This function is based on the defintion $$f(\mathbf{x}) = \frac{1}{2} \sum_{i = 1}^{2} (\mathbf{x}_i^4 - 16 \mathbf{x}_i^2 + 5\mathbf{x}_i)$$ with box-constraints given by \(\mathbf{x}_i \in [-5, 5], i = 1, 2\).
makeStyblinkskiTangFunction()[smoof_single_objective_function]
Z. K. Silagadze, Finding Two-Dimesnional Peaks, Physics of Particles and Nuclei Letters, vol. 4, no. 1, pp. 73-80, 2007.