Dear All,

I am a beginner and learning to apply Gaussian processes. I find in pymc3 the periodic kernel is implemented through:

However, in other sources including David Duvenaud’s Kernel Cookbook, as well as one place in pymc3 documentation - the formula is given by:

I am a little confused here. Does this difference (placement of “2”) change the interpretation of the lengthscale (\ell)? Or am I simply missing something?

Thank you!