Source code for mindspore.experimental.optim.nadam

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"""nadam"""
from __future__ import absolute_import

from mindspore.ops import functional as F, composite as C, operations as P
from mindspore.common import Parameter, Tensor
import mindspore.common.dtype as mstype
from mindspore import _checkparam as validator
from mindspore.experimental.optim.optimizer import Optimizer, check_not_less_than, check_not_less_than_without_equal
from mindspore import jit

_nadam_opt = C.MultitypeFuncGraph("nadam_opt")

op_sqrt = P.Sqrt()


@_nadam_opt.register("Number", "Number", "Number", "Number", "Tensor", "Tensor", "Tensor",
                     "Tensor", "Tensor", "Tensor", "Tensor")
def _tensor_run_opt(beta1, beta2, momentum_decay, eps, step_t, lr, param, grad, exp_avg, exp_avg_sq, mu_product):
    """Apply nadam optimizer to the weight parameter."""
    bias_correction2 = 1 - beta2 ** step_t
    mu = beta1 * (1. - 0.5 * (0.96 ** (step_t * momentum_decay)))
    mu_next = beta1 * (1. - 0.5 * (0.96 ** ((step_t + 1) * momentum_decay)))
    F.assign(mu_product, mu_product * mu)
    F.assign(exp_avg, exp_avg * beta1 + grad * (1 - beta1))
    F.assign(exp_avg_sq, exp_avg_sq * beta2 + grad * grad * (1 - beta2))

    denom = op_sqrt(exp_avg_sq / bias_correction2) + eps

    mu_product_next = mu_product * mu_next
    F.assign(param, param - lr * (1. - mu) / (1. - mu_product) * grad / denom)
    F.assign(param, param - (lr * mu_next) / (1. - mu_product_next) * exp_avg / denom)

    return True


[docs]class NAdam(Optimizer): r""" Implements NAdam algorithm. .. _Incorporating Nesterov Momentum into Adam: https://openreview.net/forum?id=OM0jvwB8jIp57ZJjtNEZ .. warning:: This is an experimental optimizer API that is subject to change. This module must be used with lr scheduler module in `LRScheduler Class <https://www.mindspore.cn/docs/en/r2.3.0rc1/api_python/mindspore.experimental.html#lrscheduler-class>`_ . Args: params (Union[list(Parameter), list(dict)]): list of parameters to optimize or dicts defining parameter groups. lr (Union[int, float, Tensor], optional): learning rate. Default: ``2e-3``. betas (Tuple[float, float], optional): coefficients used for computing running averages of gradient and its square. Default: ``(0.9, 0.999)``. eps (float, optional): term added to the denominator to improve numerical stability. Default: ``1e-8``. weight_decay (float, optional): weight decay (L2 penalty). Default: ``0.``. momentum_decay (float, optional): momentum momentum_decay. Default: ``4e-3``. Inputs: - **gradients** (tuple[Tensor]) - The gradients of `params`. Raises: ValueError: If the learning rate is not int, float or Tensor. ValueError: If the learning rate is less than 0. ValueError: If the `eps` is less than 0.0. ValueError: If the `weight_decay` is less than 0. ValueError: If the `momentum_decay` is less than 0. ValueError: If elements of `betas` not in the range of [0, 1). Supported Platforms: ``Ascend`` ``GPU`` ``CPU`` Examples: >>> import mindspore >>> from mindspore import nn >>> from mindspore.experimental import optim >>> # Define the network structure of LeNet5. Refer to >>> # https://gitee.com/mindspore/docs/blob/r2.3.q1/docs/mindspore/code/lenet.py >>> net = LeNet5() >>> loss_fn = nn.SoftmaxCrossEntropyWithLogits(sparse=True) >>> optimizer = optim.NAdam(net.trainable_params(), lr=0.1) >>> def forward_fn(data, label): ... logits = net(data) ... loss = loss_fn(logits, label) ... return loss, logits >>> grad_fn = mindspore.value_and_grad(forward_fn, None, optimizer.parameters, has_aux=True) >>> def train_step(data, label): ... (loss, _), grads = grad_fn(data, label) ... optimizer(grads) ... return loss """ def __init__(self, params, lr=2e-3, betas=(0.9, 0.999), eps=1e-8, weight_decay=0.0, momentum_decay=4e-3): check_not_less_than_without_equal(lr, "lr", self.cls_name) check_not_less_than_without_equal(eps, "eps", self.cls_name) check_not_less_than(weight_decay, "weight_decay", self.cls_name) check_not_less_than(momentum_decay, "momentum_decay", self.cls_name) validator.check_float_range(betas[0], 0., 1., validator.INC_LEFT, "betas[0]", self.cls_name) validator.check_float_range(betas[1], 0., 1., validator.INC_LEFT, "betas[1]", self.cls_name) defaults = dict(lr=lr, betas=betas, eps=eps, weight_decay=weight_decay, momentum_decay=momentum_decay) super(NAdam, self).__init__(params, defaults) self.step_t = Parameter(Tensor(0, mstype.int32), "step_t") self.exp_avg = self.parameters.clone(prefix="exp_avg", init='zeros') self.exp_avg_sq = self.parameters.clone(prefix="exp_avg_sq", init='zeros') self.mu_product = [Parameter(Tensor(1.), "mu_product_" + param.name) for param in self.parameters] self.increase_tensor = Tensor(1, mstype.int32) self.assignadd = P.AssignAdd() self.op_cast = P.Cast() @jit def implementation(self, lr, beta1, beta2, weight_decay, momentum_decay, eps, start_id, end_id, gradients): """Extract the common computing part for acceleration""" params = self.parameters[start_id: end_id] grads = gradients[start_id: end_id] grads = self._decay_weight(weight_decay, params, grads) exp_avg = self.exp_avg[start_id: end_id] exp_avg_sq = self.exp_avg_sq[start_id: end_id] mu_product = self.mu_product[start_id: end_id] self.hyper_map(F.partial(_nadam_opt, beta1, beta2, momentum_decay, eps, self.step_t, lr), params, grads, exp_avg, exp_avg_sq, mu_product) return True def construct(self, gradients): self.assignadd(self.step_t, self.increase_tensor) for group_id, group in enumerate(self.param_groups): lr = self.lrs[group_id] if isinstance(group.get("lr"), float): lr = self.op_cast(group.get("lr"), mstype.float32) beta1, beta2 = group["betas"] start_id = self.group_start_id[group_id] end_id = self.group_start_id[group_id + 1] weight_decay = group["weight_decay"] momentum_decay = group["momentum_decay"] eps = group["eps"] self.implementation(lr, beta1, beta2, weight_decay, momentum_decay, eps, start_id, end_id, gradients) return True