Computer Chess Club Archives




Subject: Re: Very easy mate to solve.

Author: Heiner Marxen

Date: 21:06:25 12/31/01

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On December 31, 2001 at 22:45:25, leonid wrote:

>>The defending king has 5.25 flight squares on average (including the king's
>>square). That is a lot.  Delivering mate is not easy, then.
>>(This statistic is done _before_ the attackers move at ply 4)
>You do your statistic before specialized plys?

In this case Chest does part of the work at ply 4 and part of it at ply 3.

When doing a mate-in-two, and before searching any attacker move,
I do prepare this by collecting data, especially looking around what next
move the defender king could probably make, and how many escapes he would
have there.

Then, after execution of some attacker move, the prepared defender king move
(with largest escape chances) is tested for legality, and if legal,
Chest tries to prove, that whatever the attacker might do after this
defender king move (still not executed), cannot possibly be a mate move,
since it would not cover all escapes.

So the statistics is done in ply 4 (your numbering!), while the pruning
is done in ply 3.

>My idea is just to look for needed indication in ply 3. Ply 3, if counting goes
>from biggest ply down and end with number one. I do expect to generate all moves
>in ply 3 (black, defender side) and after see existence of checking moves
>(against white king) and number of legal moves for black king. All needed
>indication for searching certain moves more deeply exist already for free in ply
>3. Procedures must be wrote only to do the work when indication for success is
>apparent. I expect that working procedures could be easily written in  one week.
>Problem is to be ready for writing. For now my mind is not there.
>>Yes, if you do not yet do something like that, there is still a lot of
>>potential.  But it is not easy to do the necessary calculations quick enough.
>This part is somewhat surprised me and this is why I made my question before.
>It could be that you see for needed statistics before ply three and if it is
>favorable, you generate later only limited number of moves. Moves that just
>needed to obtain success. Then your logic save time needed for generation of all
>legal black moves in ply 3.

Every method that may save time conditionally, has to invest the time to
test whether or not it is possible just now.
If that test fails too often, or is itself too expensive,
the net effect is not positive.

>Cheers and Happy New Year!!!! We are already there.
>Feel big joy for all You Europeans that came finally to some kind of Union. New
>Union money, that start with coming 2002, is visible sign that this old dream is


But after being used for over 40 years to one kind of coins, I guess it will
take some time to get used to those funny looking now kind of coins.
Somehow they don't look like real money  ;-)



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