“…As calibration is an optimization problem, its implementation is identified by the choice of its objective function, its constraints and the algorithm used. Algorithms for such global minimization problems are heuristic methods of mainly three types, i.e., stochastic search, multi-start and surrogate (see e.g., Pintér (2006) and Kochenderfer and Wheeler (2019) textbooks), while objective function can be modified to include penalty terms if a regularization of the problem is desired (see e.g., Tikhonov (1963)). These choices are necessarily model-dependent, as each log-return distribution can lead to different levels of non-convexity of the objective function.…”