REVIEW 1 major objections 4 minor 28 references
Automated Symmetric Constructions in Discrete Geometry
T0 review · 1 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read This paper proves that the smallest odd-sized everywhere-unbalanced point set has 21 points, and that symmetric 16-point hexagon-free sets need 4-fold or 5-fold symmetry.
desk verdict The positive constructions are real, but the encoding as written cannot produce the paper's own collinear witness, so the minimality claims are unsupported. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing device is a set of dynamic point-ordering axioms for the orientation variables, which record for each triple of points whether the triple is oriented clockwise or counterclockwise. Earlier signotope encodings require a fixed left-to-right order of the points, incompatible with rotational symmetry; here the solver itself chooses a linear order through dedicated ordering variables, and the signotope-style clauses are applied relative to that chosen order. Together with the basic CC-system axioms, these clauses are shown to imply the full CC axioms, with the proof reduced to the five-point case. A separate family of collinearity axioms then forces consistent orientations when three points lie on one line, which is essential for the everywhere-unbalanced problem because its configurations necessarily contain collinearities. Symmetry is imposed by merging every orbit of orientation variables under the rotation into a single representative, and redundant constraints are removed orbit by orbit. A purpose-built local-search solver, called Localizer, turns the abstract orientation assignments into explicit coordinates for general-position sets, while the collinear cases are realized by extracting abstract lines and tuning the remaining free coordinates with a numerical global optimizer.
What would settle it
Exhibit a 2-everywhere-unbalanced set with 19 points, with explicit rational coordinates and every pair-line verified to have imbalance at least 2, or exhibit a realizable 3-fold symmetric 16-point set with no convex 6-gon; either would contradict one of the paper's refutation claims.
Extended reading notes
Core claim
On the paper's own terms, the central discovery is twofold. For everywhere-unbalanced points, the previously known 12-point configuration is shown to be the minimum possible size for imbalance 2, and the odd case is settled exactly: no 2-everywhere-unbalanced set with 19 or fewer points exists, while a 3-fold combinatorially symmetric 21-point construction, given by explicit coordinates, does, so 21 is the minimal odd size. For the Erdős–Szekeres problem, the paper finds 16-point general-position sets without a convex 6-gon that are 4-fold and 5-fold rotationally symmetric, enumerates all symmetry-normalized solutions (66 for 4-fold and 948 for 5-fold, with 18 and 92 realizable, respectively), and proves that no 3-fold symmetric such set exists. It also reports that among the 310,187,713 non-isomorphic SAT solutions for a 4-fold symmetric 32-point set without a convex 7-gon, the inner 12 points always form one of six configurations, none realizable, so no realizable 4-fold symmetric 32-point 7-gon-free set exists.
Load-bearing premise
The refutation claims depend on the new ordering rules and collinearity rules never accidentally ruling out a real configuration, and on the SAT solver being right when it reports that no solution exists, since those reports come without independently checkable certificates; the existence claims are coordinate-verified and do not share this risk.
Editorial extensions
If this is right
- The even minimum for imbalance 2 is now known to be 12 points, and the odd minimum is 21 points.
- The 4-fold and 5-fold 16-point hexagon-free sets give structured, human-readable witnesses that 16 points can avoid a convex 6-gon, alongside the older asymmetric construction.
- The dynamic-ordering axioms remove the need for a fixed left-to-right point order, so the same SAT approach can impose rotational symmetry in other discrete-geometry searches.
- For the 32-point 7-gon-free case, the enumeration shows every symmetry-normalized SAT solution fails realization at its inner 12 points, so the non-existence is not an artifact of incomplete search.
- The 21-point and 16-point existence constructions come with explicit coordinates, so they can be verified directly without relying on the SAT pipeline.
Reading between the lines
- The same symmetry-aware pipeline is a natural first attack on 3-everywhere-unbalanced sets: impose a rotational ansatz, solve the abstract design, then search for coordinates.
- The enumeration data suggest a cheap realizability pre-filter: among symmetric hexagon-free solutions, high counts of convex quadrilaterals and low counts of convex pentagons make realization more likely, so a future pipeline could score solutions before spending time on realization.
- If the observed tendency for small extremal constructions to admit symmetry continues, proving symmetric constructions for every parameter value at least 7 could give a structured route toward the conjectured Erdős–Szekeres bound.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents a computational pipeline for discovering rotationally symmetric point sets in discrete geometry. It introduces dynamic-ordering axioms that replace the left-to-right ordering of previous signotope encodings, a symmetry-reduction scheme that unifies equivalent orientation variables, and a local-search realizability solver called Localizer. The methodology is applied to two problems: the Erdős–Szekeres problem, for which the authors report 4-fold and 5-fold symmetric 16-point sets with no convex 6-gon and a classification of all realizable such configurations (9 and 46 non-isomorphic examples), and the everywhere-unbalanced-points problem, for which they report a 21-point 2-everywhere-unbalanced configuration and claim it is the minimal odd-sized solution, while also claiming Alon's 12-point construction is the minimal even-sized solution. Explicit coordinates for the main constructions are given in Appendix C, and the code is publicly available.
Significance. If the minimality results were established, the paper would settle the minimal even and odd sizes for 2-everywhere-unbalanced point sets and would introduce a broadly applicable method for embedding rotational symmetry into SAT encodings of geometric problems. The explicit coordinate lists for the 21-point construction and for the 16-point 4-fold and 5-fold no-hexagon configurations are concrete, checkable contributions, and the public release of Localizer with its reported performance is a useful engineering asset. The symmetry reduction via variable unification is a genuinely interesting technique. However, the non-existence and minimality claims rest on UNSAT answers from an encoding whose published description is inconsistent with the paper's own witness, so the headline claims are not currently supported.
major comments (1)
- [Section 4.1, Eq. (4); Section 4.2; Appendix C, Table 3] Section 6.2: the conclusion "there does not exist a realizable 4-fold symmetry on 32 points without a 7-gon" is stronger than the evidence described. The footnote explicitly states that the realizer tool "can only determine realizability, not unrealizability," and that for "several" configurations the authors found known unrealizable 10-point subsets. To conclude non-existence for all six inner-12 configurations, the paper must provide a proof of unrealizability for each of those configurations (e.g., an explicit unrealizable subset together with a citation or a formal proof), not merely report that Localizer failed to find a realization.
minor comments (4)
- [Appendix D, Proof of Proposition 2] The proof of Proposition 2 concludes by stating that a SAT solver reported Ψ to be unsatisfiable, but no certificate is provided. Since this is a foundational lemma for the completeness of the dynamic-ordering axioms, please include a DRAT certificate or a reproducible script with the exact solver version and parameters.
- [Section 5.2] The ad-hoc method for realizing collinear configurations is described only at a high level. The extraction of "abstract lines" from τ, the determination of dependent points, and the exact objective used in the differential_evolution step should be specified so that the coordinates in Table 3 can be independently verified without using the authors' code.
- [Section 3.2] The sentence "we can assume without loss of generality that all points whose index is 1 mod 5 are in the bottom-left quadrant" appears in the 4-fold symmetry subsection and seems to be a typo for "1 mod 4"; please correct it.
- [Throughout] The manuscript contains numerous missing spaces and typos (e.g., "DR-complete" for ∃R-complete, "MackBook", "weuse", "theset"). A careful proofreading pass is needed.
Circularity Check
No significant circularity: coordinate-verified constructions and an imposed symmetry ansatz make the central existence results independent; self-citations are non-load-bearing, while the EU encoding consistency issue is a soundness concern, not a circular reduction.
full rationale
The paper's central existence claims are not circular. The 16-point 4-fold and 5-fold Erdős–Szekeres constructions are verified by explicit coordinate tables (Appendix C, Tables 1 and 2), and the 21-point 2-EU construction is likewise supported by explicit coordinates (Table 3). These results do not derive the target statement from itself; they exhibit a concrete witness. The imposed rotational symmetry is an ansatz constraint built into the SAT encoding, not a parameter fitted to the answer, so the symmetric solutions are not predictions-by-construction. The minimality and nonexistence claims (12-point minimal even, no odd 2-EU set with at most 19 points, no 3-fold 16-point hexagon-free configuration) are UNSAT results, and their validity depends on whether the SAT axioms faithfully capture all geometric configurations. That is a soundness question, not a circularity question. However, as a flagged manuscript-level concern: Section 4.1's dynamic-ordering axiom (4) is proved only for general position, while Section 4.2 states that collinearity axioms are added 'in addition to the axioms in Section 4.1'; as written, a collinear quadruple would falsify axiom (4) under any total order, and Table 3's witness contains five collinear points, so the exact axiom set used for the EU UNSAT refutations is under-specified in the text. This deserves correction or clarification, but it is not a reduction of the geometric conclusion to its own premise. The self-citations ([13], [21], [22]) are motivational, comparative, or machine-checked formalization and are not load-bearing; the Lean formalization in [22] is independent support. Overall, the derivation chain is not circular.
Assumptions & free parameters
free parameters (1)
- Localizer search hyperparameters
assumptions (5)
- domain assumption Any finite point set with distinct x-coordinates satisfies the dynamic-ordering axioms from Equations 4 and 5.
- domain assumption The collinearity axioms in Section 4.2 are satisfied by every real collinear configuration.
- domain assumption The SAT solver, CaDiCaL with all-solution enumeration, returns correct UNSAT answers.
- ad hoc to paper The inner 12-point configurations in Section 6.2 are unrealizable, as claimed from the realizer's failure and known unrealizable subsets.
- standard math Carathéodory's theorem in the plane: a set in general position is in convex position if and only if every 4-point subset is in convex position.
Cite this review
Pith. "Pith review of Automated Symmetric Constructions in Discrete Geometry." pith.science (2026). https://pith.science/paper/5FNE57G7
@misc{pith2026250600224,
author = {Pith},
title = {Pith review of: Automated Symmetric Constructions in Discrete Geometry},
year = {2026},
howpublished = {\url{https://pith.science/paper/5FNE57G7}},
note = {Machine review of arXiv:2506.00224}
}
abstract
We present a computational methodology for obtaining rotationally symmetric sets of points satisfying discrete geometric constraints, and demonstrate its applicability by discovering new solutions to some well-known problems in combinatorial geometry. Our approach takes the usage of SAT solvers in discrete geometry further by directly embedding rotational symmetry into the combinatorial encoding of geometric configurations. Then, to realize concrete point sets corresponding to abstract designs provided by a SAT solver, we introduce a novel local-search realizability solver, which shows excellent practical performance despite the intrinsic $\exists \mathbb{R}$-completeness of the problem. Leveraging this combined approach, we provide symmetric extremal solutions to the Erd\H{o}s-Szekeres problem, as well as a minimal odd-sized solution with 21 points for the everywhere-unbalanced-points problem, improving on the previously known 23-point configuration. The imposed symmetries yield more aesthetically appealing solutions, enhancing human interpretability, and simultaneously offer computational benefits by significantly reducing the number of variables required to encode discrete geometric problems.
Figures
Figures from the paper (4 more)
Reference graph
Works this paper leans on
-
[1]
Order,19(3):265–281,September2002
OswinAichholzer,FranzAurenhammer,andHannesKrasser.EnumeratingOrderTypesforSmallPoint SetswithApplications. Order,19(3):265–281,September2002
-
[2]
Kleitman and Combinatorics: A Celebration,257(2):599–624,November2002
NogaAlon.Researchproblems. Kleitman and Combinatorics: A Celebration,257(2):599–624,November2002
-
[3]
ArminBiere,TobiasFaller,KatalinFazekas,MathiasFleury,NilsFroleyks,andFlorianPollitt.CaDiCaL2.0. InArieGurfinkelandVijayGanesh,editors, Computer Aided Verification - 36th International Conference, CAV 2024, Montreal, QC, Canada, July 24-27, 2024, Proceedings, Part I,volume14681of Lecture Notes in Computer Science,pages133–152.Springer,2024
work page 2024
-
[4]
DavidConlonandJeckLim.Everywhereunbalancedconfigurations,2025
work page 2025
-
[5]
DiscreteAppliedMathematics ,109(1):67– 94,April2001
StefanFelsnerandHelmutWeil.Sweeps,arrangementsandsignotopes. DiscreteAppliedMathematics ,109(1):67– 94,April2001
-
[6]
From summetria to symmetry: The making of a revolutionary scientific concept
GioraandBernardRGoldstein. From summetria to symmetry: The making of a revolutionary scientific concept. Archimedes: NewStudiesintheHistoryandPhilosophyofScienceandTechnology.Springer,NewYork, NY,2008edition,July2008
-
[7]
Marijn Heule and Toby Walsh. Symmetry in Solutions.Proceedings of the AAAI Conference on Artificial Intelligence,24(1):77–82,July2010
-
[8]
Journal of Combinatorics,8(3):391–422,June 2017
MarijnJ.H.Heule.Avoidingtriplesinarithmeticprogression. Journal of Combinatorics,8(3):391–422,June 2017
work page 2017
Show all 28 references
-
[9]
Marijn J. H. Heule. Schur number five. InProceedings of the Thirty-Second AAAI Conference on Artificial IntelligenceandThirtiethInnovativeApplicationsofArtificialIntelligenceConferenceandEighthAAAISymposium on Educational Advances in Artificial Intelligence,AAAI’18/IAAI’18/EAAI’18...
-
[10]
In Bernd Finkbeiner and Laura Kovács, editors,Tools and Algorithms for the Construction and Analysis of Systems,pages61–80,Cham,2024.SpringerNatureSwitzerland
MarijnJ.H.HeuleandManfredScheucher.HappyEnding: AnEmptyHexagoninEverySetof30Points. In Bernd Finkbeiner and Laura Kovács, editors,Tools and Algorithms for the Construction and Analysis of Systems,pages61–80,Cham,2024.SpringerNatureSwitzerland
2024
-
[11]
AUTOMATED SYMMETRIC CONSTRUCTIONS IN DISCRETE GEOMETRY 15
DonaldE.Knuth.AxiomsandHulls.InDonaldE.Knuth,editor, AxiomsandHulls ,LectureNotesinComputer Science,pages1–98.Springer,Berlin,Heidelberg,1992. AUTOMATED SYMMETRIC CONSTRUCTIONS IN DISCRETE GEOMETRY 15
1992
-
[12]
Extremalproblemsincombinatorialgeometry .Lecturenotesseries.AarhusUniversitet, MatematiskInstitut,1979
YakovShimeonKupitz. Extremalproblemsincombinatorialgeometry .Lecturenotesseries.AarhusUniversitet, MatematiskInstitut,1979
1979
-
[13]
Master’sthesis,CarnegieMellonUniversity,2025
EthanMackey.Pinwheelsandpolygons: Symmetricrealizationsofpolygon-freepointplacementsviasat. Master’sthesis,CarnegieMellonUniversity,2025
2025
-
[14]
Bulletin of the American Mathematical Society,37(4):437–458,2000
W.MorrisandV.Soltan.TheErdos-Szekeresproblemonpointsinconvexposition–asurvey. Bulletin of the American Mathematical Society,37(4):437–458,2000
2000
-
[15]
SIGPLAN Not.,17(9):7–13,September1982
AlanJ.Perlis.Specialfeature: Epigramsonprogramming. SIGPLAN Not.,17(9):7–13,September1982
-
[16]
Discrete & Computational Geometry,30(3):415–435, September2003
RomPinchasi.LinesWithManyPointsOnBothSides. Discrete & Computational Geometry,30(3):415–435, September2003
-
[17]
Gansner,editors, Graph Drawing,pages334–344,Berlin,Heidelberg,2010.Springer
MarcusSchaefer.ComplexityofSomeGeometricandTopologicalProblems.InDavidEppsteinandEmdenR. Gansner,editors, Graph Drawing,pages334–344,Berlin,Heidelberg,2010.Springer
2010
-
[18]
Computational Geometry,91:101670,2020
ManfredScheucher.Twodisjoint5-holesinpointsets. Computational Geometry,91:101670,2020
2020
-
[19]
Computing in Geometry and Topology,2(1):2:1–2:13,March2023
ManfredScheucher.ASATAttackonErdős-SzekeresNumbersinR^dandtheEmptyHexagonTheorem. Computing in Geometry and Topology,2(1):2:1–2:13,March2023
-
[20]
Towards an optimal CNF encoding of boolean cardinality constraints
Carsten Sinz. Towards an optimal CNF encoding of boolean cardinality constraints. In Peter van Beek, editor,Principles and Practice of Constraint Programming - CP 2005, 11th International Conference, CP 2005, Sitges, Spain, October 1-5, 2005, Proceedings,volume3709of Lecture N...
2005
-
[21]
BernardoSubercaseaux,JohnMackey,MarijnJ.H.Heule,andRubenMartins.Automatedmathematical discoveryandverification: Minimizingpentagonsintheplane,2024
2024
-
[22]
BernardoSubercaseaux,WojciechNawrocki,JamesGallicchio,CaydenCodel,MarioCarneiro,andMarijn J.H.Heule.FormalVerificationoftheEmptyHexagonNumber.InYvesBertot,TemurKutsia,andMichael Norrish, editors,15th International Conference on Interactive Theorem Proving (ITP 2024), volume 309...
2024
-
[23]
Computer solution to the 17-point Erdős-Szekeres problem.The ANZIAM Journal,48(2):151–164,2006
George Szekeres and Lindsay Peters. Computer solution to the 17-point Erdős-Szekeres problem.The ANZIAM Journal,48(2):151–164,2006
2006
-
[24]
Handbook of Discrete and Computational Geometry.ChapmanandHall/CRC,NewYork,3edition,November2017
CsabaD.Toth,JosephO’Rourke,andJacobE.Goodman,editors. Handbook of Discrete and Computational Geometry.ChapmanandHall/CRC,NewYork,3edition,November2017
-
[25]
Nature Methods,17:261–272,2020
PauliVirtanen,RalfGommers,TravisE.Oliphant,MattHaberland,TylerReddy,DavidCournapeau,Evgeni Burovski,PearuPeterson,WarrenWeckesser,JonathanBright,StéfanJ.vanderWalt,MatthewBrett,Joshua Wilson,K.JarrodMillman,NikolayMayorov,AndrewR.J.Nelson,EricJones,RobertKern,EricLarson,CJ Car...
2020
-
[26]
TobyWalsh.SymmetrywithinandbetweenSolutions.InByoung-TakZhangandMehmetA.Orgun,editors, PRICAI 2010: Trends in Artificial Intelligence,pages11–13,Berlin,Heidelberg,2010.Springer
2010
-
[27]
Symmetry.PrincetonScienceLibrary.PrincetonUniversityPress,Princeton,NJ,December 2016
HermannWeyl. Symmetry.PrincetonScienceLibrary.PrincetonUniversityPress,Princeton,NJ,December 2016
2016
-
[28]
php?title=Happy%20ending%20problem&oldid=1282669476,2025.[Online;accessed12-May-2025]
Wikipedia.Happyendingproblem—Wikipedia,thefreeencyclopedia.http://en.wikipedia.org/w/index. php?title=Happy%20ending%20problem&oldid=1282669476,2025.[Online;accessed12-May-2025]. AppendixA. Realizationsof4-FoldSymmetricConfigurations Below are the nine non-isomorphic realizable...
2025
Reviewed August 7, 2026 · model on record in the stance chip above.
Discussion (0). Sign in to comment.