We study the periodic assignment problem, in which a set of periodically repeating tasks must be assigned to workers within a repeating schedule. The classical efficiency objective is to minimize the number of workers required to operate the schedule. We propose a 𝒪(n log n) algorithm to solve this problem. Next, we formalize a notion of fairness among workers, and impose that each worker performs the same work over time. We analyze the resulting trade-off between efficiency and fairness, showing that the price of fairness is at most one extra worker, and that such a fair solution can always be found using the Nearest Neighbor heuristic. We characterize all instances that admit a solution that is both fair and efficient, and use this result to develop a 𝒪(n log n) exact algorithm for the fair periodic assignment problem. Finally, we show that allowing aperiodic schedules never reduces the price of fairness.
@InProceedings{vanlieshout_et_al:OASIcs.ATMOS.2025.1, author = {van Lieshout, Rolf Nelson and van Rossum, Bartholome\"{u}s Theodorus Cornelis}, title = {{The Fair Periodic Assignment Problem}}, booktitle = {25th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2025)}, pages = {1:1--1:16}, series = {Open Access Series in Informatics (OASIcs)}, ISBN = {978-3-95977-404-8}, ISSN = {2190-6807}, year = {2025}, volume = {137}, editor = {Sauer, Jonas and Schmidt, Marie}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2025.1}, URN = {urn:nbn:de:0030-drops-247574}, doi = {10.4230/OASIcs.ATMOS.2025.1}, annote = {Keywords: Cyclic scheduling, Fairness, Traveling Salesman Problem} }