arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2202.07932cs.DScs.CC
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平行多机排序问题的复杂性

On the Complexity of Scheduling Problems With a Fixed Number of Parallel Identical Machines

Klaus Jansen, Kai Kahler

摘要:

在并行机调度中,我们给定一组工件,以及一些机器,我们的目标是为每个工件决定何时以及在哪台机器上进行调度,以最小化某些目标函数。不同的机器模型、工件特性和目标函数会导致大量的调度问题,其中许多问题是NP难的,即使对于固定数量的相同机器也是如此。在这项工作中,我们给出了大量的调度问题的条件运行时间下界,表明一些经典算法的最优性。最值得注意的是,我们表明,该算法的Lawler和Moore的$1||\sum w_jU_j$和$Pm||C_{max}$,以及算法的李和Uzsoy的$P2||\sum w_jC_j$可能是最佳的。Zhang等人的$1|Rej\leq Q|\sum w_jU_j$算法仍有很小的改进空间,Lawler的$1||\sum T_j$算法和Gens和Levner的$1||\sum w_jU_j$的FPTAS。我们还给出了$P2|any|C_{max}$的一个下界,并将Du和Leung的动态规划从$\mathcal{O}(nP^2)$改进为$\mathcal{O}(nP)$,使之与新的下界相匹配.这里,$P$是所有处理时间的总和。同样的思想也将Du和Leung的$P3|any|C_{max}$算法从$\mathcal{O}(nP^5)$改进为$\mathcal{O}(nP^2)$。虽然我们的研究结果表明,一些经典算法的最优性,他们也激励未来的研究,在最知名的算法不太匹配的下限的情况下。

英文摘要:

In parallel machine scheduling, we are given a set of jobs, together with a number of machines and our goal is to decide for each job, when and on which machine(s) it should be scheduled in order to minimize some objective function. Different machine models, job characteristics and objective functions result in a multitude of scheduling problems and many of them are NP-hard, even for a fixed number of identical machines. In this work, we give conditional running time lower bounds for a large number of scheduling problems, indicating the optimality of some classical algorithms. Most notably, we show that the algorithm by Lawler and Moore for $1||\sum w_jU_j$ and $Pm||C_{max}$, as well as the algorithm by Lee and Uzsoy for $P2||\sum w_jC_j$ are probably optimal. There is still small room for improvement for the $1|Rej\leq Q|\sum w_jU_j$ algorithm by Zhang et al., the algorithm for $1||\sum T_j$ by Lawler and the FPTAS for $1||\sum w_jU_j$ by Gens and Levner. We also give a lower bound for $P2|any|C_{max}$ and improve the dynamic program by Du and Leung from $\mathcal{O}(nP^2)$ to $\mathcal{O}(nP)$, matching this new lower bound. Here, $P$ is the sum of all processing times. The same idea also improves the algorithm for $P3|any|C_{max}$ by Du and Leung from $\mathcal{O}(nP^5)$ to $\mathcal{O}(nP^2)$. While our results suggest the optimality of some classical algorithms, they also motivate future research in cases where the best known algorithms do not quite match the lower bounds.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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