Branch-and-bound algorithms (B&B) and polynomial-time approximation schemes (PTAS) are two seemingly distant areas of combinatorial optimization. We intend to (partially) bridge the gap between them while expanding the boundary of theoretical knowledge on the B&B framework. Branch-and-bound algorithms typically guarantee that an optimal solution is eventually found. However, we show that the standard implementation of branch-and-bound for certain knapsack and scheduling problems also exhibits PTAS-like behaviour, yielding increasingly better solutions within polynomial time. Our findings are supported by computational experiments and comparisons with benchmark methods.
@InProceedings{encz_et_al:LIPIcs.ICALP.2025.73, author = {Encz, Kopp\'{a}ny Istv\'{a}n and Mastrolilli, Monaldo and Vercesi, Eleonora}, title = {{Branch-And-Bound Algorithms as Polynomial-Time Approximation Schemes}}, booktitle = {52nd International Colloquium on Automata, Languages, and Programming (ICALP 2025)}, pages = {73:1--73:19}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-372-0}, ISSN = {1868-8969}, year = {2025}, volume = {334}, editor = {Censor-Hillel, Keren and Grandoni, Fabrizio and Ouaknine, Jo\"{e}l and Puppis, Gabriele}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2025.73}, URN = {urn:nbn:de:0030-drops-234502}, doi = {10.4230/LIPIcs.ICALP.2025.73}, annote = {Keywords: Branch-and-bound algorithm, Polynomial-time approximation scheme, Parallel machine scheduling problem, Knapsack problem} }
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