Builds and returns the bi-objective Dent test problem, which is defined as follows: $$f(\mathbf{x}) = \left(f_1(\mathbf{x}_1), f_2(\mathbf{x})\right)$$ with $$f_1(\mathbf{x}_1) = 0.5 \left( \sqrt(1 + (x_1 + x_2)^2) + \sqrt(1 + (x_1 - x_2)^2) + x_1 - x_2\right) + d$$ and $$f_1(\mathbf{x}_1) = 0.5 \left( \sqrt(1 + (x_1 + x_2)^2) + \sqrt(1 + (x_1 - x_2)^2) - x_1 + x_2\right) + d$$ where \(d = \lambda * \exp(-(x_1 - x_2)^2)\) and \(\mathbf{x}_i \in [-1.5, 1.5], i = 1, 2\).
makeDentFunction()[smoof_multi_objective_function]