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Subject: Re: Question for Hyatt about Alpha/Beta

Author: José Carlos

Date: 07:54:23 02/06/04

Go up one level in this thread


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.



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