arXiv subjects

Mozhengfu Liu

Publications and source records attributed to Mozhengfu Liu.

3 recordsLinked to original sources

arXiv2026

Busy Time Minimization with Preemption, Migration, and One Resource Requirement

We study the Busy Machine Time with Preemption and Migration and One Resource Requirement problem, motivated by energy minimization in cloud data centers. Given unlimited identical-capacity machines and jobs with release times, deadlines, processing times, and resource requirements, we allow free preemption and migration at integer times and seek to minimize total machine busy time. The problem is NP-hard, and previous results consist of a 2-approximation, 2-competitive algorithm for the case of uniform heights. We obtain a 22/9 < 2.445-approximation algorithm and a 2.5-competitive online algorithm, both running in O(n^2 log n) time. Our methods are based on new non-asymptotic performance bounds for the First Fit Decreasing algorithm for Bin Packing, and a new generalization of Span Minimization, the Huge-Tiny Busy Time problem, for which we present an exact offline algorithm and an optimal (3/2)-competitive deterministic online algorithm.

cs.DS↗

arXiv2026

Online Span Minimization for Flexible Uniform Jobs

Motivated by the critical need for energy-efficient scheduling in cloud computing, this paper investigates Span Minimization, a fundamental variant of the well-studied BusyTime problem. In the general BusyTime problem, $n$ jobs characterized by release times, deadlines, and processing times must be partitioned into bundles of capacity $B$, where the objective is to minimize the total active duration of the virtual machines. Span minimization addresses the specific case of unbounded capacity ($B = \infty$), a problem that serves as a vital precursor for achieving high-performance approximation guarantees in more complex scheduling environments. While previous research established a deterministic $2$-approximation for interval jobs and a $3$-approximation for the general BusyTime problem, the online landscape of span minimization remains less explored. In this paper, we focus on the online version of span minimization. We demonstrate that randomization can be leveraged to break the known deterministic competitive barrier of $2$. For uniform-length jobs, we derive a randomized competitive upper bound of $\frac{1}{\ln{2}}\approx 1.443$ and a lower bound of $\frac{\sqrt{3}+1}{2}\approx 1.366$. Furthermore, we show that by introducing the ability to restart jobs, we can achieve an optimal competitive ratio equal to the golden ratio ($ϕ\approx 1.618$). Our results provide new insights into the power of randomization and flexibility in online energy-aware scheduling.

cs.DS↗

arXiv2021

Analysis of Busy-Time Scheduling on Heterogeneous Machines

This paper studies a generalized busy-time scheduling model on heterogeneous machines. The input to the model includes a set of jobs and a set of machine types. Each job has a size and a time interval during which it should be processed. Each job is to be placed on a machine for execution. Different types of machines have distinct capacities and cost rates. The total size of the jobs running on a machine must always be kept within the machine's capacity, giving rise to placement restrictions for jobs of various sizes among the machine types. Each machine used is charged according to the time duration in which it is busy, i.e., it is processing jobs. The objective is to schedule the jobs onto machines to minimize the total cost of all the machines used. We develop an $O(1)$-approximation algorithm in the offline setting and an $O(μ)$-competitive algorithm in the online setting (where $μ$ is the max/min job length ratio), both of which are asymptotically optimal.

cs.DS↗