Function Differences with tf.train.MomentumOptimizer

tf.train.MomentumOptimizer

class tf.train.MomentumOptimizer(
    learning_rate,
    momentum,
    use_locking=False,
    name='Momentum',
    nesterov=False
)

For more information, see tf.train.MomentumOptimizer.

mindspore.nn.Momentum

class mindspore.nn.Momentum(
    params,
    learning_rate
    momentum,
    weight_decay=0.0,
    loss_scale=1.0,
    use_nesterov=False
)(grads)

For more information, see mindspore.nn.Momentum.

Differences

TensorFlow: Using the same learning rate for all parameters and it is impossible to use different learning rates for different parameter groups.

MindSpore: Using the same learning rate for all parameters and different values for different parameter groups is supported.

Code Example

# The following implements Momentum with MindSpore.
import tensorflow as tf
import mindspore.nn as nn
from mindspore import Tensor, Parameter
from mindspore import Model

net = Net()
#1) All parameters use the same learning rate and weight decay
optim = nn.Momentum(params=net.trainable_params(), learning_rate=0.1, momentum=0.9)

#2) Use parameter groups and set different values
conv_params = list(filter(lambda x: 'conv' in x.name, net.trainable_params()))
no_conv_params = list(filter(lambda x: 'conv' not in x.name, net.trainable_params()))
group_params = [{'params': conv_params, 'weight_decay': 0.01, 'grad_centralization':True},
                {'params': no_conv_params, 'lr': 0.01},
                {'order_params': net.trainable_params()}]
optim = nn.Momentum(group_params, learning_rate=0.1, weight_decay=0.0)
# The conv_params's parameters will use default learning rate of 0.1 and weight decay of 0.01 and grad
# centralization of True.
# The no_conv_params's parameters will use learning rate of 0.01 and default weight decay of 0.0 and grad
# centralization of False.
# The final parameters order in which the optimizer will be followed is the value of 'order_params'.

loss = nn.SoftmaxCrossEntropyWithLogits()
model = Model(net, loss_fn=loss, optimizer=optim)

# The following implements MomentumOptimizer with TensorFlow.
image = tf.keras.layers.Input(shape=(28, 28, 1))
model = tf.keras.models.Model(image, net)
optim = tf.train.MomentumOptimizer(learning_rate=0.1, momentum=0.9)
loss = tf.keras.losses.BinaryCrossentropy()
model.compile(optimizer=optim, loss=loss, metrics=['accuracy'])