Here, we introduce a model problem, the semi-coercive scalar variational inequality, describe its discretization and decomposition into subdomains and clusters, reduce the problem by duality to the bound and equality-constrained QP problem, and report some theoretical and numerical results. The results show the unique efficiency of the SMALBE/MPRGP algorithms combined with the FETI methods. The numerical experiments include the bound and/or equality QP problems discretized by billions of nodal variables and a challenging roller-bearing problem with floating bodies and dual degenerate solution.