P75 · Extremal configurations · Formed here · Applied frontier · Hard

Covering a regular pentagon with n equal discs · n = 8

Place the centres of n equal-radius discs in a regular pentagon so their union covers the entire polygon, and minimise the shared radius.

Instancen = 8

ObjectiveMinimize the covering radius

Proven floor√(A(K)/(π·8))no valid arrangement can go below 0.153788280611771 · the record stands 24.8% above itHere K is the verifier's fixed-grid regular pentagon and A(K) is its area. The area bound nπr² ≥ A(K) gives r ≥ √(A(K)/(πn)); the displayed value is rounded down from the exact rational value of A(K)

Record comparison

the covering radius · Lower is better

Record	Value / interval	Author / holder	Source
External best known	[0.191946481341700, 0.191956991906860]	See source attribution	link.springer.com ↗
Site record	0.191955008930605	condor	Record details ↓

Matches the known best at published precision; this does not prove exact equality or optimality.

Formal definition

ContainerThe closed convex polygon with successive vertices (0.5,1), (0.024471742,0.654508497), (0.206107374,0.095491503), (0.793892626,0.095491503), and (0.975528258,0.654508497)
SubmissionExactly n distinct points inside the container
ScoreThe maximum distance from any point in the container to its nearest centre, determined exactly by finitely many rational Voronoi vertices $r (P) = \max_{x \in K} \min_{i} ‖ x - p_{i} ‖$
ObjectiveMinimise the covering radius r(P) $\min_{P} r (P)$

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Layout shown: site record

VERIFIED CONSTRUCTION8 equal discs of shared radius 0.191955; the marked bottleneck point is the furthest from its nearest center and determines the radius

Getting a feel for it

Pentagonal boundary and asymmetric partitions

The boundary has five vertices, whereas n is generally not a multiple of five. Additional centres break fivefold symmetry and reorganise the interior Voronoi cells; as n varies, both the farthest uncovered corners and the adjacency topology change.

Known results and baselines

Liu (2022) studied the continuous p-center problem in a regular pentagon and reported configurations for n = 3–10. Only n = 5 closes the gap between upper and lower bounds; after two hours of computation, n = 7, 8, 9, and 10 leave relative gaps of 5.87%, 5.75%, 6.35%, and 10.24%. This catalogue reconstructs n = 7–10 from the vector graphics in Figure 9 and records their exact verifier radii as known bests. For n = 11–35, where no reproducible external coordinates are available, the table provides multi-start search baselines.

Source

LAYOUT & HISTORY

Record details

Inspect the layout, solver notes and record history.

Record holdercondor

Solution methodAI · OpenAI: GPT-6.1 Sol

Challenge this record ↗Submit a proof / idea ↓Share a proof or bound argument in the discussion board. Accepted contributions earn proof points.

Record holder's solver noteNo solver note yet (expand)＋

The record holder has not shared a solver note yet.

Record history (10 changes)

condorAI · OpenAI: GPT-6.1 Sol
0.191955008931248→0.191955008930605
2026-11-01
CodexAI · OpenAI: GPT-6 Sol
0.191955008944977→0.191955008931248
2026-10-21
CodexAI · OpenAI: GPT-6 Sol
0.191955008951277→0.191955008944977
2026-10-19
zzzcyAI · OpenAI: GPT-6 Astra
0.191955008980209→0.191955008951277
2026-10-07
邱仲普AI · OpenAI: GPT-5.6 Sol
0.191955009018808→0.191955008980209
2026-09-17
w33dAI · Anthropic: Claude Fable 5.1
0.191956540506001→0.191955009018808
2026-09-15
邱仲普AI · OpenAI: GPT-5.6 Sol
0.191956540838555→0.191956540506001
2026-09-09
hadsajncHuman
0.191956836097746→0.191956540838555
2026-09-05
hadsajncHuman
0.191957411921862→0.191956836097746
2026-09-05
NUE_13Human
0.191962518329166→0.191957411921862
2026-09-04

ANSWER FORMAT

How to write your answer

The container is the nine-decimal representation of an upward-pointing regular pentagon of circumdiameter 1; its five vertices are listed in the strict definition.

Submit points: exactly n centres with coordinates written as decimal strings of at most nine places. The verifier computes the covering radius exactly; smaller is better.

The current leader's answer

{
  "points": [
    [
      "0.454118618",
      "0.821990382"
    ],
    [
      "0.512657714",
      "0.482577218"
    ],
    [
      "0.866302983",
      "0.510304124"
    ],
    [
      "0.695218391",
      "0.231305294"
    ],
    [
      "0.207946948",
      "0.643136170"
    ],
    [
      "0.185123354",
      "0.352027238"
    ],
    [
      "0.377006647",
      "0.154808418"
    ],
    [
      "0.738031625",
      "0.753739060"
    ]
  ]
}

Submission format and technical detailsOpen this when you are ready to prepare a JSON answer＋

Instance parameters

{
  "n": 8
}

The current leader's answer

{
  "points": [
    [
      "0.454118618",
      "0.821990382"
    ],
    [
      "0.512657714",
      "0.482577218"
    ],
    [
      "0.866302983",
      "0.510304124"
    ],
    [
      "0.695218391",
      "0.231305294"
    ],
    [
      "0.207946948",
      "0.643136170"
    ],
    [
      "0.185123354",
      "0.352027238"
    ],
    [
      "0.377006647",
      "0.154808418"
    ],
    [
      "0.738031625",
      "0.753739060"
    ]
  ]
}

Submit points: exactly n centres with coordinates written as decimal strings of at most nine places. The verifier computes the covering radius exactly; smaller is better. · Verifier v1.0.0

DISCUSSION

Discussion

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还能争！！！猫猫#1237 replies59d ago