P55 · Extremal configurations · Classic · Applied frontier · Weak baseline

Optimal quantization in the unit square

Also known asoptimal quantizationquantizer problemcentroidal Voronoi tessellation

1y0
0x1
VERIFIED CONSTRUCTION12 Voronoi cells; the costliest cell accounts for 10.7% of total cost
n = 12Current record · open

Place n points in the unit square. Each location in the square is assigned to its nearest point; minimize the average squared distance over the square from a location to its assigned point.

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
  • AssignmentEvery location belongs to its nearest submitted point (the Voronoi partition); equidistant boundaries have measure zero and do not affect the integral
  • ScoreE(P) is the integral over the unit square of the squared distance to the nearest submitted point (equal to the mean since the square has area 1); the verifier computes the exact rational integral and rounds upward at 10⁻¹⁸E(P)=∫∫mini‖x−pi‖2dx
  • ObjectiveMinimize E(P) over all valid point sets PminPE(P)

Getting a feel for it

An analogy: respawn points

Think of the square as a map and the n points as respawn points. A player appears uniformly at random on the map and is sent to the nearest respawn point; the score is the mean squared length of that trip.

Why Lloyd's algorithm alone is not enough

Repeatedly moving each point to the centroid of its Voronoi cell is Lloyd's algorithm. The iteration converges to a centroidal Voronoi tessellation, but the quantization energy has many local minima with different cell topologies, so finding the global optimum requires searching across distinct basins.

Known results

Exact optima are proven for n ≤ 2, while published results for n = 3, 4, and 5 rely on an unproven symmetry assumption (Roychowdhury, arXiv:1608.03815), and all cases with n ≥ 6 remain open. Fejes Tóth's moment theorem provides the universal strict lower bound 5/(18√3·n), corresponding to regular hexagonal cells that cannot tile a square.

ONE LEADERBOARD PER n

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 (0) ↓
n6
CURRENT RECORD0.029951010800596
Easy
Answer sourceMinMax Arena
Solution methodMinMax Arena offline search
n7
CURRENT RECORD0.025322688865706
Easy
Answer sourceMinMax Arena
Solution methodMinMax Arena offline search
n8
CURRENT RECORD0.021359097994371
Medium
Record holderSigmoid with Codex
Solution methodAI · OpenAI: GPT-5.6 Sol
n9
CURRENT RECORD0.018518518518519
Easy
Answer sourceMinMax Arena
Solution methodMinMax Arena offline search
n10
CURRENT RECORD0.016992964760621
Easy
Answer sourceMinMax Arena
Solution methodMinMax Arena offline search
n11
CURRENT RECORD0.015553138716519
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n12
CURRENT RECORD0.014205377583046
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n13
CURRENT RECORD0.013164793813830
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n14
CURRENT RECORD0.012073292022843
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n15
CURRENT RECORD0.011168368317443
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n16
CURRENT RECORD0.010394191513670
Medium
Record holderGaozx1
Solution methodAI · Z.ai: GLM 5.3 Flash
n17
CURRENT RECORD0.009868422277524
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n18
CURRENT RECORD0.009349882612349
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n19
CURRENT RECORD0.008851717018979
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n20
CURRENT RECORD0.008384274285159
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n21
CURRENT RECORD0.007976706012785
Medium
Record holder邱仲普
Solution methodAI · MoonshotAI: Kimi K3
n22
CURRENT RECORD0.007592688758999
Medium
Record holder邱仲普
Solution methodAI · MoonshotAI: Kimi K3
n23
CURRENT RECORD0.007218156525266
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n24
CURRENT RECORD0.006921404507186
Medium
Record holderSigmoid with Codex
Solution methodAI · OpenAI: GPT-5.6 Sol
n25
CURRENT RECORD0.006626483934634
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n26
CURRENT RECORD0.006403292190753
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n27
CURRENT RECORD0.006173897499222
Medium
Record holderSigmoid with Codex
Solution methodAI · OpenAI: GPT-5.6 Sol
n28
CURRENT RECORD0.005944552050489
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n29
CURRENT RECORD0.005737979655504
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol
n30
CURRENT RECORD0.005541145985860
Medium
Record holder游侠
Solution methodAI · OpenAI: GPT-5.6 Sol

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/optimal-quantization.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/optimal-quantization.json
BibTeX (click to copy)
@misc{minmaxarena-optimal-quantization-2026-10,
  title  = {{Optimal quantization in the unit square} (P55)},
  author = {{MinMax Arena}},
  year   = {2026},
  note   = {Machine-verified records, 2026-10 edition},
  url    = {https://minmaxarena.com/data/editions/2026-10/optimal-quantization.json},
  license = {CC BY 4.0}
}
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