ['rel', 'abs']: raise ValueError('threshold mode: ' + threshold_mode + ' is unknown!') self.threshold_mode = threshold_mode if not isinstance(learning_rate, (float, int)): raise TypeError( "The type of 'learning_rate' in 'ReduceOnPlateau' must be 'float', but received %s." % type(learning_rate)) self.patience = patience self.threshold = threshold self.threshold_mode = threshold_mode self.cooldown = cooldown self.min_lr = min_lr self.epsilon = epsilon self.cooldown_counter = 0 self.best = None self.num_bad_epochs = 0 # Can not call Parent __init__, so implement here. self.base_lr = float(learning_rate) self.last_lr = float(learning_rate) self.last_epoch = 0 self.verbose = verbose self._var_name = None # "cooldown_counter / best / num_bad_epochs / last_epoch / last_lr" will be stored. def state_keys(self): self.keys = [ 'cooldown_counter', 'best', 'num_bad_epochs', 'last_epoch', 'last_lr' ] def step(self, metrics, epoch=None): """ step should be called after `optimizer.step()` . It will update the learning rate in optimizer according to ``metrics`` . The new learning rate will take effect on next epoch. Args: metrics (Tensor|numpy.ndarray|float): Which will be monitored to determine whether the learning rate will reduce. If it stop descending for a ``patience`` number of epochs, the learning rate will reduce. If it's 'Tensor' or 'numpy.ndarray', its shape must be [1]. epoch (int, None): specify current epoch. Default: None. Auto-increment from last_epoch=-1. Returns: None Examples: Please refer to the example of current LRScheduler. """ if epoch is None: self.last_epoch = self.last_epoch + 1 else: self.last_epoch = epoch if not _in_legacy_dygraph(): tmp = core.eager.Tensor else: tmp = Tensor # loss must be float, numpy.ndarray or 1-D Tensor with shape [1] if isinstance(metrics, (tmp, numpy.ndarray)): assert len(metrics.shape) == 1 and metrics.shape[0] == 1, "the metrics.shape " \ "should be (1L,), but the current metrics.shape is {}. Maybe that " \ "you should call paddle.mean to process it first.".format( metrics.shape) elif not isinstance(metrics, (int, float, numpy.float32, numpy.float64)): raise TypeError( "metrics must be 'int', 'float', 'np.float', 'numpy.ndarray' or 'paddle.Tensor', but receive {}". format(type(metrics))) if self.cooldown_counter > 0: self.cooldown_counter -= 1 else: if self.best is None or self._is_better(metrics, self.best): self.best = metrics self.num_bad_epochs = 0 else: self.num_bad_epochs += 1 if self.num_bad_epochs > self.patience: self.cooldown_counter = self.cooldown self.num_bad_epochs = 0 new_lr = max(self.last_lr * self.factor, self.min_lr) if self.last_lr - new_lr > self.epsilon: self.last_lr = new_lr if self.verbose: print('Epoch {}: {} set learning rate to {}.'.format( self.last_epoch, self.__class__.__name__, self.last_lr)) def _is_better(self, current, best): if self.mode == 'min' and self.threshold_mode == 'rel': return current < best - best * self.threshold elif self.mode == 'min' and self.threshold_mode == 'abs': return current < best - self.threshold elif self.mode == 'max' and self.threshold_mode == 'rel': return current > best + best * self.threshold else: return current > best + self.threshold class CosineAnnealingDecay(LRScheduler): r""" Set the learning rate using a cosine annealing schedule, where :math:`\eta_{max}` is set to the initial learning_rate. :math:`T_{cur}` is the number of epochs since the last restart in SGDR. The algorithm can be described as following. .. math:: \eta_t & = \eta_{min} + \frac{1}{2}(\eta_{max} - \eta_{min})\left(1 + \cos\left(\frac{T_{cur}}{T_{max}}\pi\right)\right), & T_{cur} \neq (2k+1)T_{max}; \eta_{t+1} & = \eta_{t} + \frac{1}{2}(\eta_{max} - \eta_{min}) \left(1 - \cos\left(\frac{1}{T_{max}}\pi\right)\right), & T_{cur} = (2k+1)T_{max}. It has been proposed in `SGDR: Stochastic Gradient Descent with Warm Restarts `_. Note that this only implements the cosine annealing part of SGDR, and not the restarts. Args: learning_rate (float): The initial learning rate, that is :math:`\eta_{max}` . It can be set to python float or int number. T_max (int): Maximum number of iterations. It is half of the decay cycle of learning rate. It must be a positive integer. eta_min (float|int, optional): Minimum learning rate, that is :math:`\eta_{min}` . Default: 0. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``CosineAnnealingDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.CosineAnnealingDecay(learning_rate=0.5, T_max=10, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 4, 5]) y = paddle.static.data(name='y', shape=[None, 4, 5]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.CosineAnnealingDecay(learning_rate=0.5, T_max=10, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler) sgd.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for epoch in range(20): for batch_id in range(5): out = exe.run( main_prog, feed={ 'x': np.random.randn(3, 4, 5).astype('float32'), 'y': np.random.randn(3, 4, 5).astype('float32') }, fetch_list=loss.name) scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, T_max, eta_min=0, last_epoch=-1, verbose=False): if not isinstance(T_max, int): raise TypeError( "The type of 'T_max' in 'CosineAnnealingDecay' must be 'int', but received %s." % type(T_max)) if not isinstance(eta_min, (float, int)): raise TypeError( "The type of 'eta_min' in 'CosineAnnealingDecay' must be 'float, int', but received %s." % type(eta_min)) assert T_max > 0 and isinstance( T_max, int), " 'T_max' must be a positive integer." self.T_max = T_max self.eta_min = float(eta_min) super(CosineAnnealingDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): if self.last_epoch == 0: return self.base_lr elif (self.last_epoch - 1 - self.T_max) % (2 * self.T_max) == 0: return self.last_lr + (self.base_lr - self.eta_min) * (1 - math.cos( math.pi / self.T_max)) / 2 return (1 + math.cos(math.pi * self.last_epoch / self.T_max)) / ( 1 + math.cos(math.pi * (self.last_epoch - 1) / self.T_max)) * ( self.last_lr - self.eta_min) + self.eta_min def _get_closed_form_lr(self): return self.eta_min + (self.base_lr - self.eta_min) * (1 + math.cos( math.pi * self.last_epoch / self.T_max)) / 2 class MultiplicativeDecay(LRScheduler): """ Multiply the learning rate of ``optimizer`` by the factor given in function ``lr_lambda`` . The algorithm can be described as the code below. .. code-block:: text learning_rate = 0.5 # init learning_rate lr_lambda = lambda epoch: 0.95 learning_rate = 0.5 # epoch 0, learning_rate = 0.475 # epoch 1, 0.5*0.95 learning_rate = 0.45125 # epoch 2, 0.475*0.95 Args: learning_rate (float): The initial learning rate. It is a python float number. lr_lambda (function): A function which computes a factor by ``epoch`` , and then multiply the last learning rate by this factor. last_epoch (int, optional): The index of last epoch. Can be set to restart training. Default: -1, means initial learning rate. verbose (bool, optional): If ``True``, prints a message to stdout for each update. Default: ``False`` . Returns: ``MultiplicativeDecay`` instance to schedule learning rate. Examples: .. code-block:: python import paddle import numpy as np # train on default dynamic graph mode linear = paddle.nn.Linear(10, 10) scheduler = paddle.optimizer.lr.MultiplicativeDecay(learning_rate=0.5, lr_lambda=lambda x:0.95, verbose=True) sgd = paddle.optimizer.SGD(learning_rate=scheduler, parameters=linear.parameters()) for epoch in range(20): for batch_id in range(5): x = paddle.uniform([10, 10]) out = linear(x) loss = paddle.mean(out) loss.backward() sgd.step() sgd.clear_gradients() scheduler.step() # If you update learning rate each step # scheduler.step() # If you update learning rate each epoch """ def __init__(self, learning_rate, lr_lambda, last_epoch=-1, verbose=False): if not callable(lr_lambda): raise TypeError( "The type of 'lr_lambda' in 'MultiplicativeDecay' must be 'function', but received %s." % type(lr_lambda)) self.lr_lambda = lr_lambda super(MultiplicativeDecay, self).__init__(learning_rate, last_epoch, verbose) def get_lr(self): if self.last_epoch > 0: return self.last_lr * self.lr_lambda(self.last_epoch) else: return self.base_lr