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Subject: Re: Tablebases an efficient solution?

Author: Rafael Andrist

Date: 07:57:45 02/12/06

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On February 11, 2006 at 14:50:01, h.g.muller wrote:

I have tried this out some years ago, but only for 2- and 3-men (other pieces
fixed). My short comments:

1. I recommend to use DTZ50 instead of DTM, because:
a) DTM can be missleading since it ignores the 50-move rule.
b) with DTZ50, one byte per EGTB-entry is sufficient.
c) if you do not have complete information and only an upper bound for DTM, you
can as well work with DTZ anyway.
d) IMO DTZ resp. DTZ50 seems to be the natural choice in blocked positions

2. For the engine, it is difficult to decide if it is worth to create ad hoc an
EGTB or to rely on the traditional search instead.

3. A generation of all necessary sub-EGTB is often not practical during a game.
a) This is of course not a problem if there are e.g. 7 men in total on the
board, no promotions are possible and all necessary 6-men EGTB are available.
b) If you are willing to introduce some uncertainty, you can apply rules to
judge the positions instead of recursively creating sub-EGTB.
c) This problem also affects 2) because it is difficult to guess which sub-EGTB
are really needed in practice (not for optimal play)

4. With todays hardware and optimized EGTB generation algorithms, calculating
5-men for the root position could be doable during a game. But often the time
will be very limited when it comes to such endgames. Somewhere else in the
search tree, i think only the calculation of 2- or 3-men is practicable.

regards
Rafael Andrist





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