Optimal common due-date with limited completion time

Abstract

T.C.E. Cheng [ Computers Ops Res. 15, 91–96 (1988)] recently presented an interesting variation of the common due-date scheduling problem. He considered the situation where jobs that only marginally miss the common due-date are not penalized. His major conclusion, as given in Lemma 1, is a sufficient but not necessary requirement for optimality. We prove that alternate optima exist.