We will be exploring a generalization of real time scheduling problem sometimes called the real time throughput maximization problem. Our input is a sequence of jobs specified by their release time, deadline and processing time. We assume that jobs are announced before or at their release time. At each time step, the algorithm must decide whether to schedule a job based on the information so far. The goal is to maximize the value of the sum of the processing times of jobs that finish before their deadline, or the total ``active'' time. We extend this problem by defining a notion of $t$-advance-notice, a measure of how far in advance each job is given relative to their processing time. We show that there exists a $\frac{t}{2t+1}$-competitive algorithm when all jobs have $t$-advance-notice for $t\in [0,1]$. We also show that this ratio is optimal for all algorithms with $t$-advance-notice and that the upper bound of $\frac{t}{2t+1}$-competitiveness holds for all $t$, in particular that regardless of how much advance-notice is given, no algorithm can reach $\frac{1}{2}$-competitiveness.
翻译:本文探讨一种实时调度问题的泛化形式,通常称为实时吞吐量最大化问题。输入为一组作业序列,每个作业由其释放时间、截止时间和处理时间定义。我们假设作业在其释放时间之前或之时被通知。在每个时间步,算法必须根据当前已知信息决定是否调度某个作业。目标是在截止时间前完成的作业处理时间之和(即总“活跃”时间)最大化。我们通过定义$t$-提前通知的概念扩展了该问题,该概念度量每个作业相对于其处理时间的提前通知程度。我们证明,当所有作业具有$t$-提前通知($t\in [0,1]$)时,存在一个$\frac{t}{2t+1}$-竞争算法。同时,我们证明该比率对所有具有$t$-提前通知的算法是最优的,且$\frac{t}{2t+1}$-竞争性的上界对所有$t$均成立,特别地,无论提前通知量多少,任何算法都无法达到$\frac{1}{2}$-竞争性。