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Larry Kaufman

Joined: 10 Jan 2010
Posts: 1229
Location: Maryland USA

Post subject: Re: stand pat or side to move bonus    Posted: Sun Mar 25, 2012 7:53 pm

bob wrote:
lkaufman wrote:
bob wrote:
 lkaufman wrote: In at least 99% of chess positions, it's better to be on move than not. Therefore all strong programs take this into consideration when evaluating positions or making decisions. There appear to be three possibilities: A. Simply give the side to move a bonus when doing an evaluation, which can either be a constant or may depend on something else. B. When reaching quies, if you are below beta but within for example 10 centipawns of beta allow the cutoff. C. Do both of the above. What are the pros and cons of the three methods? We currently use method A, but I notice that some strong programs appear to use B or C. Are there any other possibilities in use for handling this issue?

I've done this for a long time in Crafty. Current values are 5 and 8 for middle-game and endgame. I tested a bunch of different combinations, but those were best at the time. Not a huge gain anyway, but still, every Elo point counts...

I don't particularly see any difference in any of the above. If you add in the bonus, you may well cause a cutoff anyway. If you just check for the cutoff, you might save a little time.

Doing both seems redundant...

It's odd that you found that the value should go UP in the endgame, while both SF and Komodo found the opposite! I wonder why?
The difference between A and B is in whether the bonus affects only quies decisions (B) or all decisions thruout the search (A), for examply futility.

I don't think 5 centipawns is going to affect futility in any measurable way. As far as the difference, it makes sense to me actually. Where is the side to move more important, in the middlegame or when there are just kings on and a single tempo is often critical? I started with just one, and tuned it, then tried MG/EG and tuned each independently. 5/8 was best, but we are not talking 3-4-5 Elo here. This is very small.

I have been thinking about this wrongly. Forget about futility and other pruning. Here is the issue as I see it now. Since sometimes one must compare identical positions with opposite side-to-move in the search, there exists some stand pat value (or set of values) that when given to the side to move makes the two cases equally promising on average. Call this margin A. Now assume we don't do that. When reaching quiesce, we can accept the score or try for more with captures or checks. Let's assume there are no good captures or checks. Should we use the exact score, or the score plus some margin, B? Using a margin will give more cutoffs but may hurt quality if too high.
We have all been using just one margin for both purposes. But is there any particular reason to think that the optimum margin for purpose A is the same as the optimum one for purpose B? If not, which should be larger, A or B, and why?
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Subject Author Date/Time
Larry Kaufman Thu Mar 22, 2012 9:15 pm
Sam Hamilton Thu Mar 22, 2012 10:49 pm
Daniel Shawul Thu Mar 22, 2012 11:27 pm
Larry Kaufman Fri Mar 23, 2012 12:40 am
Daniel Shawul Fri Mar 23, 2012 1:27 am
Larry Kaufman Fri Mar 23, 2012 2:06 am
Daniel Shawul Fri Mar 23, 2012 3:07 am
Larry Kaufman Fri Mar 23, 2012 3:26 am
Richard Vida Fri Mar 23, 2012 2:07 pm
Larry Kaufman Fri Mar 23, 2012 2:42 pm
Richard Vida Sat Mar 24, 2012 9:59 am
Larry Kaufman Sat Mar 24, 2012 2:44 pm
Richard Vida Sun Mar 25, 2012 1:51 pm
Larry Kaufman Sun Mar 25, 2012 2:44 pm
Richard Vida Sun Mar 25, 2012 3:21 pm
Larry Kaufman Sun Mar 25, 2012 3:40 pm
Marek Kwiatkowski Fri Mar 23, 2012 2:46 pm
Richard Vida Fri Mar 23, 2012 2:01 pm
Robert Hyatt Fri Mar 23, 2012 2:38 pm
Larry Kaufman Fri Mar 23, 2012 2:47 pm
Uri Blass Fri Mar 23, 2012 3:39 pm
Larry Kaufman Fri Mar 23, 2012 3:45 pm
Robert Hyatt Sat Mar 24, 2012 3:03 am
Larry Kaufman Sat Mar 24, 2012 3:14 am
Robert Hyatt Sat Mar 24, 2012 4:41 am
Marco Costalba Sat Mar 24, 2012 8:12 am
Robert Hyatt Mon Mar 26, 2012 5:32 am
Sam Hamilton Mon Mar 26, 2012 2:12 pm
Robert Hyatt Sat Mar 24, 2012 3:00 am
Re: stand pat or side to move bonus Larry Kaufman Sun Mar 25, 2012 7:53 pm
Sune Fischer Sat Mar 24, 2012 10:38 am
Vincent Diepeveen Sun Mar 25, 2012 9:08 am
Uri Blass Sun Mar 25, 2012 11:24 am
Vincent Diepeveen Sun Mar 25, 2012 2:15 pm
Ed Schroder Sun Mar 25, 2012 1:02 pm
Larry Kaufman Sun Mar 25, 2012 7:43 pm
Ed Schroder Sun Mar 25, 2012 8:37 pm
Larry Kaufman Sun Mar 25, 2012 8:51 pm
Richard Vida Sun Mar 25, 2012 9:33 pm
Larry Kaufman Sun Mar 25, 2012 9:48 pm
Don Dailey Sun Mar 25, 2012 10:15 pm
Vincent Diepeveen Mon Mar 26, 2012 10:48 pm
Richard Vida Tue Mar 27, 2012 9:59 am
Vincent Diepeveen Tue Mar 27, 2012 11:38 am
Ed Schroder Sun Mar 25, 2012 10:39 pm
Larry Kaufman Sun Mar 25, 2012 3:49 pm
Vincent Diepeveen Sun Mar 25, 2012 4:20 pm
Larry Kaufman Sun Mar 25, 2012 4:47 pm

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