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Documents authored by Chew, Leroy

Document
DOI: 10.4230/LIPIcs.SAT.2022.10
Relating Existing Powerful Proof Systems for QBF

Authors: Leroy Chew and Marijn J. H. Heule

Published in: LIPIcs, Volume 236, 25th International Conference on Theory and Applications of Satisfiability Testing (SAT 2022)

Abstract
We advance the theory of QBF proof systems by showing the first simulation of the universal checking format QRAT by a theory-friendly system. We show that the sequent system G fully p-simulates QRAT, including the Extended Universal Reduction (EUR) rule which was recently used to show QRAT does not have strategy extraction. Because EUR heavily uses resolution paths our technique also brings resolution path dependency and sequent systems closer together. While we do not recommend G for practical applications this work can potentially show what features are needed for a new QBF checking format stronger than QRAT.
Cite as

Leroy Chew and Marijn J. H. Heule. Relating Existing Powerful Proof Systems for QBF. In 25th International Conference on Theory and Applications of Satisfiability Testing (SAT 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 236, pp. 10:1-10:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{chew_et_al:LIPIcs.SAT.2022.10,
  author =	{Chew, Leroy and Heule, Marijn J. H.},
  title =	{{Relating Existing Powerful Proof Systems for QBF}},
  booktitle =	{25th International Conference on Theory and Applications of Satisfiability Testing (SAT 2022)},
  pages =	{10:1--10:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-242-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{236},
  editor =	{Meel, Kuldeep S. and Strichman, Ofer},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.SAT.2022.10},
  URN =		{urn:nbn:de:0030-drops-166845},
  doi =		{10.4230/LIPIcs.SAT.2022.10},
  annote =	{Keywords: QBF, Proof Complexity, Verification, Strategy Extraction, Sequent Calculus}
}
Document
DOI: 10.4230/LIPIcs.STACS.2022.22
Towards Uniform Certification in QBF

Authors: Leroy Chew and Friedrich Slivovsky

Published in: LIPIcs, Volume 219, 39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022)

Abstract
We pioneer a new technique that allows us to prove a multitude of previously open simulations in QBF proof complexity. In particular, we show that extended QBF Frege p-simulates clausal proof systems such as IR-Calculus, IRM-Calculus, Long-Distance Q-Resolution, and Merge Resolution. These results are obtained by taking a technique of Beyersdorff et al. (JACM 2020) that turns strategy extraction into simulation and combining it with new local strategy extraction arguments. This approach leads to simulations that are carried out mainly in propositional logic, with minimal use of the QBF rules. Our proofs therefore provide a new, largely propositional interpretation of the simulated systems. We argue that these results strengthen the case for uniform certification in QBF solving, since many QBF proof systems now fall into place underneath extended QBF Frege.
Cite as

Leroy Chew and Friedrich Slivovsky. Towards Uniform Certification in QBF. In 39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 219, pp. 22:1-22:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{chew_et_al:LIPIcs.STACS.2022.22,
  author =	{Chew, Leroy and Slivovsky, Friedrich},
  title =	{{Towards Uniform Certification in QBF}},
  booktitle =	{39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022)},
  pages =	{22:1--22:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-222-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{219},
  editor =	{Berenbrink, Petra and Monmege, Benjamin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2022.22},
  URN =		{urn:nbn:de:0030-drops-158326},
  doi =		{10.4230/LIPIcs.STACS.2022.22},
  annote =	{Keywords: QBF, Proof Complexity, Verification, Frege, Extended Frege, Strategy Extraction}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2016.40
Understanding Cutting Planes for QBFs

Authors: Olaf Beyersdorff, Leroy Chew, Meena Mahajan, and Anil Shukla

Published in: LIPIcs, Volume 65, 36th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2016)

Abstract
We define a cutting planes system CP+ForallRed for quantified Boolean formulas (QBF) and analyse the proof-theoretic strength of this new calculus. While in the propositional case, Cutting Planes is of intermediate strength between resolution and Frege, our findings here show that the situation in QBF is slightly more complex: while CP+ForallRed is again weaker than QBF Frege and stronger than the CDCL-based QBF resolution systems Q-Res and QU-Res, it turns out to be incomparable to even the weakest expansion-based QBF resolution system ForallExp+Res. Technically, our results establish the effectiveness of two lower bound techniques for CP+ForallRed: via strategy extraction and via monotone feasible interpolation.
Cite as

Olaf Beyersdorff, Leroy Chew, Meena Mahajan, and Anil Shukla. Understanding Cutting Planes for QBFs. In 36th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 65, pp. 40:1-40:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{beyersdorff_et_al:LIPIcs.FSTTCS.2016.40,
  author =	{Beyersdorff, Olaf and Chew, Leroy and Mahajan, Meena and Shukla, Anil},
  title =	{{Understanding Cutting Planes for QBFs}},
  booktitle =	{36th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2016)},
  pages =	{40:1--40:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-027-9},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{65},
  editor =	{Lal, Akash and Akshay, S. and Saurabh, Saket and Sen, Sandeep},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2016.40},
  URN =		{urn:nbn:de:0030-drops-68758},
  doi =		{10.4230/LIPIcs.FSTTCS.2016.40},
  annote =	{Keywords: proof complexity, QBF, cutting planes, resolution, simulations}
}
Document
DOI: 10.4230/LIPIcs.STACS.2016.15
Are Short Proofs Narrow? QBF Resolution is not Simple

Authors: Olaf Beyersdorff, Leroy Chew, Meena Mahajan, and Anil Shukla

Published in: LIPIcs, Volume 47, 33rd Symposium on Theoretical Aspects of Computer Science (STACS 2016)

Abstract
The groundbreaking paper 'Short proofs are narrow - resolution made simple' by Ben-Sasson and Wigderson (J. ACM 2001) introduces what is today arguably the main technique to obtain resolution lower bounds: to show a lower bound for the width of proofs. Another important measure for resolution is space, and in their fundamental work, Atserias and Dalmau (J. Comput. Syst. Sci. 2008) show that space lower bounds again can be obtained via width lower bounds. Here we assess whether similar techniques are effective for resolution calculi for quantified Boolean formulas (QBF). A mixed picture emerges. Our main results show that both the relations between size and width as well as between space and width drastically fail in Q-resolution, even in its weaker tree-like version. On the other hand, we obtain positive results for the expansion-based resolution systems Forall-Exp+Res and IR-calc, however only in the weak tree-like models. Technically, our negative results rely on showing width lower bounds together with simultaneous upper bounds for size and space. For our positive results we exhibit space and width-preserving simulations between QBF resolution calculi.
Cite as

Olaf Beyersdorff, Leroy Chew, Meena Mahajan, and Anil Shukla. Are Short Proofs Narrow? QBF Resolution is not Simple. In 33rd Symposium on Theoretical Aspects of Computer Science (STACS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 47, pp. 15:1-15:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{beyersdorff_et_al:LIPIcs.STACS.2016.15,
  author =	{Beyersdorff, Olaf and Chew, Leroy and Mahajan, Meena and Shukla, Anil},
  title =	{{Are Short Proofs Narrow? QBF Resolution is not Simple}},
  booktitle =	{33rd Symposium on Theoretical Aspects of Computer Science (STACS 2016)},
  pages =	{15:1--15:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-001-9},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{47},
  editor =	{Ollinger, Nicolas and Vollmer, Heribert},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2016.15},
  URN =		{urn:nbn:de:0030-drops-57164},
  doi =		{10.4230/LIPIcs.STACS.2016.15},
  annote =	{Keywords: proof complexity, QBF, resolution, lower bound techniques, simulations}
}
Document
DOI: 10.4230/LIPIcs.STACS.2015.76
Proof Complexity of Resolution-based QBF Calculi

Authors: Olaf Beyersdorff, Leroy Chew, and Mikolás Janota

Published in: LIPIcs, Volume 30, 32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015)

Abstract
Proof systems for quantified Boolean formulas (QBFs) provide a theoretical underpinning for the performance of important QBF solvers. However, the proof complexity of these proof systems is currently not well understood and in particular lower bound techniques are missing. In this paper we exhibit a new and elegant proof technique for showing lower bounds in QBF proof systems based on strategy extraction. This technique provides a direct transfer of circuit lower bounds to lengths of proofs lower bounds. We use our method to show the hardness of a natural class of parity formulas for Q-resolution and universal Q-resolution. Variants of the formulas are hard for even stronger systems as long-distance Q-resolution and extensions. With a completely different lower bound argument we show the hardness of the prominent formulas of Kleine Büning et al. [34] for the strong expansion-based calculus IR-calc. Our lower bounds imply new exponential separations between two different types of resolution-based QBF calculi: proof systems for CDCL-based solvers (Q-resolution, long-distance Q-resolution) and proof systems for expansion-based solvers (forallExp+Res and its generalizations IR-calc and IRM-calc). The relations between proof systems from the two different classes were not known before.
Cite as

Olaf Beyersdorff, Leroy Chew, and Mikolás Janota. Proof Complexity of Resolution-based QBF Calculi. In 32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 30, pp. 76-89, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{beyersdorff_et_al:LIPIcs.STACS.2015.76,
  author =	{Beyersdorff, Olaf and Chew, Leroy and Janota, Mikol\'{a}s},
  title =	{{Proof Complexity of Resolution-based QBF Calculi}},
  booktitle =	{32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015)},
  pages =	{76--89},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-78-1},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{30},
  editor =	{Mayr, Ernst W. and Ollinger, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2015.76},
  URN =		{urn:nbn:de:0030-drops-49057},
  doi =		{10.4230/LIPIcs.STACS.2015.76},
  annote =	{Keywords: proof complexity, QBF, lower bound techniques, separations}
}
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