mindspore.experimental.optim.Optimizer

class mindspore.experimental.optim.Optimizer(params, defaults)

Base class for all optimizers.

Warning

This is an experimental optimizer API that is subject to change. This module must be used with lr scheduler module in LRScheduler Class .

Parameters

• params (Union[list(Parameter), list(dict)]) – an iterable of mindspore.Parameter or dict. Specifies what Tensors should be optimized.

• defaults (dict) – a dict containing default values of optimization options (used when a parameter group doesn’t specify them).

Supported Platforms:

Ascend GPU CPU

Examples

>>> import numpy as np
>>> import mindspore
>>> from mindspore import nn, Tensor, Parameter
>>> from mindspore import ops
>>> from mindspore.experimental import optim
>>>
>>> class MySGD(optim.Optimizer):
...    def __init__(self, params, lr):
...        defaults = dict(lr=lr)
...        super(MySGD, self).__init__(params, defaults)
...
...    def construct(self, gradients):
...         for group_id, group in enumerate(self.param_groups):
...            id = self.group_start_id[group_id]
...            for i, param in enumerate(group["params"]):
...                next_param = param + gradients[id+i] * group["lr"]
...                ops.assign(param, next_param)
>>>
>>> net = nn.Dense(8, 2)
>>> data = Tensor(np.random.rand(20, 8).astype(np.float32))
>>> label = Tensor(np.random.rand(20, 2).astype(np.float32))
>>>
>>> optimizer = MySGD(net.trainable_params(), 0.01)
>>> optimizer.add_param_group({"params": Parameter([0.01, 0.02])})
>>>
>>> criterion = nn.MAELoss(reduction="mean")
>>>
>>> def forward_fn(data, label):
...    logits = net(data)
...    loss = criterion(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)
...    print(loss)
>>>
>>> train_step(data, label)

add_param_group(param_group)

Add a param group to the Optimizer.param_groups.

Parameters

param_group (dict) – Specifies what Parameters should be optimized along with group specific optimization options.