# Copyright 2020 Huawei Technologies Co., Ltd
#
# 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
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# ============================================================================
"""lars optimizer"""
from mindspore.ops import operations as P
from mindspore.ops import composite as C
from mindspore.ops import functional as F
from mindspore._checkparam import Validator as validator
from mindspore.common import Tensor, Parameter, dtype as mstype
from .optimizer import _grad_scale, Optimizer
from .optimizer import opt_init_args_register
_lars_opt = C.MultitypeFuncGraph("lars_opt")
@_lars_opt.register("Function", "Tensor", "Number", "Tensor", "Tensor", "Bool", "Bool")
def _tensor_run_opt(lars, learning_rate, weight_decay, gradient, weight, decay_flag, lars_flag):
"""Apply lars optimizer to the weight parameter."""
if lars_flag:
op_reduce_sum = P.SquareSumAll()
w_square_sum, grad_square_sum = op_reduce_sum(weight, gradient)
if decay_flag:
grad_t = lars(weight, gradient, w_square_sum, grad_square_sum, weight_decay, learning_rate)
else:
num_zero = 0.0
grad_t = lars(weight, gradient, w_square_sum, grad_square_sum, num_zero, learning_rate)
return grad_t
return gradient
def _check_param_value(optimizer, epsilon, coefficient, use_clip, prim_name):
validator.check_value_type("optimizer", optimizer, Optimizer, prim_name)
validator.check_value_type("epsilon", epsilon, [float], prim_name)
validator.check_value_type("coefficient", coefficient, [float], prim_name)
validator.check_value_type("use_clip", use_clip, [bool], prim_name)
[docs]class LARS(Optimizer):
r"""
Implements the LARS algorithm with LARSUpdate Operator.
LARS is an optimization algorithm employing a large batch optimization technique. Refer to paper `LARGE BATCH
TRAINING OF CONVOLUTIONAL NETWORKS <https://arxiv.org/abs/1708.03888>`_.
The updating formulas are as follows,
.. math::
\begin{array}{ll} \\
\lambda = \frac{\theta \text{ * } || \omega || } \\
{|| g_{t} || \text{ + } \delta \text{ * } || \omega || } \\
\lambda =
\begin{cases}
\min(\frac{\lambda}{\alpha }, 1)
& \text{ if } clip = True \\
\lambda
& \text{ otherwise }
\end{cases}\\
g_{t+1} = \lambda * (g_{t} + \delta * \omega)
\end{array}
:math:`\theta` represents `coefficient`, :math:`\omega` represents `parameters`, :math:`g` represents `gradients`,
:math:`t` represents updating step, :math:`\delta` represents `weight_decay`,
:math:`\alpha` represents `learning_rate`, :math:`clip` represents `use_clip`.
Args:
optimizer (Optimizer): MindSpore optimizer for which to wrap and modify gradients.
epsilon (float): Term added to the denominator to improve numerical stability. Default: 1e-05.
coefficient (float): Trust coefficient for calculating the local learning rate. Default: 0.001.
use_clip (bool): Whether to use clip operation for calculating the local learning rate. Default: False.
lars_filter (Function): A function to determine whether apply the LARS algorithm. Default:
lambda x: 'LayerNorm' not in x.name and 'bias' not in x.name.
Inputs:
- **gradients** (tuple[Tensor]) - The gradients of `params` in the optimizer, the shape is the
as same as the `params` in the optimizer.
Outputs:
Union[Tensor[bool], tuple[Parameter]], it depends on the output of `optimizer`.
Supported Platforms:
``Ascend`` ``CPU``
Examples:
>>> net = Net()
>>> loss = nn.SoftmaxCrossEntropyWithLogits()
>>> opt = nn.Momentum(net.trainable_params(), 0.1, 0.9)
>>> opt_lars = nn.LARS(opt, epsilon=1e-08, coefficient=0.02)
>>> model = Model(net, loss_fn=loss, optimizer=opt_lars, metrics=None)
"""
@opt_init_args_register
def __init__(self, optimizer, epsilon=1e-05, coefficient=0.001, use_clip=False,
lars_filter=lambda x: 'LayerNorm' not in x.name and 'bias' not in x.name):
super(LARS, self).__init__(0.0, [Parameter(Tensor(0.0), name="fake_param")])
_check_param_value(optimizer, epsilon, coefficient, use_clip, self.cls_name)
self.opt = optimizer
self.parameters = optimizer.parameters
self.use_clip = use_clip
self.lars_flag = tuple(lars_filter(x) for x in self.parameters)
self.is_group = optimizer.is_group
self.learning_rate = Parameter(Tensor(0.0, dtype=mstype.float32), name="fake_lr")
self.decay_flags = optimizer.decay_flags
self.reciprocal_scale = optimizer.reciprocal_scale
self.need_scale = optimizer.need_scale
self.lars = P.LARSUpdate(epsilon, coefficient, use_clip)
self.cast = P.Cast()
if use_clip:
self.is_group_lr = optimizer.is_group_lr
self.dynamic_lr = optimizer.dynamic_lr
self.origin_learning_rate = optimizer.learning_rate
self.global_step = optimizer.global_step
if self.is_group_lr and self.dynamic_lr:
raise ValueError('Grouped dynamic learning rate is currently not supported for the inputs optimizer ' \
'of lars.')
if self.is_group:
self.weight_decay = tuple(map(lambda x: x / optimizer.loss_scale, optimizer.weight_decay))
optimizer.weight_decay = tuple(map(lambda x: 0.0, optimizer.weight_decay))
else:
self.weight_decay = optimizer.weight_decay / optimizer.loss_scale
optimizer.weight_decay = 0.0
optimizer.decay_flags = tuple(map(lambda x: False, self.decay_flags))
optimizer.reciprocal_scale = 1.0
optimizer.exec_weight_decay = False
def _get_lr(self):
"""Get the learning rate of current step."""
lr = self.origin_learning_rate
if self.dynamic_lr:
if self.is_group_lr:
lr = ()
for learning_rate in self.origin_learning_rate:
current_dynamic_lr = learning_rate(self.global_step)
lr += (current_dynamic_lr,)
else:
lr = self.origin_learning_rate(self.global_step)
return lr
def construct(self, gradients):
params = self.parameters
if self.use_clip:
lr = self._get_lr()
else:
lr = self.learning_rate
if self.need_scale:
gradients = self.hyper_map(F.partial(_grad_scale, self.reciprocal_scale), gradients)
if self.is_group:
if self.is_group_lr:
gradients = self.hyper_map(F.partial(_lars_opt, self.lars), lr, self.weight_decay,
gradients, params, self.decay_flags, self.lars_flag)
else:
gradients = self.hyper_map(F.partial(_lars_opt, self.lars, lr), self.weight_decay,
gradients, params, self.decay_flags, self.lars_flag)
else:
gradients = self.hyper_map(F.partial(_lars_opt, self.lars, lr, self.weight_decay),
gradients, params, self.decay_flags, self.lars_flag)
success = self.opt(gradients)
return success