• Simulation-based : a simulation constraint is one in which a costly procedure is involved with evaluating the constraint for a set of parameters. Although infeasible experiments may overall be cheaper to evaluate than feasible ones, we assume some nonnegligible effort that one would prefer to avoid, if possible. For example, in a molecular design task in which evaluation of the objective function (e.g. a bioassay) follows the synthesis of a drug molecule, the a priori unknown synthetic feasibility constraint function is evaluated directly after the attempted synthesis.