Second function by Price. The implementation is based on the defintion $$f(\mathbf{x}) = 1 + \sin^2(\mathbf{x}_1) + \sin^2(\mathbf{x}_2) - 0.1 \exp(-\mathbf{x}^2 - \mathbf{x}_2^2)$$ subject to \(\mathbf{x}_i \in [-10, 10], i = 1, 2\).
makePriceN2Function()[smoof_single_objective_function]
W. L. Price, A Controlled Random Search Procedure for Global Optimisation, Computer journal, vol. 20, no. 4, pp. 367-370, 1977.