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DOI: 10.4230/LIPIcs.ITP.2024.16

A Formal Proof of R(4,5)=25

Authors: Thibault Gauthier and Chad E. Brown

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract

In 1995, McKay and Radziszowski proved that the Ramsey number R(4,5) is equal to 25. Their proof relies on a combination of high-level arguments and computational steps. The authors have performed the computational parts of the proof with different implementations in order to reduce the possibility of an error in their programs. In this work, we prove this theorem in the interactive theorem prover HOL4 limiting the uncertainty to the small HOL4 kernel. Instead of verifying their algorithms directly, we rely on the HOL4 interface to MiniSat to prove gluing lemmas. To reduce the number of such lemmas and thus make the computational part of the proof feasible, we implement a generalization algorithm. We verify that its output covers all the possible cases by implementing a custom SAT-solver extended with a graph isomorphism checker.

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Thibault Gauthier and Chad E. Brown. A Formal Proof of R(4,5)=25. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 16:1-16:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gauthier_et_al:LIPIcs.ITP.2024.16,
  author =	{Gauthier, Thibault and Brown, Chad E.},
  title =	{{A Formal Proof of R(4,5)=25}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{16:1--16:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.16},
  URN =		{urn:nbn:de:0030-drops-207446},
  doi =		{10.4230/LIPIcs.ITP.2024.16},
  annote =	{Keywords: Ramsey numbers, SAT solvers, symmetry breaking, generalization, HOL4}
}

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DOI: 10.4230/OASIcs.FMBC.2022.4

Proofgold: Blockchain for Formal Methods

Authors: Chad E. Brown, Cezary Kaliszyk, Thibault Gauthier, and Josef Urban

Published in: OASIcs, Volume 105, 4th International Workshop on Formal Methods for Blockchains (FMBC 2022)

Abstract

Proofgold is a peer to peer cryptocurrency making use of formal logic. Users can publish theories and then develop a theory by publishing documents with definitions, conjectures and proofs. The blockchain records the theories and their state of development (e.g., which theorems have been proven and when). Two of the main theories are a form of classical set theory (for formalizing mathematics) and an intuitionistic theory of higher-order abstract syntax (for reasoning about syntax with binders). We have also significantly modified the open source Proofgold Core client software to create a faster, more stable and more efficient client, Proofgold Lava. Two important changes are the cryptography code and the database code, and we discuss these improvements. We also discuss how the Proofgold network can be used to support large formalization efforts.

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Chad E. Brown, Cezary Kaliszyk, Thibault Gauthier, and Josef Urban. Proofgold: Blockchain for Formal Methods. In 4th International Workshop on Formal Methods for Blockchains (FMBC 2022). Open Access Series in Informatics (OASIcs), Volume 105, pp. 4:1-4:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{brown_et_al:OASIcs.FMBC.2022.4,
  author =	{Brown, Chad E. and Kaliszyk, Cezary and Gauthier, Thibault and Urban, Josef},
  title =	{{Proofgold: Blockchain for Formal Methods}},
  booktitle =	{4th International Workshop on Formal Methods for Blockchains (FMBC 2022)},
  pages =	{4:1--4:15},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-250-1},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{105},
  editor =	{Dargaye, Zaynah and Schneidewind, Clara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2022.4},
  URN =		{urn:nbn:de:0030-drops-171851},
  doi =		{10.4230/OASIcs.FMBC.2022.4},
  annote =	{Keywords: Formal logic, Blockchain, Proofgold}
}

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Documents authored by Gauthier, Thibault

A Formal Proof of R(4,5)=25

Abstract

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Proofgold: Blockchain for Formal Methods

Abstract

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