LRScheduler¶
- class paddle.callbacks. LRScheduler ( by_step=True, by_epoch=False ) [源代码] ¶
-
LRScheduler
是一个学习率回调函数。
参数¶
by_step (bool,可选) - 是否每个 step 都更新学习率。默认值:True。
by_epoch (bool,可选) - 是否每个 epoch 都更新学习率。默认值:False。
代码示例¶
import paddle
import paddle.vision.transforms as T
from paddle.static import InputSpec
inputs = [InputSpec([-1, 1, 28, 28], 'float32', 'image')]
labels = [InputSpec([None, 1], 'int64', 'label')]
transform = T.Compose([
T.Transpose(),
T.Normalize([127.5], [127.5])
])
train_dataset = paddle.vision.datasets.MNIST(mode='train', transform=transform)
lenet = paddle.vision.models.LeNet()
model = paddle.Model(lenet,
inputs, labels)
base_lr = 1e-3
boundaries = [5, 8]
wamup_steps = 4
def make_optimizer(parameters=None):
momentum = 0.9
weight_decay = 5e-4
values = [base_lr * (0.1**i) for i in range(len(boundaries) + 1)]
learning_rate = paddle.optimizer.lr.PiecewiseDecay(
boundaries=boundaries, values=values)
learning_rate = paddle.optimizer.lr.LinearWarmup(
learning_rate=learning_rate,
warmup_steps=wamup_steps,
start_lr=base_lr / 5.,
end_lr=base_lr,
verbose=True)
optimizer = paddle.optimizer.Momentum(
learning_rate=learning_rate,
weight_decay=weight_decay,
momentum=momentum,
parameters=parameters)
return optimizer
optim = make_optimizer(parameters=lenet.parameters())
model.prepare(optimizer=optim,
loss=paddle.nn.CrossEntropyLoss(),
metrics=paddle.metric.Accuracy())
# if LRScheduler callback not set, an instance LRScheduler update by step
# will be created auto.
model.fit(train_dataset, batch_size=64)
# create a learning rate scheduler update by epoch
callback = paddle.callbacks.LRScheduler(by_step=False, by_epoch=True)
model.fit(train_dataset, batch_size=64, callbacks=callback)