tf.train.cosine_decay

tf.train.cosine_decay(
    learning_rate,
    global_step,
    decay_steps,
    alpha=0.0,
    name=None
)

Defined in tensorflow/python/training/learning_rate_decay.py.

See the guide: Training > Decaying the learning rate

Applies cosine decay to the learning rate.

See [Loshchilov & Hutter, ICLR2016], SGDR: Stochastic Gradient Descent with Warm Restarts. https://arxiv.org/abs/1608.03983

When training a model, it is often recommended to lower the learning rate as the training progresses. This function applies a cosine decay function to a provided initial learning rate. It requires a global_step value to compute the decayed learning rate. You can just pass a TensorFlow variable that you increment at each training step.

The function returns the decayed learning rate. It is computed as:

global_step = min(global_step, decay_steps)
cosine_decay = 0.5 * (1 + cos(pi * global_step / decay_steps))
decayed = (1 - alpha) * cosine_decay + alpha
decayed_learning_rate = learning_rate * decayed

Example usage:

decay_steps = 1000
lr_decayed = cosine_decay(learning_rate, global_step, decay_steps)

Args:

  • learning_rate: A scalar float32 or float64 Tensor or a Python number. The initial learning rate.
  • global_step: A scalar int32 or int64 Tensor or a Python number. Global step to use for the decay computation.
  • decay_steps: A scalar int32 or int64 Tensor or a Python number. Number of steps to decay over.
  • alpha: A scalar float32 or float64 Tensor or a Python number. Minimum learning rate value as a fraction of learning_rate.
  • name: String. Optional name of the operation. Defaults to 'CosineDecay'.

Returns:

A scalar Tensor of the same type as learning_rate. The decayed learning rate.

Raises:

  • ValueError: if global_step is not supplied.