An FPTAS for the minimum total weighted tardiness problem with a fixed number of distinct due dates

Given a sequencing of jobs on a single machine, each one with a weight, processing time, and a due date, the tardiness of a job is the time needed for its completion beyond its due date. We present an FPTAS for the basic scheduling problem of minimizing the total weighted tardiness when the number of distinct due dates is fixed. Previously, an FPTAS was known only for the case where all jobs have a common due date.