Author: Christophe Theron
Date: 10:01:08 04/21/98
Go up one level in this thread
On April 20, 1998 at 17:39:39, Tord Romstad wrote:
>On April 20, 1998 at 16:19:10, Sylvain Renard wrote:
>
>>On April 20, 1998 at 15:33:57, Christophe Theron wrote:
>>
>>>Genius depth 6 means, I think, that the program is considering the first
>>>6 plies in a brute force manner (or nearly) and is considering
>>>selectively 4 plies more, followed by a QSearch.
>> Hello Christophe,
>>what makes you think it is 4 plies? I have always thought that
>>after the 6 plies of brute force, Genius searched 12 plies more
>>in a selective way and there was nothing else (these 12 plies
>>include the quiescence search). Have you an example where Genius
>>"sees" more than brute force + 12 (hash tables off , of course) ?
>> Sylvain
>
>Try this position (white to move):
>
> +---+---+---+---+---+---+---+---+
> 8 | | *K| *B| *R| | | | *R|
> +---+---+---+---+---+---+---+---+
> 7 | *P| *P| | | | | | |
> +---+---+---+---+---+---+---+---+
> 6 | | | | | | | | |
> +---+---+---+---+---+---+---+---+
> 5 | P | | *N| | | *P| *P| *Q|
> +---+---+---+---+---+---+---+---+
> 4 | | | N | | | | *N| |
> +---+---+---+---+---+---+---+---+
> 3 | R | | | | Q | | P | |
> +---+---+---+---+---+---+---+---+
> 2 | | | | B | | P | | |
> +---+---+---+---+---+---+---+---+
> 1 | | | R | | | B | K | |
> +---+---+---+---+---+---+---+---+
> a b c d e f g h
>
>Genius 3.0 and older does not find the mate (1.Qf4+ is mate in 21 plies)
>before search depth 9/21. However, Genius 4 and 5 finds the mate at much
>lower search depths. Because of this (and other positions) I believe
>that
>your conclusion is correct for old versions of Genius, but that the most
>recent versions extend some lines beyond the 12 plies of selective
>search.
>
>Tord
I did not try your position yet. Anyway I'll do it.
But before that, I want to mention something I noticed with Genius: it
is able to evaluate sometimes that a position is a mate in 1 without
having to do the mate move. It is the case in very obvious mate
situations were you can just mate by putting your queen near a trapped
king. If you find this situation, you know it is a mate in 1, and you
don't need to verify that by moving your queen and then try to move the
king out of check.
I don't know if this mate detection algorithm has been improved in
recent versions, but it could be the explanation: Genius does not need
to see the 21th ply to find the mate, because it knows it is mate in 1
just by looking at the position at the 19th or 20th ply.
Christophe
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