Dynamic Algorithms for Packing-Covering LPs via Multiplicative Weight Updates

TL;DR

This paper develops near-optimal dynamic algorithms for general packing and covering linear programs using multiplicative weights updates, achieving polylogarithmic update times and extending to online and streaming settings.

Contribution

It introduces the first non-trivial dynamic algorithms for general packing and covering LPs with near-optimal update times, and systematically studies MWU in dynamic, online, and streaming contexts.

Findings

Achieves polylogarithmic amortized update time for dynamic LPs.

Provides the first online $(1+)$-competitive algorithms for LPs.

Develops streaming algorithms with linear space and polylogarithmic passes.

Abstract

In the dynamic linear program (LP) problem, we are given an LP undergoing updates and we need to maintain an approximately optimal solution. Recently, significant attention (e.g., [Gupta et al. STOC'17; Arar et al. ICALP'18, Wajc STOC'20]) has been devoted to the study of special cases of dynamic packing and covering LPs, such as the dynamic fractional matching and set cover problems. But until now, there is no non-trivial dynamic algorithm for general packing and covering LPs. In this paper, we settle the complexity of dynamic packing and covering LPs, up to a polylogarithmic factor in update time. More precisely, in the partially dynamic setting (where updates can either only relax or only restrict the feasible region), we give near-optimal deterministic $\epsilon$-approximation algorithms with polylogarithmic amortized update time. Then, we show that both partially dynamic updates and amortized update time are necessary; without any of these conditions, the trivial algorithm that recomputes the solution from scratch after every update is essentially the best possible, assuming SETH. To obtain our results, we initiate a systematic study of the multiplicative weights update (MWU) method in the dynamic setting. As by-products of our techniques, we also obtain the first online $(1+\epsilon)$-competitive algorithms for both covering and packing LPs with polylogarithmic recourse, and the first streaming algorithms for covering and packing LPs with linear space and polylogarithmic passes.