Adjustable Paciorek

Implementation of the adjustable bi-fidelity Paciorek function as defined in:

Toal, D.J.J. Some considerations regarding the use of multi- fidelity Kriging in the construction of surrogate models. Struct Multidisc Optim 51, 1223–1245 (2015) doi:10.1007/s00158-014-1209-5

Function definitions:

\[f_h(x_1, x_2) = \sin \Big( \dfrac{1}{x_1x_2} \Big)\]

\[f_l(x_1, x_2) = f_h(x_1, x_2) - 9a^2\cos \Big( \dfrac{1}{x_1x_2} \Big)\]

where \(a \in (0, 1]\) is the adjustable parameter

adjustable_paciorek_lf(xx, a)

paciorek_hf(xx)