Computer Chess Club Archives




Subject: Re: Secrets of Rybka and Fruit from my point of view

Author: Vasik Rajlich

Date: 04:20:20 12/17/05

Go up one level in this thread

On December 16, 2005 at 15:49:39, Uri Blass wrote:

>On December 16, 2005 at 15:35:55, Vasik Rajlich wrote:
>>On December 16, 2005 at 13:34:43, Uri Blass wrote:
>>>On December 16, 2005 at 03:32:16, Vasik Rajlich wrote:
>>>>On December 16, 2005 at 00:56:04, Zappa wrote:
>>>>>On December 15, 2005 at 17:05:00, Sergei S. Markoff wrote:
>>>>>>1) Fruit.
>>>>>>Fruit search seems to be primitive. "History pruning" is a variation of
>>>>>>well-known idea. After implementing such method in SmarThink some years ago I
>>>>>>named it "history-based pruning" and then changed to "ordering-based pruning".
>>>>>>The outcome of such methods very depends of whole search model, but anyway
>>>>>>history pruning is not the key to Fruit strength.
>>>>>>To my mind, the key of Fruit strength is that the "Chess is the art of
>>>>>>exchange". So, Fabien's idea about flexible game stages looks to be a beautiful
>>>>>>way to improve positional play. Fruit can effectively consolidate the position.
>>>>>>It simply knows when to excange to improve position. I think that it's the main
>>>>>>key (cumulative with very good tuning of evaluation function). I think Fruit is
>>>>>>very perspective. The main line of progress for this project, to my mind, is to
>>>>>>add more complicated knowledge and intellectualize a search.
>>>>>>2) Rybka
>>>>>>Some time ago we discussed with Gian-Carlo Pascutto an idea of create special
>>>>>>"SET-tables" with sets of piece-square values indexed by 1) material on the
>>>>>>board; 2) king position; 3) pawn structure. Such tables can be calculated by
>>>>>>analyzing a lot of games. That time I delayed my work in this area because I
>>>>>>found other perspective things.
>>>>>>You can see that Rybka executable contains a lot of precalculated tables. And
>>>>>>also we all know that Rybka plays positional style. My version is that Rybka
>>>>>>uses some variation of SET-approach. At all cases it uses some precalculated
>>>>>>positional knowledge, but what sort of it? ;)
>>>>>My personal opinion:
>>>>>Fruit wins by 3 things: deep PV checking, mobility, and correctness.  I talked
>>>>>about this with Fabien at Reykjavik.  When you have mobility, you are very
>>>>>sensitive to being "driven back".  And when you can check your mainline 18-20
>>>>>ply and not lose any mobility, its very probably you're playing a good move.
>>>>>Rybka: I'm starting to think that a lot of Rybka's strength is tactical.  Try
>>>>>that baby out on a few test positions some time.  For example, the rapid TC CEGT
>>>>>list has Rybka 55 rating points ahead of Fruit, while the slower BFF list has
>>>>>Rybka only 15 rating points ahead of Fruit.
>>>>We need more data. I'll try to put it together when it's all ready.
>>>>One thing people tell me is that Rybka tends to stick with her moves from lower
>>>>depths more than other engines. This would also suggest better blitz play.
>>>I think that it may suggest simply that rybka is better because it needs less
>>>time to find the correct moves unlike other engines that need big depth to find
>>>the correct moves.
>>>I think that the only correct test is test with time handicap.
>>>I think that it may be interesting to see how much time programs need to get 50%
>>>against Rybka at 1 minute per game and the same for longer time control.
>>>I think that there is diminishing returns so if a program score better at blitz
>>>but wins at all time controls then it is not fair to claim that it is better
>>>blitz player.
>>>If you can prove that Rybka score 50% with time handicap of 3:1 at blitz against
>>>engine X(ponder off) and score less than 50% with the same time handicap at
>>>longer time control then you have a point.
>>Another topic we need some data about. Was it ever proven that engine
>>differences are magnified at shorter time controls? It's not obvious to me.
>I remember that there was some experiment with Fritz6 that showed diminishing
>returns and it also logical.
>Previous experiments also supported diminishing returns but the results were not
>I think that it is obvious that some opening lead to forced draw and it is going
>to be draw only if the sides search deep enough so after some time control there
>is 0 returns in these openings.
>It means that in order not to have diminishing returns you need to have opening
>with increasing returns.

In this case, there should be more draws at longer time controls.

This we can check very easily (although I am too lazy :)).


This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.