A Quasi-Polynomial Approximation For The Restricted Assignment Problem

The RESTRICTED ASSIGNMENT problem is a prominent special case of SCHEDULING ON UNRELATED PARALLEL MACHINES. For the strongest known linear programming relaxation, the configuration LP, we improve the nonconstructive bound on its integrality gap from 1.9412 to 1.8334 and significantly simplify the proof. Then we give a constructive variant, yielding a 1.8334-approximation in quasi-polynomial time. This is the first quasi-polynomial algorithm for this problem improving on the long-standing approximation rate of 2.