Abstract

We consider the problem of scheduling jobs on unrelated machines so as to minimize the sum of weighted completion times. Our main result is a (3/2-c)-approximation algorithm for some fixed c > 0, improving upon the long-standing bound of 3/2. To do this, we first introduce a new lift-and-project-based SDP relaxation for the problem. This is necessary, as the previous convex programming relaxations have an integrality gap of 3/2. Second, we give a new general bipartiterounding procedure that produces an assignment with certain strong negative correlation properties.

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