module Cov_lin_one:sig
..end
k(x, y) = x*inv(P)*y + 1/t^2
logtheta = log(t)
where P is a diagonal matrix containing t^2
along the diagonal.
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_theta ]