module Cov_lin_ard:sig..end
k(x, y) = x*inv(P)*y
where P is a diagonal matrix containing ARD parameters ell_1^2,...,ell_D^2,
and D is the dimensionality of the input space.
module Params:sig..end
module Eval:Evalwith type Kernel.params = Params.twith type Inducing.t = matwith type Input.t = vecwith type Inputs.t = mat
module Deriv:Derivwith module Eval = Evalwith type Hyper.t = [ `Log_ell of int ]