P56 · Extremal configurations · Formed here · Applied frontier · Weak baseline · Easy

The most uniform sampling mesh in the unit square · n = 25

Place n points in the unit square. Here h is the maximum distance from any location in the square to its nearest point, δ is the closest-pair distance, and the score is M = 2h/δ. Make M as small as possible.

Instancen = 25
ObjectiveMinimize the uniformity M

Record comparison

the uniformity M · Lower is better
RecordValue / intervalAuthor / holderSource
External best known——No reference listed
Site recordNo player record yet——

Formal definition

  • ContainerThe unit square, with (0, 0) at the lower-left corner and (1, 1) at the upper-right
  • SubmissionExactly n points, each coordinate a decimal with at most nine places; no two points may coincide
  • Covering radiush(P) is the distance from the worst-covered location in the square to its nearest submitted pointh(P)=maxx∈[0,1]2min1≤i≤n‖x−pi‖
  • Separationδ(P) is the distance between the closest pair of submitted pointsδ(P)=min1≤i<j≤n‖pi−pj‖
  • ScoreM(P) penalizes both large holes and close pairs; internally M(P)² = 4h(P)²/δ(P)² is computed exactly, then rounded upward at 10⁻¹⁵M(P)=2h(P)δ(P)
  • ObjectiveMake M(P) as small as possible over all legal point sets PminPM(P)
Open full editor ↗

Layout shown: starter layout

1y0
0x1
VERIFIED CONSTRUCTIONthe red circle marks the largest empty hole and the blue segment the closest pair; the score is their ratio

Getting a feel for it

An analogy: siting base stations

Think of the n points as n base stations. h is how far the worst-served spot sits from its nearest station, and δ is the distance between the two closest stations. M = 2h/δ penalizes both large uncovered holes and crowded pairs.

Where the room for improvement is

A square grid gives M = √2 ≈ 1.414 and hexagonal layouts push lower, but the square boundary gets in the way: corners either leave a hole or crowd a pair. Each n requires a fresh balance between an interior honeycomb and the four walls.

Where the frontier is

Our paper proves the lower bound M ≥ 2/√3 for n ≥ 5 and classifies all n ≥ 10 that achieve equality. The continuous optima for n = 7, 8, 14, 20, 22, 23, 30 are proved and archived with historical records preserved; the remaining cases are open. Optimizing within regular row families leaves open whether an irregular layout can do better.

Source
The current arrangement for The most uniform sampling mesh in the unit square n = 25
LAYOUT & HISTORY

Starter layout

Inspect the layout, solver notes and record history.

Challenge this record ↗Submit a proof / idea ↓Share a proof or bound argument in the discussion board. Accepted contributions earn proof points.
Record history (6 changes)
  1. MinMax ArenaHuman
    1.205581418742→1.205107111615
  2. 今天Human
    1.214962692264→1.205581418742
  3. 今天Human
    1.223544978934→1.214962692264
  4. TmrgHuman
    1.390474313184→1.223544978934
  5. 邱仲普AI · MoonshotAI: Kimi K3
    1.414213562374→1.390474313184
  6. 1.205107111615→1.414213562374
ANSWER FORMAT

How to write your answer

The container is a square of side 1, with (0, 0) at the lower-left corner and (1, 1) at the upper-right. Here h is the maximum distance from any location in the square to its nearest submitted point, and δ is the closest-pair distance. Coordinates are decimals such as "0.25", with at most nine decimal places.

Submit points, each coordinate written as a decimal string such as "0.25", to at most nine decimal places. The score is M = 2h/δ; smaller is better.

Starter answer

{
  "points": [
    [
      "0.000000000",
      "0.076821818"
    ],
    [
      "0.228459579",
      "0.076821818"
    ],
    [
      "0.456919158",
      "0.076821818"
    ],
    [
      "0.685378737",
      "0.076821818"
    ],
    [
      "0.913838316",
      "0.076821818"
    ],
    [
      "0.086161684",
      "0.288410909"
    ],
    [
      "0.314621263",
      "0.288410909"
    ],
    [
      "0.543080842",
      "0.288410909"
    ],
    [
      "0.771540421",
      "0.288410909"
    ],
    [
      "1.000000000",
      "0.288410909"
    ],
    [
      "0.000000000",
      "0.500000000"
    ],
    [
      "0.228459579",
      "0.500000000"
    ],
    [
      "0.456919158",
      "0.500000000"
    ],
    [
      "0.685378737",
      "0.500000000"
    ],
    [
      "0.913838316",
      "0.500000000"
    ],
    [
      "0.086161684",
      "0.711589091"
    ],
    [
      "0.314621263",
      "0.711589091"
    ],
    [
      "0.543080842",
      "0.711589091"
    ],
    [
      "0.771540421",
      "0.711589091"
    ],
    [
      "1.000000000",
      "0.711589091"
    ],
    [
      "0.000000000",
      "0.923178182"
    ],
    [
      "0.228459579",
      "0.923178182"
    ],
    [
      "0.456919158",
      "0.923178182"
    ],
    [
      "0.685378737",
      "0.923178182"
    ],
    [
      "0.913838316",
      "0.923178182"
    ]
  ]
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer+

Instance parameters

{
  "n": 25
}

Starter answer

{
  "points": [
    [
      "0.000000000",
      "0.076821818"
    ],
    [
      "0.228459579",
      "0.076821818"
    ],
    [
      "0.456919158",
      "0.076821818"
    ],
    [
      "0.685378737",
      "0.076821818"
    ],
    [
      "0.913838316",
      "0.076821818"
    ],
    [
      "0.086161684",
      "0.288410909"
    ],
    [
      "0.314621263",
      "0.288410909"
    ],
    [
      "0.543080842",
      "0.288410909"
    ],
    [
      "0.771540421",
      "0.288410909"
    ],
    [
      "1.000000000",
      "0.288410909"
    ],
    [
      "0.000000000",
      "0.500000000"
    ],
    [
      "0.228459579",
      "0.500000000"
    ],
    [
      "0.456919158",
      "0.500000000"
    ],
    [
      "0.685378737",
      "0.500000000"
    ],
    [
      "0.913838316",
      "0.500000000"
    ],
    [
      "0.086161684",
      "0.711589091"
    ],
    [
      "0.314621263",
      "0.711589091"
    ],
    [
      "0.543080842",
      "0.711589091"
    ],
    [
      "0.771540421",
      "0.711589091"
    ],
    [
      "1.000000000",
      "0.711589091"
    ],
    [
      "0.000000000",
      "0.923178182"
    ],
    [
      "0.228459579",
      "0.923178182"
    ],
    [
      "0.456919158",
      "0.923178182"
    ],
    [
      "0.685378737",
      "0.923178182"
    ],
    [
      "0.913838316",
      "0.923178182"
    ]
  ]
}

Submit points, each coordinate written as a decimal string such as "0.25", to at most nine decimal places. The score is M = 2h/δ; smaller is better. · Verifier v1.0.0

DISCUSSION

Discussion

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