module Cov_lin_ard: Gpr_cov_lin_ard
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:Eval
with type Kernel.params = Params.t
with type Inducing.t = mat
with type Input.t = vec
with type Inputs.t = mat
module Deriv:Deriv
with module Eval = Eval
with type Hyper.t = [ `Log_ell of int ]