mindspore.nn.polynomial_decay_lr

mindspore.nn.polynomial_decay_lr(learning_rate, end_learning_rate, total_step, step_per_epoch, decay_epoch, power, update_decay_epoch=False)

Calculates learning rate base on polynomial decay function. The learning rate for each step will be stored in a list.

For the i-th step, the formula of computing decayed_learning_rate[i] is:

$$decayed\mathrm{\_}learning\mathrm{\_}rate[i]=(learning\mathrm{\_}rate-end\mathrm{\_}learning\mathrm{\_}rate)\ast (1-tmp\mathrm{\_}epoch/tmp\mathrm{\_}decay\mathrm{\_}epoch{)}^{power}+end\mathrm{\_}learning\mathrm{\_}rate$$

Where:

$$tmp\mathrm{\_}epoch=min(current\mathrm{\_}epoch,decay\mathrm{\_}epoch)$$

$$current\mathrm{\_}epoch=floor(\frac{i}{step\mathrm{\_}per\mathrm{\_}epoch})$$

$$tmp\mathrm{\_}decay\mathrm{\_}epoch=decay\mathrm{\_}epoch$$

If update_decay_epoch is true, update the value of $tmp\mathrm{\_}decay\mathrm{\_}epoch$ every epoch. The formula is:

$$tmp\mathrm{\_}decay\mathrm{\_}epoch=decay\mathrm{\_}epoch\ast ceil(current\mathrm{\_}epoch/decay\mathrm{\_}epoch)$$

Parameters

• learning_rate (float) – The initial value of learning rate.

• end_learning_rate (float) – The end value of learning rate.

• total_step (int) – The total number of steps.

• step_per_epoch (int) – The number of steps in per epoch.

• decay_epoch (int) – Number of epochs to decay over.

• power (float) – The power of polynomial. It must be greater than 0.

• update_decay_epoch (bool) – If true, update decay_epoch. Default: False .

Returns

list[float]. The size of list is total_step.

Raises

• TypeError – If learning_rate or end_learning_rate or power is not a float.

• TypeError – If total_step or step_per_epoch or decay_epoch is not an int.

• TypeError – If update_decay_epoch is not a bool.

• ValueError – If learning_rate or power is not greater than 0.

Supported Platforms:

Ascend GPU CPU

Examples

>>> import mindspore.nn as nn
>>>
>>> lr = 0.1
>>> end_learning_rate = 0.01
>>> total_step = 6
>>> step_per_epoch = 2
>>> decay_epoch = 2
>>> power = 0.5
>>> lr = nn.polynomial_decay_lr(lr, end_learning_rate, total_step, step_per_epoch, decay_epoch, power)
>>> net = nn.Dense(2, 3)
>>> optim = nn.SGD(net.trainable_params(), learning_rate=lr)