Optimization-friendly generic mechanisms without money
This work addresses mechanism design for multi-agent systems without monetary transfers, which is incremental but offers theoretical insights for domains like voting and resource allocation.
The paper tackles the problem of converting optimization algorithms into mechanisms for self-interested agents without money, focusing on preference aggregation in contexts like voting and allocation. It introduces the APEX meta-algorithm and strengthens a 1979 result on competitive equilibrium from equal incomes by showing a connection to VCG prices and providing a simpler proof using Brouwer's fixed point theorem.
The goal of this paper is to develop a generic framework for converting modern optimization algorithms into mechanisms where inputs come from self-interested agents. We focus on aggregating preferences from $n$ players in a context without money. Special cases of this setting include voting, allocation of items by lottery, and matching. Our key technical contribution is a new meta-algorithm we call \apex (Adaptive Pricing Equalizing Externalities). The framework is sufficiently general to be combined with any optimization algorithm that is based on local search. We outline an agenda for studying the algorithm's properties and its applications. As a special case of applying the framework to the problem of one-sided assignment with lotteries, we obtain a strengthening of the 1979 result by Hylland and Zeckhauser on allocation via a competitive equilibrium from equal incomes (CEEI). The [HZ79] result posits that there is a (fractional) allocation and a set of item prices such that the allocation is a competitive equilibrium given prices. We further show that there is always a reweighing of the players' utility values such that running unit-demand VCG with reweighed utilities leads to a HZ-equilibrium prices. Interestingly, not all HZ competitive equilibria come from VCG prices. As part of our proof, we re-prove the [HZ79] result using only Brouwer's fixed point theorem (and not the more general Kakutani's theorem). This may be of independent interest.