On Wed, 2008-10-08 at 15:18 +0200, Erik van der Werf wrote: > On Fri, Oct 3, 2008 at 2:33 PM, Don Dailey <[EMAIL PROTECTED]> wrote: > > I had heard somewhere that there are some who believe 8.0 is the right > > komi for 9x9 Chinese. I personally believed for a long time it was 7.0 > > based on statistical data of games. However that can be misleading. > > Do you understand why even numbers are very unlikely?
Yes, I understand that. I compiled from CGOS statistics all possible
results and their frequency. Here is a list of white results where the
actual games end with a score. You will notice that even scores are
much more common. There were just a few games that used 6.5 komi
because when I first started CGOS I had set 6.5 by mistake but I think
that was just for a few hours at most. The vast majority of these are
7.5 komi games:
39114 0.5
1488 1.5
20950 2.5
701 3.5
13948 4.5
534 5.5
10140 6.5
472 7.5
8202 8.5
385 9.5
7551 10.5
337 11.5
6489 12.5
309 13.5
5563 14.5
262 15.5
4895 16.5
260 17.5
4401 18.5
241 19.5
3750 20.5
187 21.5
3577 22.5
179 23.5
3418 24.5
180 25.5
3284 26.5
149 27.5
2881 28.5
122 29.5
2875 30.5
131 31.5
2503 32.5
134 33.5
2320 34.5
97 35.5
2237 36.5
67 37.5
2017 38.5
76 39.5
1908 40.5
69 41.5
1513 42.5
50 43.5
1478 44.5
50 45.5
1112 46.5
26 47.5
961 48.5
30 49.5
857 50.5
31 51.5
743 52.5
30 53.5
686 54.5
21 55.5
564 56.5
32 57.5
439 58.5
17 59.5
370 60.5
16 61.5
292 62.5
21 63.5
285 64.5
22 65.5
257 66.5
15 67.5
175 68.5
25 69.5
156 70.5
21 71.5
76 72.5
14 73.5
19 74.5
27 75.5
12 76.5
16 77.5
18 78.5
14 79.5
19 80.5
15 81.5
22 82.5
27 83.5
90 85.5
28407 88.5
>
> It's rather trivial, but somehow many people seem to miss it...
>
> On 9x9 the board we know that all intersections are either Black (B),
> White (W), or Neutral (N):
>
> B + W + N = 81
>
> Without seki:
>
> W = 81 - B (no neutral intersections in the final position, so N = 0)
>
> Score = B - (W + komi) = 2B - (81+komi)
>
> Consequently:
> with 5.5 komi Black needs 44 points to win,
> with 6.0 komi Black needs 44 points to win,
> with 6.5 komi Black needs 44 points to win,
> with 7.0 komi Black needs 44 points to tie,
> with 7.5 komi Black needs 45 points to win,
> with 8.0 komi Black needs 45 points to win,
> with 8.5 komi Black needs 45 points to win,
> with 9.0 komi Black needs 45 points to tie
>
> At high levels on 9x9 it appears to be extremely difficult for Black
> to get 45 points.
>
> With seki:
>
> N = even
>
> For the common type of seki, where the stones living in seki share two
> liberties, the perfect komi is again an odd number; results are
> therefore consistent with the numbers above (without seki).
>
> N = odd
>
> Only if optimal play inevitably leads to a seki with an odd number of
> neutral intersections the perfect komi becomes an even number (in
> which case 7.5 might make sense). However, given what is known from
> professional level 9x9 games this seems unlikely.
>
> If there really are persons that believe that the perfect komi on 9x9
> should be 8.0 then I would very much like to see a game record of such
> a game... I'm sure some top 9x9 programs will have fun trying to tear
> it apart :-)
>
> Erik
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