P87 · Packing and covering · Classic · Easy

Equal discs covering a disc · n = 38

Cover the largest possible disc with n unit-radius discs. Maximise the covered disc radius.

Instancen = 38
ObjectiveMaximize covered disc radius

Record comparison

covered disc radius · Higher is better
RecordValue / intervalAuthor / holderSource
External best known——No reference listed
Site recordNo player record yet——

Formal definition

  • ContainerThe editor and certificate normalize to the closed unit disc centred at (1,1). This is a coordinate convention only; scores use the literature's unit-piece scale. Boundary contact is allowed.
  • SubmissionSubmit {radius, placements:[{x,y,turn},…]}, with decimal strings of at most nine places. x,y are centres; circles require turn=0, polygons use turn=tan(θ/2). Coordinates and turn lie in ±4; 0 < radius ≤ 4.
  • ConstraintsThe n distinct centres lie in the target disc. Covering discs may overlap and protrude, but must cover every target point.
  • PrecisionInput decimals are exact rationals; regular-polygon vertices are algebraic, not rounded templates. Feasibility has no floating-point tolerance. A finite-decimal certificate is not a continuous optimality proof.
  • ObjectiveCovered disc radius R = 1/r, larger is better.
Open the full editor ↗

Layout shown: starter layout

VERIFIED CONSTRUCTIONVERIFIED CONSTRUCTION

Getting a feel for it

Source and certificate

External targets are converted with their printed precision; decimal coordinate certificates are separate. Reconstruction loss never lowers the literature target, and a source construction is not automatically an optimality proof.

Source
The current arrangement for Equal discs covering a disc n = 38
LAYOUT & HISTORY

Starter layout

Inspect the layout, solver notes and record history.

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ANSWER FORMAT

How to write your answer

the closed unit disc centred at (1,1)

Submit {radius, placements:[{x,y,turn},…]}, with decimal strings of at most nine places. x,y are centres; circles require turn=0, polygons use turn=tan(θ/2). Coordinates and turn lie in ±4; 0 < radius ≤ 4.

Starter answer

{
  "placements": [
    {
      "turn": "0",
      "x": "0.988219188",
      "y": "0.982012149"
    },
    {
      "turn": "0",
      "x": "1.006592851",
      "y": "1.309691426"
    },
    {
      "turn": "0",
      "x": "1.287277726",
      "y": "1.118188804"
    },
    {
      "turn": "0",
      "x": "0.710645661",
      "y": "1.174043646"
    },
    {
      "turn": "0",
      "x": "1.267815309",
      "y": "0.793873856"
    },
    {
      "turn": "0",
      "x": "0.690069411",
      "y": "0.843972709"
    },
    {
      "turn": "0",
      "x": "0.966883737",
      "y": "0.654524117"
    },
    {
      "turn": "0",
      "x": "1.297870814",
      "y": "1.436577958"
    },
    {
      "turn": "0",
      "x": "0.729179696",
      "y": "1.505164809"
    },
    {
      "turn": "0",
      "x": "1.570402450",
      "y": "0.930998269"
    },
    {
      "turn": "0",
      "x": "1.015240287",
      "y": "1.639045038"
    },
    {
      "turn": "0",
      "x": "0.413357086",
      "y": "1.036221700"
    },
    {
      "turn": "0",
      "x": "1.589475031",
      "y": "1.246982997"
    },
    {
      "turn": "0",
      "x": "1.245579878",
      "y": "0.466494252"
    },
    {
      "turn": "0",
      "x": "0.437975205",
      "y": "1.369178559"
    },
    {
      "turn": "0",
      "x": "0.667472786",
      "y": "0.514001671"
    },
    {
      "turn": "0",
      "x": "1.547366562",
      "y": "0.610222107"
    },
    {
      "turn": "0",
      "x": "0.392673047",
      "y": "0.705180586"
    },
    {
      "turn": "0",
      "x": "0.944121201",
      "y": "0.326872985"
    },
    {
      "turn": "0",
      "x": "1.270599466",
      "y": "1.783724884"
    },
    {
      "turn": "0",
      "x": "1.633307122",
      "y": "1.534868699"
    },
    {
      "turn": "0",
      "x": "0.734090939",
      "y": "1.839224990"
    },
    {
      "turn": "0",
      "x": "0.479420466",
      "y": "1.714481128"
    },
    {
      "turn": "0",
      "x": "1.878147857",
      "y": "1.055388468"
    },
    {
      "turn": "0",
      "x": "1.854931206",
      "y": "0.772601613"
    },
    {
      "turn": "0",
      "x": "0.139638871",
      "y": "1.201339249"
    },
    {
      "turn": "0",
      "x": "1.042977146",
      "y": "1.957448540"
    },
    {
      "turn": "0",
      "x": "0.118658193",
      "y": "0.914807333"
    },
    {
      "turn": "0",
      "x": "1.498290997",
      "y": "0.271456375"
    },
    {
      "turn": "0",
      "x": "1.876557069",
      "y": "1.385385902"
    },
    {
      "turn": "0",
      "x": "1.240264209",
      "y": "0.148990514"
    },
    {
      "turn": "0",
      "x": "0.390026153",
      "y": "0.361313155"
    },
    {
      "turn": "0",
      "x": "0.625571569",
      "y": "0.198608850"
    },
    {
      "turn": "0",
      "x": "0.186708092",
      "y": "1.539089943"
    },
    {
      "turn": "0",
      "x": "1.795828588",
      "y": "0.436447976"
    },
    {
      "turn": "0",
      "x": "0.119619741",
      "y": "0.571253304"
    },
    {
      "turn": "0",
      "x": "1.508901279",
      "y": "1.742028611"
    },
    {
      "turn": "0",
      "x": "0.920875425",
      "y": "0.023652422"
    }
  ],
  "radius": "0.191901867"
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer+

Instance parameters

{
  "n": 38,
  "sides": 5
}

Starter answer

{
  "placements": [
    {
      "turn": "0",
      "x": "0.988219188",
      "y": "0.982012149"
    },
    {
      "turn": "0",
      "x": "1.006592851",
      "y": "1.309691426"
    },
    {
      "turn": "0",
      "x": "1.287277726",
      "y": "1.118188804"
    },
    {
      "turn": "0",
      "x": "0.710645661",
      "y": "1.174043646"
    },
    {
      "turn": "0",
      "x": "1.267815309",
      "y": "0.793873856"
    },
    {
      "turn": "0",
      "x": "0.690069411",
      "y": "0.843972709"
    },
    {
      "turn": "0",
      "x": "0.966883737",
      "y": "0.654524117"
    },
    {
      "turn": "0",
      "x": "1.297870814",
      "y": "1.436577958"
    },
    {
      "turn": "0",
      "x": "0.729179696",
      "y": "1.505164809"
    },
    {
      "turn": "0",
      "x": "1.570402450",
      "y": "0.930998269"
    },
    {
      "turn": "0",
      "x": "1.015240287",
      "y": "1.639045038"
    },
    {
      "turn": "0",
      "x": "0.413357086",
      "y": "1.036221700"
    },
    {
      "turn": "0",
      "x": "1.589475031",
      "y": "1.246982997"
    },
    {
      "turn": "0",
      "x": "1.245579878",
      "y": "0.466494252"
    },
    {
      "turn": "0",
      "x": "0.437975205",
      "y": "1.369178559"
    },
    {
      "turn": "0",
      "x": "0.667472786",
      "y": "0.514001671"
    },
    {
      "turn": "0",
      "x": "1.547366562",
      "y": "0.610222107"
    },
    {
      "turn": "0",
      "x": "0.392673047",
      "y": "0.705180586"
    },
    {
      "turn": "0",
      "x": "0.944121201",
      "y": "0.326872985"
    },
    {
      "turn": "0",
      "x": "1.270599466",
      "y": "1.783724884"
    },
    {
      "turn": "0",
      "x": "1.633307122",
      "y": "1.534868699"
    },
    {
      "turn": "0",
      "x": "0.734090939",
      "y": "1.839224990"
    },
    {
      "turn": "0",
      "x": "0.479420466",
      "y": "1.714481128"
    },
    {
      "turn": "0",
      "x": "1.878147857",
      "y": "1.055388468"
    },
    {
      "turn": "0",
      "x": "1.854931206",
      "y": "0.772601613"
    },
    {
      "turn": "0",
      "x": "0.139638871",
      "y": "1.201339249"
    },
    {
      "turn": "0",
      "x": "1.042977146",
      "y": "1.957448540"
    },
    {
      "turn": "0",
      "x": "0.118658193",
      "y": "0.914807333"
    },
    {
      "turn": "0",
      "x": "1.498290997",
      "y": "0.271456375"
    },
    {
      "turn": "0",
      "x": "1.876557069",
      "y": "1.385385902"
    },
    {
      "turn": "0",
      "x": "1.240264209",
      "y": "0.148990514"
    },
    {
      "turn": "0",
      "x": "0.390026153",
      "y": "0.361313155"
    },
    {
      "turn": "0",
      "x": "0.625571569",
      "y": "0.198608850"
    },
    {
      "turn": "0",
      "x": "0.186708092",
      "y": "1.539089943"
    },
    {
      "turn": "0",
      "x": "1.795828588",
      "y": "0.436447976"
    },
    {
      "turn": "0",
      "x": "0.119619741",
      "y": "0.571253304"
    },
    {
      "turn": "0",
      "x": "1.508901279",
      "y": "1.742028611"
    },
    {
      "turn": "0",
      "x": "0.920875425",
      "y": "0.023652422"
    }
  ],
  "radius": "0.191901867"
}

Submit {radius, placements:[{x,y,turn},…]}, with decimal strings of at most nine places. x,y are centres; circles require turn=0, polygons use turn=tan(θ/2). Coordinates and turn lie in ±4; 0 < radius ≤ 4. · Verifier v1.0.0

DISCUSSION

Discussion

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