Computer Chess Club Archives




Subject: Re: Very easy mate to solve. Correction!!!

Author: Heiner Marxen

Date: 07:13:44 12/31/01

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On December 31, 2001 at 07:11:56, leonid wrote:

>Hi, Heiner!

Hello Leonid!

>By thinking about your remark about defender side, I found that I did one
>mistake. To be sure that this time I not lost next "small" nuance, I went
>actually back to my mate solver code to read it before speaking. There I found
>what I wanted to find and even why I was confused about "active" and "passive"
>moves. But before every thing else, exact mate solver move construction.
>Each move, composed from attacking and defending ply, contain identical sorting
>for both sides. The same move generator and two move sorting for two plys. Both
>sides try as hard as they can reach mate.
>In attacking side it is only move that lead to mate that is solved as the next
>"best move".

I.e. you save a move that does solve this current position.

>On defending side it is move that lead to mate, or last move of search that is
>saved as "best move".
>Previous mistake from my side was in saying that it is only move that lead to
>mate that is saved for defending side.

Again, you save that move, that "solves" this current position for the defender.
A defender "solves" a position if he avoids its own forced mate.

>One mistake, even before my last, I found when reading description of defending
>side. There "best move" is saved in variable that is "best passive". In reality,
>here this move have nothing to do with "best passive move", even if it use this
>variable. This variable have sense in other part of chess program.
>Sorry for mistake!

Never mind!  Thanks for clearing up!

Some (minor) questions remain:
- meaning of "active" and "passive" move:  I suspect an "active" move is one
  that checks the opposing king.  Correct?
- Storing saved "best moves" for each ply:  do you index from top (i.e. with
  the depth you have searched into the tree, already), or do you index from
  bottom (i.e. by the remaining depth to go/search)?

Intuitively I would index by remaining depth, but the other way may make sense,



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