Table of Eyeshapes

Path: EyesCollection   · Prev: EyeShape   · Next: EyeLiberties
PageType: Path     Keywords: Life & Death

The following table summarizes the status of various eye shapes.

Legend

  • # to kill is the number of times that opponent must play within the eyeshape in order to effectively reduce it to a single eye, hence kill the (singel eyed) group (assuming alternating play after that point). Similarly # for seki". A '-' for "# to kill" indicates that the group can only be killed by capturing it outright. Of course, these values are merely of academic interest in some cases.
  • Status is the status of a group which is surrounded, and has a single eyespace of the indicated size and shape (assuming alternating play with opponent first), with no opponent's stones within the eyespace. "Unsettled" means that the status depends on who plays first (depends on sente); this is the case when "# to kill" is exactly 1.
  • # libs is the effective number of liberties (in the second sense) that the eyespace yields in a capturing race; see BigEyeLiberties. This assumes that life cannot be made immediately (or else the value is '-'), and does not count the stones inside which are used to prevent life from being made. Note that seki is as good as life for a capturing race.

Table

   Size       Shape    Status # to kill # for seki # libs
      1           -      dead         0          -      1
      2           -      dead         0          -      2
      3 ThreeInARow unsettled         1          -      3
          BentThree unsettled         1          -      3
      4 SquaredFour      dead         0          -      5
           BentFour     alive         2          -      5
        PyramidFour unsettled         1          -      5
              other     alive         2          -      5
      5 CrossedFive unsettled         1          -      8
          BulkyFive unsettled         1        (3)      8
               ****
                 *      alive         2        (3)      8
                ***
                 *      alive         2        (3)      8
                 *
                *
                ***     alive         2        (3)      8
                 *
              other     alive         -          3      8
      6 RabbittySix unsettled         1          -     12
              other     alive    varies        2–4     12
      7                 alive    varies        1–5     17
      8                 alive         -        2–6      -
    n>8                 alive         -     varies      -
                              (no more than n-2)

See also

Discussion

RobertJasiek: What is the purpose of this table? To summarise all cases of eye-like regions of the board regardless which intersections are occupied? To summarise all cases of empty eye-like regions? To summarise all cases of strong eye regions regardless which intersections are occupied? (There are few hundred of them.) To summarise all cases of empty strong eye regions? Some other purpose?


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This is a copy of the living page "Table of Eyeshapes" at Sensei's Library.
(OC) 2012 the Authors, published under the OpenContent License V1.0.
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