Loss scale manager with a fixed loss scale.
The loss scale is not updated for the lifetime of the class.
Creates the fixed loss scale manager.
loss_scale: A Python float. Its ideal value varies depending on models to run. Choosing a too small loss_scale might affect model quality; a too big loss_scale might cause inf or nan. There is no single right loss_scale to apply. There is no harm choosing a relatively big number as long as no nan or inf is encountered in training.
ValueError: If loss_scale is less than 1.