This interface specifies how to check if an optimization algorithm has converged.
Deciding if convergence has been reached is a problem-dependent issue. The user should provide a class implementing this interface to allow the optimization algorithm to stop its search according to the problem at hand.
For convenience, three implementations that fit simple needs are already provided: SimpleValueChecker, SimpleVectorValueChecker and SimplePointChecker. The first two consider that convergence is reached when the objective function value does not change much anymore, it does not use the point set at all. The third one considers that convergence is reached when the input point set does not change much anymore, it does not use objective function value at all.