An exact vertex cover solver using kernels

An exact vertex cover solver was implemented in C++. It is based on a simple search tree algorithm, extended with multiple reduction rules and lower bounds. The former include some standard ruleslike the degree one and unconfined vertex rule, but also rather new ones such as clique neighbourhoodand degree three. The lower bounds consist of a clique cover heuristic and one based on integerprogramming. About 40 out of 100 PACE test instances could be solved.