Unit propagation is known to be one of the most time-consuming procedures inside CDCL-based SAT solvers. Not surprisingly, it has been studied in depth and the two-watched-literal scheme, enhanced with implementation details boosting its performance, has emerged as the dominant method. In pseudo-Boolean solvers, the importance of unit propagation is similar, but no dominant method exists: counter propagation and watched-based extensions are efficient for different types of constraints, which has opened the door to hybrid methods. However, probably due to the higher complexity of implementing pseudo-Boolean solvers, research efforts have not focused much on concrete implementation details for unit propagation but rather on higher-level aspects of other procedures, such as conflict analysis. In this paper, we present (i) a novel methodology to precisely assess the performance of propagation mechanisms, (ii) an evaluation of implementation variants of the propagation methods present in {RoundingSat} and (iii) a detailed analysis showing that hybrid methods outperform the ones based on a single technique. Our final contribution is to show that a carefully implemented hybrid propagation method is considerably faster than the preferred propagation mechanism in {RoundingSat}, and that this improvement leads to a better overall performance of the solver.
@InProceedings{nieuwenhuis_et_al:LIPIcs.SAT.2024.22, author = {Nieuwenhuis, Robert and Oliveras, Albert and Rodr{\'\i}guez-Carbonell, Enric and Zhao, Rui}, title = {{Speeding up Pseudo-Boolean Propagation}}, booktitle = {27th International Conference on Theory and Applications of Satisfiability Testing (SAT 2024)}, pages = {22:1--22:18}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-334-8}, ISSN = {1868-8969}, year = {2024}, volume = {305}, editor = {Chakraborty, Supratik and Jiang, Jie-Hong Roland}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SAT.2024.22}, URN = {urn:nbn:de:0030-drops-205449}, doi = {10.4230/LIPIcs.SAT.2024.22}, annote = {Keywords: SAT, Pseudo-Boolean Solving, Implementation-level Details} }
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