ยป Keras API reference / Callbacks API / LearningRateScheduler

LearningRateScheduler

LearningRateScheduler class

tf.keras.callbacks.LearningRateScheduler(schedule, verbose=0)

Learning rate scheduler.

At the beginning of every epoch, this callback gets the updated learning rate value from schedule function provided at __init__, with the current epoch and current learning rate, and applies the updated learning rate on the optimizer.

Arguments

  • schedule: a function that takes an epoch index (integer, indexed from 0) and current learning rate (float) as inputs and returns a new learning rate as output (float).
  • verbose: int. 0: quiet, 1: update messages.

Example

>>> # This function keeps the initial learning rate for the first ten epochs  
>>> # and decreases it exponentially after that.  
>>> def scheduler(epoch, lr):
...   if epoch < 10:
...     return lr
...   else:
...     return lr * tf.math.exp(-0.1)
>>>
>>> model = tf.keras.models.Sequential([tf.keras.layers.Dense(10)])
>>> model.compile(tf.keras.optimizers.SGD(), loss='mse')
>>> round(model.optimizer.lr.numpy(), 5)
0.01

>>> callback = tf.keras.callbacks.LearningRateScheduler(scheduler)
>>> history = model.fit(np.arange(100).reshape(5, 20), np.zeros(5),
...                     epochs=15, callbacks=[callback], verbose=0)
>>> round(model.optimizer.lr.numpy(), 5)
0.00607