Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: Forward pruning and PVS, was Re: Interesting mate test for hashing,

Author: Robert Hyatt

Date: 17:58:56 09/12/99

Go up one level in this thread


On September 12, 1999 at 16:58:52, Alessandro Damiani wrote:

>On September 12, 1999 at 10:17:42, Robert Hyatt wrote:
>
>>On September 12, 1999 at 06:38:23, Alessandro Damiani wrote:
>>
>>>On September 11, 1999 at 22:25:24, Robert Hyatt wrote:
>>>
>>>>On September 11, 1999 at 17:48:55, Alessandro Damiani wrote:
>>>>
>>>>>On September 11, 1999 at 15:59:19, Ed Schröder wrote:
>>>>>
>>>>>>On September 11, 1999 at 15:36:18, Robert Hyatt wrote:
>>>>>>
>>>>>>>OK... then we are 'in sync' here it seems..
>>>>>>>
>>>>>>>As far as PVS, the main advantage is that since almost everything is searched
>>>>>>>with a null-window, it saves nodes, _IF_ you do well at move ordering (I have
>>>>>>>no doubt that you do well so PVS might be a win for you too)...
>>>>>>>
>>>>>>>It reduced my trees by 10% and loses nothing at all...  unless you screw
>>>>>>>up move ordering, then it can make the tree bigger as you first search with
>>>>>>>a null window, then you have to re-search with the normal window...
>>>>>>
>>>>>>Thus, PVS is aspiration search with a null-window? Is that all there is?
>>>>>>
>>>>>>Ed
>>>>>
>>>>>I think there is problem with the combination null-window and forward pruning:
>>>>>forward pruning is not perfect. So there are more wrong cut-offs with PVS than
>>>>>without. This could affect positional play.
>>>>>
>>>>>Alessandro
>>>>
>>>>
>>>>I don't do forward-pruning at all. Other than the sort of similar idea that
>>>>comes out of null-move search with R=2...
>>>
>>>But null-move is not perfect, too. So there are wrong cut-offs, mainly after
>>>quiet moves.
>>>
>>>Alessandro
>>
>>
>>I would _never_ argue with that.  :)
>>
>>It _definitely_ produces problems in the right kinds of positions. It sort of
>>reminds me of banging your head against a brick wall for several minutes.  The
>>only reason you would do that is because it feels _so good_ when you stop.  Null
>>move is sort of like that...
>>
>>:)
>
>What I mean is that you use R=2 and not R=1. There is a difference in accuracy.
>
>Alessandro


yes there is.. and I am actually not using R=2 (for the last year or so in
fact.)  I use R=3 near the root, R=2 near the leaf positions.  And yes, this
has an accuracy issue.  It also has a speed issue, and head-to-head testing
says that R=2 will beat R=1 by a statistically significant margin.



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.