Author: Christophe Theron
Date: 11:58:48 04/18/98
Go up one level in this thread
On April 17, 1998 at 17:21:35, Peter Fendrich wrote:
>On April 17, 1998 at 00:36:18, Christophe Theron wrote:
>
>- snip -
>>>
>>>The SEE code itself should be faster than Qsearch, shouldn't it?
>>
>>I don't think so.
>>
>>If your QSearch has only one, two or three positions to examine to get a
>>cutoff, I bet it is faster than your SEE.
>>
>>That's why I said this is counterintuitive. If you try to imagine what a
>>QSearch does, you can easily convince yourself that it is a very long
>>process. Think: it has to try every capture in the position, then every
>>capture in response, then... with no depth limit. If you assume there is
>>always 2, 3 or 4 captures available in any position, you come very
>>quickly to the conclusion that the QSearch has to be avoided by any
>>mean.
>>
>>That's what I thought in 1981 when I was writting my first chess
>>program. That's why I said that building a SEE was my very first idea
>>(at that time, I didn't know if anybody else had already tried this
>>idea).
>>
>>But QSearch is far more efficicient that it seems at first glance. For
>>example, take Crafty and let it think on a position. At the end of the
>>search, take a look at the number of total nodes visited, and the number
>>of nodes visited in QSearch.
>>
>>I tried this with an old Crafty version, and it seems that QSearch
>>visits only between 3 and 5 nodes for every node visited in the "full
>>width" search. Maybe it is even less, due to the way Bob counts the
>>nodes.
>>
>>For my program, Chess Tiger, the ratio is less than that.
>>
>>So depending on how your program is designed, a simple QSearch can be
>>faster than the best SEE you'll ever design, and far more reliable.
>>
>>It may or may not be the case. Try it out.
>>
>
>Of cource you have a point but it still doesn't hold for me probably due
>to different techniques which gives different views on this subject...
>I use a bitboard approach and generating captures is really nothing
>compared to going through a search.
>Futhermore the swapoff can be reduced, it isn't necessary to go throug
>all captures.
>But in the end, the SEE isn't as accurate as the QSearch and I still
>doesn't
>know which method is best for the deep iterations.
>One has to take into account that the QSearch misses more sofisticated
>tactics as well.
>
>When I make tests between different versions of my own program the
>QSearch
>version is slightly better but against other programs I don't see any
>real
>differences at all. That's why have a feeling that the SEE-version could
>gain more by extended evaluation or extensions. I haven't tried that
>yet.
>
>Peter
Ok, let us know what the result is...
Christophe
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