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Lucas Braesch

Joined: 31 May 2010
Posts: 1824

Post subject: Re: futility pruining, razoring question    Posted: Fri Apr 06, 2012 7:22 am

mcostalba wrote:
Well, clearly razoring has no sense in PV (even theoretically) . Near leaves of PV you expect value to be above alpha, and in case you find a fail low at next iteration you really don't want to find it through razoring. But I suspect Bob was referring to something else than all of us: normally I use chessprogramming as a name reference, but I think he is using other references and probably with 'razoring' he is referring to forward pruning or something like that.

Regarding Luca's code I find this:

 Code: const int score = qsearch(B, alpha, beta, 0, ply+1, is_pv, si+1);

a really optimistic assumption, normally you want to verify with a reduced margin, not with alpha. If this was also in your original code, perhaps could be a reason why it didn't work for you and so you switched to a kind of reduction instead of pruning.

You're right. As pointed out by Martin, I got fooled by the chess programming wiki
I'm currently testing this alternative:
 Code: if (UseRazoring && depth <= RazorDepth       && !is_pv && !is_mate_score(beta) && !in_check)    {       if (current_eval + RazorMargin(depth) <= alpha) {          const int score = qsearch(B, alpha, beta, 0, ply+1, is_pv, si+1);          if (score + RazorMargin(depth) <= alpha)   //**             return score;       }    }

I've just ran 1000 games in 6"+0.1", and it scored 52% against my previous code. Thanks for the tip!
 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
Subject Author Date/Time
Marco Belli Wed Apr 04, 2012 6:21 pm
Robert Hyatt Thu Apr 05, 2012 7:07 pm
Karlo Bala Jr. Thu Apr 05, 2012 7:59 pm
Vincent Diepeveen Thu Apr 05, 2012 11:47 pm
Lucas Braesch Fri Apr 06, 2012 3:34 am
Martin Sedlak Fri Apr 06, 2012 3:35 am
Martin Sedlak Fri Apr 06, 2012 4:10 am
Martin Sedlak Fri Apr 06, 2012 5:15 am
Marco Costalba Fri Apr 06, 2012 5:45 am
Re: futility pruining, razoring question Lucas Braesch Fri Apr 06, 2012 7:22 am
Martin Sedlak Fri Apr 06, 2012 7:30 am
Lucas Braesch Fri Apr 06, 2012 8:36 am
Marco Costalba Fri Apr 06, 2012 11:42 am
Lucas Braesch Fri Apr 06, 2012 1:21 pm
Ricardo Barreira Fri Apr 06, 2012 3:00 pm
Vincent Diepeveen Fri Apr 06, 2012 5:21 pm
Lucas Braesch Sat Apr 07, 2012 1:59 am
Vincent Diepeveen Sat Apr 07, 2012 8:22 am
Marco Costalba Sat Apr 07, 2012 9:52 am
Vincent Diepeveen Sat Apr 07, 2012 1:53 pm
Ed Schroder Sat Apr 07, 2012 3:46 pm
Vincent Diepeveen Sat Apr 07, 2012 4:07 pm
Lucas Braesch Sun Apr 08, 2012 3:08 am
Vincent Diepeveen Sun Apr 08, 2012 10:12 am
Matthew R. Brades Sun Apr 08, 2012 11:18 am
Marco Belli Mon Apr 09, 2012 7:42 pm
Marco Belli Mon Apr 09, 2012 8:23 pm
Martin Sedlak Mon Apr 09, 2012 9:04 pm
Marco Belli Mon Apr 09, 2012 9:24 pm
Marco Belli Tue Apr 10, 2012 10:52 am
Martin Sedlak Tue Apr 10, 2012 11:58 am
John Merlino Sat Apr 07, 2012 5:10 pm
Vincent Diepeveen Sat Apr 07, 2012 5:41 pm
John Merlino Sat Apr 07, 2012 5:54 pm

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