Re: Superko detection (was Re: [computer-go] M.Boon-Library)

[Don Dailey <drd@xxxxxxx>]

GHI seems to be much more serious in GO than in chess.  I am wondering
how it's normally handled in a GO program?   

I have thought of a couple of "solutions" which I don't believe are
good enough:

   1.  Never use values in the hash table that do not match the depth
       of the position you are attempting to score.

   2.  Do not store (or retrieve) positions where a ko is possible.

I don't know how much either of these help,  but I'm sure they don't
"solve" the problem and I doubt there is a complete solutions that 
doesn't cripple the benefits of the hash tables. 


- Don



   chrilly wrote:
   >>Does MadLab's search use transposition tables? If so, how does it deal
   >>with Graph-History Interaction?
   >>Erik

   > I have never really understand the point behind GHI. One can reach the same
   > position over 2 different variations/graphs. But what bad playing behaviour
   > is caused by GHI?
   > Stupid side-Question: What is SuperKo? Is it general repetition of position
   > and not just recapturing back one stone?
   > If it is really general repetition and if GHI has some effects on it, than
   > GHI would be also harmfull in chess. GHI seems to be a favorite topic of the
   > Maastricht research-group. Maybe Erik can explain it.

   If you store evaluation results for a position, then the result doesn't depend
   on just the position itself, but also on its history.

   For instance, position A is good for me because in some variation I can move to 
   the winning position B. So I store this information in a transposition table.

   However, if in another part of the search, I reach position A *after* having
   already reached B, then I cannot use the transposition table entry for A,
   since A is not so good for me now that I am not allowed (by superko) to move to 
   B again.


   regards,
   -John
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