# 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
# 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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# ============================================================================
"""sgd"""
from mindspore.ops import functional as F, composite as C, operations as P
from mindspore.common.parameter import Parameter
from mindspore.common.tensor import Tensor
import mindspore.common.dtype as mstype
from mindspore._checkparam import Validator as validator
from .optimizer import Optimizer
sgd_opt = C.MultitypeFuncGraph("sgd_opt")
@sgd_opt.register("Function", "Tensor", "Tensor", "Tensor", "Tensor", "Tensor", "Tensor")
def _tensor_run_opt_ext(opt, momentum, learning_rate, gradient, weight, accum, stat):
"""Apply sgd optimizer to the weight parameter using Tensor."""
success = True
success = F.depend(success, opt(weight, gradient, learning_rate, accum, momentum, stat))
return success
[docs]class SGD(Optimizer):
"""
Implements stochastic gradient descent (optionally with momentum).
Introduction to SGD can be found at https://en.wikipedia.org/wiki/Stochastic_gradient_descent.
Nesterov momentum is based on the formula from paper `On the importance of initialization and
momentum in deep learning <http://proceedings.mlr.press/v28/sutskever13.html>`_.
Note:
The SGD optimizer supports separating parameter groups. Different parameter groups can set different
`learning_rate` and `weight_decay`.
When separating parameter groups, the weight decay in each group will be applied on the parameters if the
value of weight_decay > 0. When not separating parameter groups, the `weight_decay` in the API will be
applied on the parameters if `weight_decay` > 0 and the 'beta' and 'gamma' are not in the name of parameters.
Args:
params (Union[list[Parameter], list[dict]]): When the `params` is a list of `Parameter` which will be updated,
the element in `params` should be class `Parameter`. When the `params` is a list of `dict`, the "params",
"lr" and "weight_decay" are the keys can be parsed.
- params: Required. The value should be a list of `Parameter`.
- lr: Optional. If "lr" in the keys, the value of corresponding learning rate will be used.
If not, the `learning_rate` in the API will be used.
- weight_decay: Optional. If "weight_decay" in the keys, the value of corresponding weight decay
will be used. If not, the `weight_decay` in the API will be used.
learning_rate (Union[float, Tensor, Iterable]): A value for the learning rate. When the learning_rate is
Iterable or a Tensor and the dims of the Tensor is 1,
use dynamic learning rate, then the i-th step will
take the i-th value as the learning rate.
When the learning_rate is float or learning_rate is a Tensor
but the dims of the Tensor is 0, use fixed learning rate.
Other cases are not supported. Default: 0.1.
momentum (float): A floating point value the momentum. Default: 0.0.
dampening (float): A floating point value of dampening for momentum. Default: 0.0.
weight_decay (float): Weight decay (L2 penalty). Default: 0.0.
nesterov (bool): Enables the Nesterov momentum. Default: False.
loss_scale (float): A floating point value for the loss scale, which should be larger
than 0.0. Default: 1.0.
Inputs:
- **gradients** (tuple[Tensor]) - The gradients of `params`, the shape is the same as `params`.
Outputs:
Tensor[bool], the value is True.
Raises:
ValueError: If the momentum, dampening or weight_decay value is less than 0.0.
Examples:
>>> net = Net()
>>> #1) All parameters use the same learning rate and weight decay
>>> optim = nn.SGD(params=net.trainable_params())
>>>
>>> #2) Use parameter groups and set different values
>>> conv_params = list(filter(lambda x: 'conv' in x.name, net.trainable_params()))
>>> no_conv_params = list(filter(lambda x: 'conv' not in x.name, net.trainable_params()))
>>> group_params = [{'params': conv_params, 'weight_decay': 0.01, 'lr': 0.01},
>>> {'params': no_conv_params}]
>>> opt = nn.SGD(group_params, learning_rate=0.1, weight_decay=0.0)
>>> # the conv_params's parameters will use a learning rate of 0.01 and a weight decay of 0.01
>>> # the no_cov_params's parameters don't set learning and weight decay. So they will use a
>>> # learning rate of 0.1 and a weight decay of 0.0.
>>>
>>> loss = nn.SoftmaxCrossEntropyWithLogits()
>>> model = Model(net, loss_fn=loss, optimizer=optim)
"""
def __init__(self, params, learning_rate=0.1, momentum=0.0, dampening=0.0, weight_decay=0.0, nesterov=False,
loss_scale=1.0):
super(SGD, self).__init__(learning_rate, params, weight_decay, loss_scale)
if not isinstance(momentum, float):
raise TypeError("momentum should be float number!")
if isinstance(momentum, float) and momentum < 0.0:
raise ValueError("momentum should be at least 0.0, but got momentum {}".format(momentum))
if not isinstance(dampening, float):
raise TypeError("dampening should be float number")
if isinstance(dampening, int):
dampening = float(dampening)
if dampening < 0.0:
raise ValueError("dampening should be at least 0.0, but got dampening {}".format(dampening))
self.dampening = dampening
validator.check_value_type("nesterov", nesterov, [bool], self.cls_name)
self.nesterov = nesterov
self.opt = P.SGD(dampening, weight_decay, nesterov)
self.momentum = Parameter(Tensor(momentum, mstype.float32), name="momentum")
self.accum = self.parameters.clone(prefix="accum", init='zeros')
self.stat = self.parameters.clone(prefix="stat", init='ones')
self.hyper_map = C.HyperMap()
def construct(self, gradients):
params = self.parameters
accum = self.accum
stat = self.stat
gradients = self.scale_grad(gradients)
lr = self.get_lr()
if self.is_group_lr:
success = self.hyper_map(F.partial(sgd_opt, self.opt, self.momentum), lr, gradients, params, accum, stat)
else:
success = self.hyper_map(F.partial(sgd_opt, self.opt, self.momentum, lr), gradients, params, accum, stat)
return success