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# Copyright 2021 Huawei Technologies Co., Ltd |
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# |
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# Licensed under the Apache License, Version 2.0 (the "License"); |
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# you may not use this file except in compliance with the License. |
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# You may obtain a copy of the License at |
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# |
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# http://www.apache.org/licenses/LICENSE-2.0 |
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# |
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# Unless required by applicable law or agreed to in writing, software |
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# distributed under the License is distributed on an "AS IS" BASIS, |
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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# See the License for the specific language governing permissions and |
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# limitations under the License. |
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# ============================================================================ |
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"""momentum""" |
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from mindspore.ops import functional as F, composite as C, operations as P |
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from mindspore.common.parameter import Parameter |
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from mindspore.common.tensor import Tensor |
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import mindspore.common.dtype as mstype |
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from mindspore._checkparam import Validator |
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from mindspore.nn.optim.optimizer import Optimizer |
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_momentum_opt = C.MultitypeFuncGraph("momentum_opt") |
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@_momentum_opt.register("Function", "Tensor", "Tensor", "Tensor", "Tensor", "Tensor", "Tensor", "Tensor") |
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def _tensor_run_opt_ext(opt, weight_decay, scale, momentum, learning_rate, gradient, weight, moment): |
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"""Apply momentum optimizer to the weight parameter using Tensor.""" |
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success = F.depend(True, opt(weight_decay, scale, weight, moment, learning_rate, gradient, momentum)) |
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return success |
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class Momentum(Optimizer): |
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r""" |
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Implements the Momentum algorithm. |
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Refer to the paper on the importance of initialization and momentum in deep learning for more details. |
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.. math:: |
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v_{t} = v_{t-1} \ast u + gradients |
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If use_nesterov is True: |
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.. math:: |
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p_{t} = p_{t-1} - (grad \ast lr + v_{t} \ast u \ast lr) |
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If use_nesterov is Flase: |
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.. math:: |
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p_{t} = p_{t-1} - lr \ast v_{t} |
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Here: where grad, lr, p, v and u denote the gradients, learning_rate, params, moments, and momentum respectively. |
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Note: |
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When separating parameter groups, the weight decay in each group will be applied on the parameters if the |
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weight decay is positive. When not separating parameter groups, the `weight_decay` in the API will be applied |
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on the parameters without 'beta' or 'gamma' in their names if `weight_decay` is positive. |
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To improve parameter groups performance, the customized order of parameters can be supported. |
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Args: |
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params (Union[list[Parameter], list[dict]]): When the `params` is a list of `Parameter` which will be updated, |
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the element in `params` must be class `Parameter`. When the `params` is a list of `dict`, the "params", |
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"lr", "weight_decay" and "order_params" are the keys can be parsed. |
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- params: Required. The value must be a list of `Parameter`. |
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- lr: Optional. If "lr" in the keys, the value of corresponding learning rate will be used. |
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If not, the `learning_rate` in the API will be used. |
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- weight_decay: Optional. If "weight_decay" in the keys, the value of corresponding weight decay |
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will be used. If not, the `weight_decay` in the API will be used. |
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- order_params: Optional. If "order_params" in the keys, the value must be the order of parameters and |
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the order will be followed in optimizer. There are no other keys in the `dict` and the parameters which |
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in the value of 'order_params' must be in one of group parameters. |
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learning_rate (Union[float, Tensor, Iterable, LearningRateSchedule]): A value or a graph for the learning rate. |
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When the learning_rate is an Iterable or a Tensor in a 1D dimension, use dynamic learning rate, then |
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the i-th step will take the i-th value as the learning rate. When the learning_rate is LearningRateSchedule, |
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use dynamic learning rate, the i-th learning rate will be calculated during the process of training |
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according to the formula of LearningRateSchedule. When the learning_rate is a float or a Tensor in a zero |
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dimension, use fixed learning rate. Other cases are not supported. The float learning rate must be |
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equal to or greater than 0. If the type of `learning_rate` is int, it will be converted to float. |
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momentum (float): Hyperparameter of type float, means momentum for the moving average. |
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It must be at least 0.0. |
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weight_decay (int, float): Weight decay (L2 penalty). It must be equal to or greater than 0.0. Default: 0.0. |
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loss_scale (int, float): A floating point value for the loss scale. It must be greater than 0.0. Default: 1.0. |
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use_nesterov (bool): Enable Nesterov momentum. Default: False. |
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Inputs: |
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- **gradients** (tuple[Tensor]) - The gradients of `params`, the shape is the same as `params`. |
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Outputs: |
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tuple[bool], all elements are True. |
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Raises: |
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ValueError: If the momentum is less than 0.0. |
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TypeError: If the momentum is not a float or use_nesterov is not a bool. |
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Supported Platforms: |
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``GPU`` |
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Examples: |
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>>> net = Net() |
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>>> #1) All parameters use the same learning rate and weight decay |
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>>> optim = Momentum(params=net.trainable_params(), learning_rate=0.1, momentum=0.9) |
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>>> |
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>>> #2) Use parameter groups and set different values |
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>>> conv_params = list(filter(lambda x: 'conv' in x.name, net.trainable_params())) |
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>>> no_conv_params = list(filter(lambda x: 'conv' not in x.name, net.trainable_params())) |
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>>> group_params = [{'params': conv_params, 'weight_decay': 0.01}, |
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... {'params': no_conv_params, 'lr': 0.01}, |
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... {'order_params': net.trainable_params()}] |
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>>> optim = Momentum(group_params, learning_rate=0.1, momentum=0.9, weight_decay=0.0) |
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>>> # The conv_params's parameters will use a learning rate of default value 0.1 and a weight decay of 0.01. |
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>>> # The no_conv_params's parameters will use a learning rate of 0.01 and a weight decay of default value 0.0. |
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>>> # The final parameters order in which the optimizer will be followed is the value of 'order_params'. |
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>>> |
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>>> loss = nn.SoftmaxCrossEntropyWithLogits() |
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>>> model = Model(net, loss_fn=loss, optimizer=optim, metrics=None) |
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""" |
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def __init__(self, params, learning_rate, momentum, weight_decay=0.0, loss_scale=1.0, use_nesterov=False): |
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super(Momentum, self).__init__(learning_rate, params, weight_decay, loss_scale) |
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Validator.check_value_type("momentum", momentum, [float], self.cls_name) |
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if isinstance(momentum, float) and momentum < 0.0: |
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raise ValueError("momentum should be at least 0.0, but got momentum {}".format(momentum)) |
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self.momentum = Parameter(Tensor(momentum, mstype.float32), name="momentum") |
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self.params = self.parameters |
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self.use_nesterov = Validator.check_bool(use_nesterov) |
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self.moments = self.params.clone(prefix="moments", init='zeros') |
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self.hyper_map = C.HyperMap() |
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# Use FusedWeightScaleApplyMomentum to avoid extra kernel launch. |
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self.opt = P.FusedWeightScaleApplyMomentum() |
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def construct(self, gradients): |
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params = self.params |
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moments = self.moments |
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weight_decay = Tensor(0.0, mstype.float32) |
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scale = Tensor(1.0, mstype.float32) |
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if self.exec_weight_decay: |
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weight_decay = self.weight_decay_tensor |
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if self.need_scale: |
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scale = self.reciprocal_scale |
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lr = self.get_lr() |
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if self.is_group_lr: |
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success = self.hyper_map(F.partial(_momentum_opt, self.opt, weight_decay, scale, self.momentum), |
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lr, gradients, params, moments) |
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else: |
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success = self.hyper_map(F.partial(_momentum_opt, self.opt, weight_decay, scale, self.momentum, lr), |
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gradients, params, moments) |
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return success |