News
MallobSat scores 1st in SAT CompetitionMallobSat scores 1st in SAT Competition
August 20, 2025
This year's authors of MallobSat (D. Schreiber, N. Rigi-Luperti, A. Biere) during the SAT/CP/SoCS social event in the Kelvingrove Art Gallery and Museum, Glasgow, Scotland.
Our latest, simplified version of MallobSat was the best performing parallel solver in the International SAT Competition 2025.
This year’s competition did not feature a distributed “Cloud” track (1600 threads), in which MallobSat has consistently scored the best since 2020. As such, it marked a transitional year for MallobSat, too, and we somewhat jokingly titled our solver description “MallobSat naps in the SAT Competition 2025” (a word play on “naps” = “not a portfolio solver”).
That being said, 2025 marks the first year where our system was able to win the SAT competition’s shared-memory parallel main track (64 threads). This result highlights how MallobSat is a promising tool even for users who are interested “only” in shared-memory parallelization rather than large-scale distributed computing.
MallobSat scored the best on unsatisfiable instances and the 2nd best on satisfiable instances (after Painless-PRS-Kissat by Saoudi et al.), overall resulting in a 1st place by a rather small margin (3% to Painless-PRS-Kissat in terms of the PAR-2 evaluation metric).
In line with our SAT'25 best paper, our submission features a simplified and streamlined parallel solver design. MallobSat employs minimal solver diversification (random seeds and variable phases only) and sequential preprocessors followed by parallel search-only Kissat threads (without any pre-/inprocessing) plus a few “needle-in-the-haystack” YalSAT stochastic local search threads. This setup departs from the prevalent notion of a “diverse portfolio” and is closer to a uniform parallel CDCL procedure, powered by clause sharing.
MallobSat’s submitted configuration is documented in our solver description; more background and details are provided in our SAT'25 paper. All rankings as well as some more details can be found in the SAT Competition results slides. Many thanks to all the organizers who made this competitive event happen once again!