Minimum star discrepancy in the unit square
Also known asstar discrepancyminimum star discrepancylow-discrepancy point set
Place n points in the unit square [0, 1]². For every origin-anchored half-open rectangle [0, u) × [0, v), compare the fraction of points inside the box with its area uv, and minimize the supremum discrepancy D* over all such rectangles.
Formal definition
- ContainerThe unit square [0, 1]², with lower-left corner at (0, 0) and upper-right corner at (1, 1)
- SubmissionExactly n distinct points, each coordinate written as a decimal string with at most nine decimal places
- RectanglesTest rectangles are half-open boxes [0, u) × [0, v) with (u, v) ∈ [0, 1]²; points on the top or right boundary count as outside
- Star discrepancyThe indicator 𝟙 is 1 when the point lies in [0, u) × [0, v) and 0 otherwise; D*(P) is the supremum absolute difference between the point fraction and the area uv
- ObjectiveMinimize D*(P) over all valid point sets P. The verifier evaluates the open and closed one-sided limits on the grid induced by the submitted coordinates and compares exact integers
Getting a feel for it
Spreading points evenly
If a rectangle covers 30% of the square, ideally it should contain 30% of the points on average. This problem checks every origin-anchored rectangle and scores the worst mismatch, so the goal is to distribute the points as evenly as possible across all prefix rectangles.
Why regular grids lose
The rules allow multiple points in the same row or column, but doing so hurts the score: if several points share an x-coordinate, the moment a rectangle's right edge crosses it, those points all enter the box at once, causing a jump in the point fraction while the area grows continuously. Good configurations stagger both coordinates so no two points share a coordinate.
Known results
Optimal point sets for n ≤ 21 were proven by Clément, Doerr, Klamroth, and Paquete in 2025 (Proc. Amer. Math. Soc. Ser. B 12: 78–90). This problem therefore starts at n = 22, and every instance from n = 22 upward remains open.
Current best solutions by n
Each parameter n is an independently scored sub-problem. Select any card to inspect the current record construction or submit a stronger solution.
Discussion (1) ↓Data and citation
All sub-problems in this family — authoritative scores, proof status, coordinates, and sources — are published at the stable URL below under CC BY 4.0. Because scores update as records fall, please cite the file's generatedAt timestamp.
GET https://minmaxarena.com/data/star-discrepancy.json
Cite the frozen 2026-10 edition: live records change, whereas a frozen edition stays fixed and reproducible.
GET https://minmaxarena.com/data/editions/2026-10/star-discrepancy.json
BibTeX (click to copy)
@misc{minmaxarena-star-discrepancy-2026-10,
title = {{Minimum star discrepancy in the unit square} (P54)},
author = {{MinMax Arena}},
year = {2026},
note = {Machine-verified records, 2026-10 edition},
url = {https://minmaxarena.com/data/editions/2026-10/star-discrepancy.json},
license = {CC BY 4.0}
}Discussion
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