An Invitation to the Dance It is an underappreciated fact that sets may have various types of complex ity, and not all types are in harmony with each other. The primary goal of this book is to unify and make more widely accessible a vibrant stream of research-the theory of semi-feasible computation-that perfectly showcases the richness of, and contrasts between, the central types of complexity. The semi-feasible sets, which are most commonly referred to as the P selective sets, are those sets L for which there is a deterministic polynornial time algorithm that, when given as input any two...