  We study the problem of preemptive scheduling of n equal-length jobs with
given release times on m identical parallel machines. The objective is to
minimize the average flow time. Recently, Brucker and Kravchenko proved that
the optimal schedule can be computed in polynomial time by solving a linear
program with O(n^3) variables and constraints, followed by some substantial
post-processing (where n is the number of jobs.) In this note we describe a
simple linear program with only O(mn) variables and constraints. Our linear
program produces directly the optimal schedule and does not require any
post-processing.
