,
Matti Järvisalo
Creative Commons Attribution 4.0 International license
We study generic integer programming (IP) encodings of acyclicity in directed graphs as a key constraint in various real-world problem domains. We analyze both classical and more recently-proposed generic acyclicity encodings, including Miller-Tucker-Zemlin (MTZ), feedback vertex set (FVS), vertex elimination (VE), and cycle elimination (CE) based encodings in terms of their linear programming (LP) relaxation tightness. We also introduce hybrid encodings combining sought-after properties of the individual encodings. For the hybrids, we establish tightness guarantees for their LP relaxations that interpolate smoothly between the individual encodings. Our results show that VE and CE yield equally strong relaxations and strictly dominate MTZ and FVS, while the hybrid encoding schemes become increasingly tight as the elimination prefix grows. Mapping theory to practice, we empirically evaluate the encodings on both direct IP encodings of problem domains, where acyclicity is a key constraint. The results both validate our theoretical findings and yield promising runtime performance.
@InProceedings{rankooh_et_al:LIPIcs.CP.2026.47,
author = {Rankooh, Masood Feyzbakhsh and J\"{a}rvisalo, Matti},
title = {{Revisiting Integer Programming Encodings of Acyclicity}},
booktitle = {32nd International Conference on Principles and Practice of Constraint Programming (CP 2026)},
pages = {47:1--47:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-432-1},
ISSN = {1868-8969},
year = {2026},
volume = {379},
editor = {Beldiceanu, Nicolas},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CP.2026.47},
URN = {urn:nbn:de:0030-drops-266806},
doi = {10.4230/LIPIcs.CP.2026.47},
annote = {Keywords: Operations research, integer programming encodings, acyclicity, tightness}
}
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