Generalized budgeted submodular set function maximization

TL;DR

This paper introduces approximation algorithms for a generalized budgeted submodular maximization problem involving elements and bins, achieving near-optimal guarantees under various cost conditions.

Contribution

It presents new polynomial-time algorithms with improved approximation ratios for a generalized budgeted submodular maximization problem, extending previous work with bi-criterion guarantees.

Findings

Achieves a 1/2(1-1/e^α) approximation ratio.

Provides two algorithms with α=1-ε and α=1-1/e-ε under different conditions.

Extends to a bi-criterion approximation with adjustable budget factor β.

Abstract

In this paper we consider a generalization of the well-known budgeted maximum coverage problem. We are given a ground set of elements and a set of bins. The goal is to find a subset of elements along with an associated set of bins, such that the overall cost is at most a given budget, and the profit is maximized. Each bin has its own cost and the cost of each element depends on its associated bin. The profit is measured by a monotone submodular function over the elements. We first present an algorithm that guarantees an approximation factor of $\frac{1}{2}\left(1-\frac{1}{e^\alpha}\right)$, where $\alpha \leq 1$ is the approximation factor of an algorithm for a sub-problem. We give two polynomial-time algorithms to solve this sub-problem. The first one gives us $\alpha=1- \epsilon$ if the costs satisfies a specific condition, which is fulfilled in several relevant cases, including the unitary costs case and the problem of maximizing a monotone submodular function under a knapsack constraint. The second one guarantees $\alpha=1-\frac{1}{e}-\epsilon$ for the general case. The gap between our approximation guarantees and the known inapproximability bounds is $\frac{1}{2}$. We extend our algorithm to a bi-criterion approximation algorithm in which we are allowed to spend an extra budget up to a factor $\beta\geq 1$ to guarantee a $\frac{1}{2}\left(1-\frac{1}{e^{\alpha\beta}}\right)$-approximation. If we set $\beta=\frac{1}{\alpha}\ln \left(\frac{1}{2\epsilon}\right)$, the algorithm achieves an approximation factor of $\frac{1}{2}-\epsilon$, for any arbitrarily small $\epsilon>0$.