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Subject: Re: To NON-believers in EGTB benefits... (some engines benefit greatly..

Author: Tord Romstad

Date: 04:32:27 11/21/05

Go up one level in this thread


On November 21, 2005 at 03:17:15, A. Steen wrote:

>On November 21, 2005 at 03:05:16, Tord Romstad wrote:
>
>:: everything else agreed with ::
>
>>In my
>>opinion, a better way to use EGTBs would be to use them as an oracle
>>when implementing endgame evaluation rules.  We could analyse all
>>the positions in an EGTB and try to find general rules and patterns
>>which enable us to classify the majority of positions as won, drawn
>>or lost without consulting the EGTB.
>
>I have spent years doing this. :(
>
>Except for the simple cases, where algorithms already produce good results and
>make nearly optimal moves (without much shuffling), it is just too hard.

It is not easy, but far from impossible.

It has been done successfully for centuries, even without computers and
EGTBs.  Open any advanced endgame textbook.  You will find big classes
of endgames classified as won or drawn, sometimes by extremely complex
maneuvres which a chess program without EGTBs or special knowledge
wouldn't find even after hours of search.  For endgames which are too
hard to analyse exactly, you will often find very effective heuristic
rules for guessing whether a given position is won, and for finding the
winning plan.

Consider KRPKR as an example.  The complete EGTBs for this endgame
are about 150 MB of data, not counting the numerous transitions to
other endgames.  This is obviously far too much to memorise for
human players.  Nevertheless, even moderately strong human players
are able to play such endgames almost perfectly, because we have
been able to identify the most fundamental classes of won and drawn
positions, and to formulate some general high-level rules for how
to play.  That all this work was done before EGTBs were available,
and with very few inaccuracies, is truly amazing.  Doing similar
work today would be much easier.

When we have managed to replace the detailed, but unorganised
EGTB data with general rules, it is often easy to evaluate much
more complicated endgames correctly.  As a trivial example,
consider the following position:

[D]8/6k1/1r5p/8/8/5K2/R5PP/8 w -

For a human player who has studied basic endgame theory, it is
rather obvious that this is a draw.  It is clear that white
cannot create a passed pawn without allowing a Philidor-type
draw.  Arriving at the same conclusion armed with just the
raw EGTB data would probably require a very deep search.

>Maybe some neural network type of work might yield something.

It would be interesting, but I think this is better done by
humans assisted with a chess program and EGTBs than by an
unassisted computer.

John Nunn has done some fascinating work, but I still haven't
found the time to read it.

>As an extreme case, what pattern can we hope to find in the useful parts of
>KRRNKRR or KRBNKRB, in what appear to be just shufflings?

I doubt that we could find any interesting patterns here, but these
endgames have almost no practical importance.  How often do you see
KRBNKRB in real games?

Tord




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