Combinatorial Pen Testing (or Consumer Surplus of Deferred-Acceptance Auctions)
Aadityan Ganesh, Jason Hartline
TL;DR
The paper studies combinatorial pen testing, where one selects high-ink pens under testing costs, and shows how to leverage deferred-acceptance auction theory to obtain near-optimal algorithms. It introduces a black-box reduction that turns surplus-optimal (or near-optimal) deferred-acceptance mechanisms into pen-testing procedures with equivalent performance guarantees, achieving an omniscient approximation of $(1+o(1)) \ln n$ and extending to matroid, knapsack, and online settings. The authors derive environment-specific refinements (e.g., matroids with $\beta(M)$, $k$-identical goods, downward-closed constraints, and online IID) and show substantial improvements over prior results (notably compared to QV23) by connecting mechanism design to pen testing. Overall, the framework provides principled, transferable tools for maximizing residual ink under diverse combinatorial constraints while clarifying the fundamental links between surplus in auctions and residual value in testing.
Abstract
Pen testing is the problem of selecting high-capacity resources when the only way to measure the capacity of a resource expends its capacity. We have a set of $n$ pens with unknown amounts of ink and our goal is to select a feasible subset of pens maximizing the total ink in them. We are allowed to learn about the ink levels by writing with them, but this uses up ink that was previously in the pens. We identify optimal and near optimal pen testing algorithms by drawing analogues to auction theoretic frameworks of deferred-acceptance auctions and virtual values. Our framework allows the conversion of any near optimal deferred-acceptance mechanism into a near optimal pen testing algorithm. Moreover, these algorithms guarantee an additional overhead of at most $(1+o(1)) \ln n$ in the approximation factor to the omniscient algorithm that has access to the ink levels in the pens. We use this framework to give pen testing algorithms for various combinatorial constraints like matroid, knapsack, and general downward-closed constraints, and also for online environments.
