Improved online algorithms for the batch scheduling of equal-length jobs with incompatible families to maximize the weighted number of early jobs

Abstract

We consider the online scheduling of equal-length jobs with incompatible families on $m$ identical batch machines. Each job has a release time, a deadline and a weight. Each batch machine can process up to $b$ jobs (which come from the same family) simultaneously as a batch, where $b$ is called the capacity of the machines. Our goal is to determine a preemption-restart schedule which maximizes the weighted number of early jobs. For this problem, Li et al. (Inf Process Lett 112:503–508, 2012) provided an online algorithm of competitive ratio $3+2\sqrt{2}$ for both $b=\infty$ and $b<\infty$. In this paper, we study two special cases of this problem. For the case that $m=2$, we first present a lower bound 2, and then provide an online algorithm with a competitive ratio of 3 for both $b=\infty$ and $b<\infty$. For the case in which $m=3$, $b=\infty$ and all jobs come from a common family, we present an online algorithm with a competitive ratio of $(8+2\sqrt{15})/3\approx 5.249$.