Author: Christophe Theron
Date: 08:11:16 07/19/99
Go up one level in this thread
On July 19, 1999 at 05:05:23, Tania Devora wrote:
(snip)
>LAUREN PLEASE lOOK this last position
>
>
>White : Kc8. Ra2.
>pawns : b6.
>
>Black : Ra8. Bb8.
>pawns : a7. b7.
>
>Almost all the programs can see this mate. MATE in 3.
>BUT FRITZ 5.32 Can't DO IT !! A simple mate in 3.
>Fritz looks Rd7 ?? Absolutely a mistake.
Dear Tania,
This position has been shown here several times. It is simply a zugzwang
position. That means that after the key move (Ra6), black is in zugzwang (that
means that not moving, if it was allowed, would be the best thing for him).
Fritz, like many other "null move" programs, has sometimes problems with
zugzwang positions. It is because of the "null move" algorithm, which is on the
other side very powerful in 99.9% of the chess positions. For example if Fritz
was not using null move, you can expect that it would be maybe 50 times slower
than it is.
But when a zugzwang position occurs, Fritz can have problems to see that the
side in zugzwang is losing.
BTW, Hiarcs uses the same algorithm, and also fails in some zugzwang positions.
This has been posted on this group only 3 or 4 days ago.
Here is the position:
2k1q3/2p3n1/p1Np4/3P3p/P2P1p2/1Q5P/1KP5/8 w - -
The right move seems to be h4!
After this move, it looks to me that black is in zugzwang, and that's why many
good chess programs, including Hiarcs, will badly fail on this position.
So, every time you want to post a position where a program fails to find the
solution, first check if one side is in zugzwang after the key move. If it is
so, don't waste your time posting it. We perfectly know that many programs have
problems with these zugzwang positions, and if you ask I'm sure several people
could provide plenty of them.
>The programs are very different, you can't say that a program is bad why it
>doesnt see one move.
In this regard, Fritz and Hiarcs are very similar. They use null move and would
fail on some zugzwang positions, and both would look very stupid.
Christophe
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