Learning Rate in a Learner

Part 1 (2019) Advanced (Part 1 v3)
1

I have a few questions related to learning rate, its working in a Learner, and the max_lr parameter in fit_one_cycle() :-

  1. According to the docs, the default argument for max_lr in fit_one_cycle() is slice(None,0.03,None). So, if i pass max_lr = 0.02, is that equivalent to max_lr = slice(None, 0.02, None) i.e., the learning rate is sliced from 0 to 0.02 between the beginning and final layers or simply 0.02 ie all the layers have a learning rate of 0.02?

  2. When I pass max_lr = slice(1e-5,1e-3), it means that the first layer is trained with a lr=1e-5, the final layer with lr=1e-3, and the intermediate layers are trained with values in between 1e-5 and 1e-3. However, in the plot generated by learn.recorder.plot_lr(), a single curve is present. Which lr is shown? Is it the lr of the last layer or first layer or average of all lrs?

  3. Is there any attribute that shows the learning rate of a Learner? The closest I could find was learn.opt which shows the optimizer, which in turn showed the individual learning rate of each Parameter Group. Is there any other method to get the current learning rate(s) of a Learner?