Two-dimensional, unimodal test function $$f(\mathbf{x}) = 0.26 (\mathbf{x}_1^2 + \mathbf{x}_2^2) - 0.48\mathbf{x}_1\mathbf{x}_2$$ subject to \(\mathbf{x}_i \in [-10, 10], i = 1, 2\).
makeMatyasFunction()[smoof_single_objective_function]
A.-R. Hedar, Global Optimization Test Problems.