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Subject: Re: Very easy mate to solve.

Author: leonid

Date: 04:44:24 12/31/01

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Hi, Heiner!


>>What is "immediate mate move"?
>
>If the defender is to move, and the current depth is at least 3 (mate-in-2
>or more left after defender move), and the defender has more than just his bare
>king, then, before even generating the legal defender moves, Chest calls
>the special mate-move-generator, trying to find a "mate the attacker in 1".
>The moves found by that move generator are just candidates, and must be
>executed to verify them, but there are not many false candidates.

This is probably what I expected to write but never come to my code. Recently I
put all kind of counters in plys three. What is interesting to see there is that
biggest part of all positions for this ply have checking moves. So, if this side
use its checking move and have certain number of legal moves for his king, it
have good chances to escape mate after response. All work should be in finding
how many initially legal king's moves are needed. Also it is important to see if
each if its moves do not diminish number of already existing king's escape
moves.


>>>That really sounds like a (special sort of) killer heuristic.
>>
>>Will try to remember this strange expression.
>
>To me it appears to be standard term in the computer chess community.

After having everything named in my own way in intensive initial writing, it is
too hard for me to retain some words that are not explicit. Heuristic is not
something that we use in daily English.

>>And how Holger wrote its move sorting? Did he started by doing move generator
>>first? Don't be afraid to be very descriptive. It is just too interesting to
>>know how other big projects started.
>
>First, we developped together some complete version of Chest, including
>move generator, hash table etc.
>Sorting of defender moves was done by the simple "basic" logic I already
>explained, and which still is used for depth=2 analysis.
>
>Then we (Holger and I) had some intensive discussions, how to improve the
>situation.  The defenders most important job has to be to cut down the
>tree size.  On that we did agree.  But how to achieve this in a better way?
>The simple heuristic we already had appeared to be not appropriate for
>really deep analysis, say depth=6 remaining.  Tree sizes would vary very
>drastically depending on the choice of the defender move.  And to avoid
>such large trees we felt that some more effort should be spent.
>
>We agreed on a benchmark position: "Das unsterbliche Schachproblem"
>by C.Bayer, a mate-in-9:
>[D]3Q4/5q1k/4ppp1/2Kp1N1B/RR6/3P1r2/4nP1b/3b4 w - -
>
>Holger was interested to do research and experiments on this, and tried
>to work on the tree size estimation idea.  He spent 2 weeks of his vacations
>on this, and came back with an extended version of Chest, which now solved
>that mate-in-9 much, much faster.  Actually, it was the first time that
>we did solve that position (took 32.5 hours on a HP9000-835 in 1991).

If this man was able to do everything in two weeks, he was stronger that me.
I was coming all two weeks with some kind of new ideas and biggest part of them
never worked.

>So I took his code, cleaned it up somewhat, added some comments, and
>asked him about all those peculiar details in there, which I did not
>understand.  Most often he could not explain much more than "I tried
>several things, and this worked best... don't know why".

So, he, probably, did like me after statistics.

Thanks, Heiner, for saying how it was done!

Leonid.



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