Frugal and Truthful Auctions for Vertex Covers, Flows, and Cuts

TL;DR

This paper introduces constant-competitive truthful mechanisms for Vertex Cover, k-flow, and cut auctions, ensuring near-optimal overpayment bounds while maintaining truthfulness in strategic settings.

Contribution

It develops novel, constant-competitive truthful mechanisms for three complex set system auctions, extending prior work with innovative graph transformations and eigenvector-based scaling.

Findings

Mechanism for Vertex Cover uses eigenvector scaling.

Graph pruning for k-flows ensures minimal connectivity.

Graph contraction for cuts standardizes s-t path lengths.

Abstract

We study truthful mechanisms for hiring a team of agents in three classes of set systems: Vertex Cover auctions, k-flow auctions, and cut auctions. For Vertex Cover auctions, the vertices are owned by selfish and rational agents, and the auctioneer wants to purchase a vertex cover from them. For k-flow auctions, the edges are owned by the agents, and the auctioneer wants to purchase k edge-disjoint s-t paths, for given s and t. In the same setting, for cut auctions, the auctioneer wants to purchase an s-t cut. Only the agents know their costs, and the auctioneer needs to select a feasible set and payments based on bids made by the agents. We present constant-competitive truthful mechanisms for all three set systems. That is, the maximum overpayment of the mechanism is within a constant factor of the maximum overpayment of any truthful mechanism, for every set system in the class. The mechanism for Vertex Cover is based on scaling each bid by a multiplier derived from the dominant eigenvector of a certain matrix. The mechanism for k-flows prunes the graph to be minimally (k+1)-connected, and then applies the Vertex Cover mechanism. Similarly, the mechanism for cuts contracts the graph until all s-t paths have length exactly 2, and then applies the Vertex Cover mechanism.