This two-dimensional function is based on the defintion $$f(\mathbf{x}) = 2 \mathbf{x}_1^2 - 1.05 \mathbf{x}_1^4 + \frac{\mathbf{x}_1^6}{6} + \mathbf{x}_1\mathbf{x}_2 + \mathbf{x}_2^2$$ subject to \(-5 \leq \mathbf{x}_i \leq 5\).
makeThreeHumpCamelFunction()[smoof_single_objective_function]
F. H. Branin Jr., Widely Convergent Method of Finding Multiple Solutions of Simul- taneous Nonlinear Equations, IBM Journal of Research and Development, vol. 16, no. 5, pp. 504-522, 1972.