STK_TESTFUN_GOLDSTEINPRICE computes the Goldstein-Price function

    The Goldstein-Price function [1] is a classical test function for
    global optimization algorithms, which belongs to the well-known
    Dixon-Szego test set [2].

    It is usually minimized over [-2; 2] x [-2; 2]. It has a unique
    global minimum at x = [0, -1] with f(x) = 3, and several local minima.

 REFERENCES

  [1] Goldstein, A.A. and Price, I.F. (1971), On descent from local
      minima. Mathematics of Computation, 25(115).

  [2] Dixon L.C.W., Szego G.P. (1978), Towards Global Optimization 2,
      North-Holland, Amsterdam, The Netherlands