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Robert Hyatt

Joined: 27 Feb 2006
Posts: 15817
Location: Birmingham, AL

Post subject: Re: optimal aspiration window for stockfish question    Posted: Wed Mar 14, 2012 10:18 pm

Don wrote:
mcostalba wrote:
 Rebel wrote: I am sure the SF team have done considerable testing here.

Yes, we have.

At the end of endless trials with differnt formulas and values we end up in starting with a small window value:

 Code: delta = Value(16); alpha = RootMoves[PVIdx].prevScore - delta; beta  = RootMoves[PVIdx].prevScore + delta;

That is increased after a fail low/high with the following formula:

 Code: if (bestValue >= beta) {     beta += delta;     delta += delta / 2; } else if (bestValue <= alpha) {        alpha -= delta;     delta += delta / 2; }

I want to add that this is the Ippo* formula and I think that very probably it is what is used in _all_ the top engines from Rybka 3 to Houdini. Although we knew the Ippo formula since when sources were published we moved to that only one year later, after having tried all the possible different combinations: some are weaker, some are equivalent ELO wise, but more complex, so this is the simplest formula (we know) that guarantees top performance.

Answering to Uri: I am not interested in tweaking the engine on a sample position. I only use real games to validate a change.

That's what we do. We will run a few hundred games at various fixed depth levels and have the instrumentation that gives us the average time per move up to some arbitrary move number. I think we currently use move 70. We think this is superior to just running 100 positions and timing them. We only do this when we want data on something that is supposed to be a speedup - normally we just run time games to measure general improvements and things that involve trade-offs.

Since it was a trivial change, I took the above and rewrote it to fit Crafty's search. Absolutely no change, either up or down. A couple of things I do not like about it however. 1. Several re-searches to win a pawn or more, and 2. way too many re-searches to find a forced mate.

We've used several different approaches. In Cray Blitz we did more "bumps". In Crafty I settled on fewer. But it actually doesn't seem to matter one bit based on the testing I just did, which was run at fast games and at 1min+1sec games as well. Absolutely no +/- change when switching from what I did to this, and back...
 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
Subject Author Date/Time
Uri Blass Mon Mar 12, 2012 11:14 am
Ed Schroder Mon Mar 12, 2012 12:55 pm
Marco Costalba Mon Mar 12, 2012 6:47 pm
Don Dailey Mon Mar 12, 2012 9:41 pm
Re: optimal aspiration window for stockfish question Robert Hyatt Wed Mar 14, 2012 10:18 pm
Marco Costalba Thu Mar 15, 2012 6:15 am
Robert Hyatt Thu Mar 15, 2012 2:06 pm
Robert Hyatt Thu Mar 15, 2012 5:30 pm
Robert Hyatt Thu Mar 15, 2012 8:11 pm
Robert Hyatt Thu Mar 15, 2012 9:55 pm
Miguel A. Ballicora Thu Mar 15, 2012 10:23 pm
Robert Hyatt Fri Mar 16, 2012 3:29 am
Robert Hyatt Fri Mar 16, 2012 3:41 am
Rémi Coulom Fri Mar 16, 2012 8:38 am
Robert Hyatt Fri Mar 16, 2012 5:20 pm
Karlo Bala Jr. Fri Mar 16, 2012 11:30 am
Robert Hyatt Fri Mar 16, 2012 5:26 pm
Ed Schroder Fri Mar 16, 2012 6:31 pm
Robert Hyatt Fri Mar 16, 2012 7:16 pm
Vincent Diepeveen Sat Mar 17, 2012 1:44 pm
Robert Hyatt Sat Mar 17, 2012 4:11 pm
Marco Costalba Sat Mar 17, 2012 5:28 pm
Robert Hyatt Sun Mar 18, 2012 3:28 am
Lucas Braesch Sun Mar 18, 2012 5:55 am
Joona Kiiski Sun Mar 18, 2012 9:02 am
Robert Houdart Mon Mar 12, 2012 10:44 pm
Robert Houdart Tue Mar 13, 2012 9:18 am
Uri Blass Tue Mar 13, 2012 10:12 am
Karlo Bala Jr. Wed Mar 14, 2012 7:46 pm
Robert Hyatt Thu Mar 15, 2012 9:49 pm
Lucas Braesch Wed Mar 14, 2012 4:10 pm
Eelco de Groot Wed Mar 14, 2012 7:30 pm
Lucas Braesch Thu Mar 15, 2012 2:03 am
Marco Costalba Thu Mar 15, 2012 6:13 am
Eelco de Groot Tue Mar 13, 2012 10:20 am
Uri Blass Tue Mar 13, 2012 12:57 pm

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