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Solving and Verifying the Boolean Pythagorean Triples Problem via Cube-and-Conquer

  • Marijn J. H. Heule
  • Oliver Kullmann
  • Victor W. Marek
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9710)

Abstract

The boolean Pythagorean Triples problem has been a longstanding open problem in Ramsey Theory: Can the set \(\mathbb {N}= \{1,2,\dots \}\) of natural numbers be divided into two parts, such that no part contains a triple (abc) with \(a^2 + b^2 = c^2\) ? A prize for the solution was offered by Ronald Graham over two decades ago. We solve this problem, proving in fact the impossibility, by using the Cube-and-Conquer paradigm, a hybrid SAT method for hard problems, employing both look-ahead and CDCL solvers. An important role is played by dedicated look-ahead heuristics, which indeed allowed to solve the problem on a cluster with 800 cores in about 2 days. Due to the general interest in this mathematical problem, our result requires a formal proof. Exploiting recent progress in unsatisfiability proofs of SAT solvers, we produced and verified a proof in the DRAT format, which is almost 200 terabytes in size. From this we extracted and made available a compressed certificate of 68 gigabytes, that allows anyone to reconstruct the DRAT proof for checking.

Keywords

Satisfying Assignment Unit Clause Empty Clause Resolution Proof Ramsey Theory 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgements

The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing grid resources that have contributed to the research results reported within this paper.

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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  • Marijn J. H. Heule
    • 1
  • Oliver Kullmann
    • 2
  • Victor W. Marek
    • 3
  1. 1.The University of Texas at AustinAustinUSA
  2. 2.Swansea UniversitySwanseaUK
  3. 3.University of KentuckyLexingtonUSA

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