P82 · Packing and covering · Classic · Hard

Equal circles in regular polygons · m = 5 · n = 28

Pack n equal circles into the true regular m-gon with centre (1,1), circumradius 1 and first vertex (2,1), maximising their radius.

Instancem = 5 · n = 28
ObjectiveMaximize circle radius

Formal definition

  • ContainerThe editor and certificate normalize to the true regular m-gon with centre (1,1), circumradius 1 and first vertex (2,1). 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.
  • ConstraintsExactly n congruent shapes lie wholly in the container with pairwise disjoint interiors. Polygon rotations are independent, not limited to quarter turns.
  • 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.
  • ObjectiveCircle radius r, larger is better; the container circumradius is 1.
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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 record-holding arrangement for Equal circles in regular polygons m = 5 · n = 28, 0.145444423
Current leader

0.145444423

circle radius

Answer sourceEckard Specht
Solution methodPublished reference construction
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Record holder's solver noteNo solver note yet (expand)

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ANSWER FORMAT

How to write your answer

the true regular m-gon with centre (1,1), circumradius 1 and first vertex (2,1)

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.

The current leader's answer

{
  "placements": [
    {
      "turn": "0",
      "x": "0.336427429",
      "y": "1.245434422"
    },
    {
      "turn": "0",
      "x": "0.336427429",
      "y": "0.785304383"
    },
    {
      "turn": "0",
      "x": "0.392108523",
      "y": "0.499794423"
    },
    {
      "turn": "0",
      "x": "0.442102169",
      "y": "1.516449497"
    },
    {
      "turn": "0",
      "x": "0.514434195",
      "y": "1.015369403"
    },
    {
      "turn": "0",
      "x": "0.624672963",
      "y": "1.284560293"
    },
    {
      "turn": "0",
      "x": "0.624672963",
      "y": "0.746178512"
    },
    {
      "turn": "0",
      "x": "0.668760257",
      "y": "0.409904826"
    },
    {
      "turn": "0",
      "x": "0.718753903",
      "y": "1.606339095"
    },
    {
      "turn": "0",
      "x": "0.804761146",
      "y": "0.997297786"
    },
    {
      "turn": "0",
      "x": "0.881059229",
      "y": "0.608765250"
    },
    {
      "turn": "0",
      "x": "0.899895750",
      "y": "1.378734277"
    },
    {
      "turn": "0",
      "x": "0.945411991",
      "y": "0.320015228"
    },
    {
      "turn": "0",
      "x": "0.995405637",
      "y": "1.696228692"
    },
    {
      "turn": "0",
      "x": "1.052039403",
      "y": "0.844099271"
    },
    {
      "turn": "0",
      "x": "1.060384886",
      "y": "1.136124387"
    },
    {
      "turn": "0",
      "x": "1.157710963",
      "y": "0.518875653"
    },
    {
      "turn": "0",
      "x": "1.176547484",
      "y": "1.468623875"
    },
    {
      "turn": "0",
      "x": "1.251591096",
      "y": "0.225608769"
    },
    {
      "turn": "0",
      "x": "1.283088114",
      "y": "1.739299725"
    },
    {
      "turn": "0",
      "x": "1.328691137",
      "y": "0.754209674"
    },
    {
      "turn": "0",
      "x": "1.337036620",
      "y": "1.226013984"
    },
    {
      "turn": "0",
      "x": "1.446728288",
      "y": "0.485931652"
    },
    {
      "turn": "0",
      "x": "1.466898380",
      "y": "1.486306598"
    },
    {
      "turn": "0",
      "x": "1.508016794",
      "y": "0.990679963"
    },
    {
      "turn": "0",
      "x": "1.617708463",
      "y": "0.721265673"
    },
    {
      "turn": "0",
      "x": "1.637878555",
      "y": "1.250972577"
    },
    {
      "turn": "0",
      "x": "1.814411182",
      "y": "0.999975974"
    }
  ],
  "radius": "0.145444423"
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer

Instance parameters

{
  "n": 28,
  "sides": 5
}

The current leader's answer

{
  "placements": [
    {
      "turn": "0",
      "x": "0.336427429",
      "y": "1.245434422"
    },
    {
      "turn": "0",
      "x": "0.336427429",
      "y": "0.785304383"
    },
    {
      "turn": "0",
      "x": "0.392108523",
      "y": "0.499794423"
    },
    {
      "turn": "0",
      "x": "0.442102169",
      "y": "1.516449497"
    },
    {
      "turn": "0",
      "x": "0.514434195",
      "y": "1.015369403"
    },
    {
      "turn": "0",
      "x": "0.624672963",
      "y": "1.284560293"
    },
    {
      "turn": "0",
      "x": "0.624672963",
      "y": "0.746178512"
    },
    {
      "turn": "0",
      "x": "0.668760257",
      "y": "0.409904826"
    },
    {
      "turn": "0",
      "x": "0.718753903",
      "y": "1.606339095"
    },
    {
      "turn": "0",
      "x": "0.804761146",
      "y": "0.997297786"
    },
    {
      "turn": "0",
      "x": "0.881059229",
      "y": "0.608765250"
    },
    {
      "turn": "0",
      "x": "0.899895750",
      "y": "1.378734277"
    },
    {
      "turn": "0",
      "x": "0.945411991",
      "y": "0.320015228"
    },
    {
      "turn": "0",
      "x": "0.995405637",
      "y": "1.696228692"
    },
    {
      "turn": "0",
      "x": "1.052039403",
      "y": "0.844099271"
    },
    {
      "turn": "0",
      "x": "1.060384886",
      "y": "1.136124387"
    },
    {
      "turn": "0",
      "x": "1.157710963",
      "y": "0.518875653"
    },
    {
      "turn": "0",
      "x": "1.176547484",
      "y": "1.468623875"
    },
    {
      "turn": "0",
      "x": "1.251591096",
      "y": "0.225608769"
    },
    {
      "turn": "0",
      "x": "1.283088114",
      "y": "1.739299725"
    },
    {
      "turn": "0",
      "x": "1.328691137",
      "y": "0.754209674"
    },
    {
      "turn": "0",
      "x": "1.337036620",
      "y": "1.226013984"
    },
    {
      "turn": "0",
      "x": "1.446728288",
      "y": "0.485931652"
    },
    {
      "turn": "0",
      "x": "1.466898380",
      "y": "1.486306598"
    },
    {
      "turn": "0",
      "x": "1.508016794",
      "y": "0.990679963"
    },
    {
      "turn": "0",
      "x": "1.617708463",
      "y": "0.721265673"
    },
    {
      "turn": "0",
      "x": "1.637878555",
      "y": "1.250972577"
    },
    {
      "turn": "0",
      "x": "1.814411182",
      "y": "0.999975974"
    }
  ],
  "radius": "0.145444423"
}

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

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