 Here, the portfolio of algorithms is a set of (complementary) SAT solvers, the instances are Boolean formulas, the cost metric is for example average runtime or number of unsolved instances.So, the goal is to select a well-performing SAT solver for each individual instance.In the same way, algorithm selection can be applied to many other formula_9-hard problems (such as mixed integer programming, CSP, AI planning, TSP, MAXSAT, QBF and answer set programming).