Approximation Algorithms for Norm-Budgeted Packing Problems

Abstract

In recent years, much attention has been devoted to the study of optimization problems under norm-based objectives coming from the rich class of monotone, symmetric norms (and their generalizations). This work has however almost exclusively focused on covering problems, wherein one seeks to minimize the norm of the cost vector induced by a solution. We introduce and study the class of {\em norm-budgeted packing problems}, which are packing problems where the resource constraints underlying the packing problem are modeled via a {\em norm budget constraint} involving a {\em monotone, symmetric norm}. Formally, we have some elements with associated rewards and sizes, a downwards-closed collection of feasible solutions, and a budget $B$. Each solution induces a size vector, and the goal is to maximize the total reward subject to the norm-budget constraint $f(\text{size vector})\leq B$. The versatility of monotone, symmetric norms implies that a variety of classical packing problems can be captured under the umbrella of norm-budgeted packing problems. Moreover, the closure properties of monotone, symmetric norms, also enable one to encode multiple different norm-budget constraints via a single monotone, symmetric norm. We consider the norm-budgeted versions of a variety of canonical packing problems, including knapsack, matching, maximum-weight independent set in a $k$-set system, maximum generalized assignment problem (MaxGAP), and $k$-facility location, and develop a framework that allows us to obtain {\em constant-factor approximation guarantees} for these problems, and {\em PTASes for knapsack, and MaxGAP on identical and related machines}. We also develop constant-factor approximation algorithms for the {\em submodular} versions of some norm-budgeted packing problems, wherein the reward function is now specified by a monotone, submodular function.