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Subject: Re: Question for Hyatt about Alpha/Beta

Author: Vasik Rajlich

Date: 08:25:16 02/06/04

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On February 06, 2004 at 10:54:23, José Carlos wrote:

>On February 06, 2004 at 10:41:21, Vasik Rajlich wrote:
>
>>On February 06, 2004 at 10:27:48, José Carlos wrote:
>>
>>>On February 06, 2004 at 09:07:17, Anthony Cozzie wrote:
>>>
>>>>On February 06, 2004 at 06:26:20, Uri Blass wrote:
>>>>
>>>>>On February 06, 2004 at 05:54:29, Vasik Rajlich wrote:
>>>>>
>>>>>>On February 06, 2004 at 03:42:42, Uri Blass wrote:
>>>>>>
>>>>>>>On February 06, 2004 at 02:15:35, Tord Romstad wrote:
>>>>>>>
>>>>>>>>On February 05, 2004 at 15:15:47, Uri Blass wrote:
>>>>>>>>
>>>>>>>>>I think that you underestimate your engine.
>>>>>>>>>It seems to get similiar depth to crafty.
>>>>>>>>>
>>>>>>>>>For example in the following position it got depth 11 even in blitz 4+2
>>>>>>>>
>>>>>>>>Yes, 11 plies in blitz games is not unusual.  But 11 plies in Gothmog and 11
>>>>>>>>plies in Crafty is not the same.  I do much more forward pruning and depth
>>>>>>>>reductions than Bob, and fewer extensions.  In non-tactical positions like
>>>>>>>>the one you give, my qsearch is also considerably smaller than Bob's (I think).
>>>>>>>>
>>>>>>>>Tord
>>>>>>>
>>>>>>>I do not think that there is a big difference.
>>>>>>>Crafty searches bigger tree because it searches more irrelevant lines.
>>>>>>>
>>>>>>>I guess that the main advantage of Crafty relative to Gothmog when you use one
>>>>>>>processor is superior evaluation(Gothmog's evaluation is more complex but bigger
>>>>>>>is not always better and not having  bugs or some too optimistic scores of
>>>>>>>gothmog that lead to wrong sacrifices can be more important and it is possible
>>>>>>>that Gothmog can get crafty level if you only reduce the big positional scores
>>>>>>>that encourage it to sacrifice).
>>>>>>>
>>>>>>>I do not think that gothmog see less than crafty in the relevant lines(crafty
>>>>>>>has bigger tree but it proves nothing).
>>>>>>>I know that test suites are no proof but results of the gcp test suite give me
>>>>>>>the impression that cases when Gothmog can see more than crafty are not rare.
>>>>>>>
>>>>>>>Uri
>>>>>>
>>>>>>I have the theory that the greater your search resources (ie combination of time
>>>>>>and hardware), the less important is the search, and the more important is the
>>>>>>evaluation.
>>>>>
>>>>>I do not agree with that theory.
>>>>>
>>>>>For example suppose a program has no tablebases.
>>>>>
>>>>>With deep search it may not need knowledge how to win KQ vs K when with small
>>>>>search it may need the knowledge.
>>>>>
>>>>>If the hardware is fast enough the program can solve the game with only piece
>>>>>square table evaluation.
>>>>>
>>>>>Of course we are not going to see it but with good hardware evaluation what win
>>>>>is better in some endgames become unimportant because the program will not fail
>>>>>to win thanks to search.
>>>>>
>>>>>Uri
>>>>
>>>>Vas's point is this (and its the same reason Zappa is a relatively weak engine
>>>>tactically):
>>>>
>>>>If you are playing at 40 / 2 on a quad opteron, do you care how many WAC
>>>>positions you can solve in 1 second?
>>>>
>>>>anthony
>>>
>>>  Why not? Move WAC positions down inside the search tree instead of thinking of
>>>them only as root positions. Solving them quickly at the root means seing the in
>>>advance in longer time controls.
>>>
>>>  José C.
>>
>>The stakes are much higher at the root. Overlook a possible tactic at the root,
>>or play a move (at the root) which walks into a tactic, and you just cost
>>yourself somewhere around half a point. No improvement in positional play will
>>make up for that. Overlook a tactic four moves in which makes it possible to
>>play some good positional move and you cost yourself maybe 1/200th of a point.
>>
>>It's a question if you accept that some extensions/reductions are good for
>>tactics and bad for positional play.
>>
>>Vas
>
>  My answer was directed to:
>>>>If you are playing at 40 / 2 on a quad opteron, do you care how many WAC
>>>>positions you can solve in 1 second?
>
>  To answer you: a certain root position was a leaf node some moves before.
>Tactics are importante everywhere in the tree. The 1/200th thing I don't
>understand what you mean.
>
>  José C.

By 1/200th I am talking about the price of being wrong. If you overlook a tactic
which starts on ply 5 of some quiet positional line, then you will be missing
the chance to play something possibly slightly better positionally, or you will
play into some line and next move you will have to head into a different
variation. The cost may be (statistically) 1/200th of a point, ie you chance to
win may go from 55.5% to 55.0%. In this case, it may no longer be worth it
extending forcing tactical lines just to find these tactics, at the cost of
positional search.

Vas



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