Author: Christophe Theron
Date: 21:21:23 07/07/02
Go up one level in this thread
On July 07, 2002 at 23:53:16, Robert Hyatt wrote:
>On July 07, 2002 at 23:42:03, Omid David wrote:
>
>>On July 07, 2002 at 21:43:47, Robert Hyatt wrote:
>>
>>>On July 07, 2002 at 16:47:33, Omid David wrote:
>>>
>>>>On July 07, 2002 at 16:36:57, Robert Hyatt wrote:
>>>>
>>>>>On July 07, 2002 at 11:48:27, Omid David wrote:
>>>>>
>>>>>>On July 06, 2002 at 23:23:28, Robert Hyatt wrote:
>>>>>>
>>>>>>>On July 06, 2002 at 22:29:44, Omid David wrote:
>>>>>>>
>>>>>>>>On July 06, 2002 at 10:20:17, Robert Hyatt wrote:
>>>>>>>>
>>>>>>>>>On July 06, 2002 at 01:07:36, Ricardo Gibert wrote:
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>Okay, but so what?
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>So perhaps the idea of "forward pruning" is foreign to us as well...
>>>>>>>>>>
>>>>>>>>>>I see no logical difference between deciding which moves are interesting and
>>>>>>>>>>worth looking at and deciding which moves are not interesting and not worth
>>>>>>>>>>looking at. It looks to me like 2 sides of the same coin, so your speculation
>>>>>>>>>>that "perhaps the idea of "forward pruning" is foreign to us as well..." does
>>>>>>>>>>not seem to be of any consequence.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>However, that has been _the point_ of this entire thread: Is DB's search
>>>>>>>>>inferior because it does lots of extensions, but no forward pruning. I
>>>>>>>>>simply said "no, the two can be 100% equivalent".
>>>>>>>>
>>>>>>>>Just a quick point: The last winner of WCCC which *didn't* use forward pruning
>>>>>>>>was Deep Thought in 1989. Since then, forward pruning programs won all WCCC
>>>>>>>>championships...
>>>>>>>
>>>>>>>
>>>>>>>In 1992 no "supercomputer" played. In 1995 deep thought had bad luck and lost
>>>>>>>a game it probably wouldn't have lost had it been replayed 20 times. No
>>>>>>>"supercomputer" (those are the programs that likely relied more on extensions
>>>>>>>than on forward pruning due to the hardware horsepower they had) has played
>>>>>>>since 1995...
>>>>>>>
>>>>>>>I'm not sure that means a lot, however. IE I don't think that in 1995 fritz
>>>>>>>was a wild forward pruner either unless you include null move. Then you
>>>>>>>would have to include a bunch of supercomputer programs including Cray Blitz
>>>>>>>as almost all of us used null-move...
>>>>>>
>>>>>>I personally consider null-move pruning a form of forward pruning, at least with
>>>>>>R > 1. I believe Cray Blitz used R = 1 at that time, right?
>>>>>
>>>>>
>>>>>I believe that at that point (1989) everybody was using null-move with R=1.
>>>>>It is certainly a form of forward pruning, by effect.
>>>>
>>>>Yes, and today most programs use at least R=2... The fact is that new ideas in
>>>>null-move pruning didn't cause this change of attitude, just programmers
>>>>accepted taking more risks!
>>>
>>>
>>>I think it is more hardware related. Murray Campbell mentioned R=2 in the
>>>first null-move paper I ever read. He tested with R=1, but mentioned that
>>>R=2 "needs to be tested". I think R=2 at 1980's speeds would absolutely
>>>kill micros. It might even kill some supercomputers. Once the raw depth
>>>with R=2 hits 11-12 plies minimum, the errors begin to disappear and it starts
>>>to play reasonably. But at 5-6-7 plies, forget about it.
>>
>>So using a fixed R=3 seems to be possible in near future with faster hardware,
>>doesn't it?
>
>
>Very possibly. Or perhaps going from 2~3 as I do now to 3~4 or even 4~5 for
>all I know... I should say that going from 2 to 3 is not a huge change. Bruce
>and I ran a match a few years ago with him using Ferret vs Crafty with Ferret
>using pure R=2, and then pure R=3. We didn't notice any particular difference
>at that time. It played about the same, searched about the same depth, etc...
Increasing R is pointless after 3.
Because instead of having a null move search using 5% of your time (just an
example, I do not know the exact value), it will use only 2% or 3%.
The speed increase is ridiculous, and the risks are getting huge.
The only thing you can get by increasing R after that is having a percentage of
search spent in null move close to 0. So a potential of 2% or 3% increase in
speed.
And an big potential to overlook easy combinations everywhere in the tree.
That's why I believe that working on R>3 is a waste of time.
Christophe
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