Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: Nalimov TB question

Author: Bas Hamstra

Date: 12:58:33 11/12/01

Go up one level in this thread


On November 12, 2001 at 15:22:39, Heiner Marxen wrote:

>On November 12, 2001 at 08:14:32, Gian-Carlo Pascutto wrote:
>
>>On November 12, 2001 at 06:59:51, Bas Hamstra wrote:
>>
>>>On November 12, 2001 at 04:46:19, Gian-Carlo Pascutto wrote:
>>>
>>>>On November 11, 2001 at 19:42:29, Bas Hamstra wrote:
>>>>
>>>>>Is there any documentation about linking Nalimov?
>>>>
>>>>probe.txt, which comes with the generator
>>>>
>>>>>I am not sure what score a probe() should return. I set up a FINE that is a mate
>>>>>in 23 (verified on nalimov's online TB site). However, when my probing function
>>>>>returns 32756. Some debugging in TBIndex.cpp learns that initially it found 113
>>>>>that is then converted to 32756 by macro S_to_L. Doesn't seem right. Shouldn't
>>>>>it just return the number of moves to mate eventually? Peeking in Crafty seems
>>>>>to indicate so.
>>>>
>>>>I figured out the conversion formula by setting up some positions
>>>>and looking at the values I got back until I figured it out.
>>>>
>>>>In Sjeng, it looks like this:
>>>>
>>>>if (tbScore == bev_broken) return KINGCAP;
>>>>
>>>>  EGTBHits++;
>>>>
>>>>  if (tbScore > 0)
>>>>  {
>>>>        return ((tbScore-bev_mi1)*2+INF-ply-1);
>>>>  }
>>>>  else if (tbScore < 0)
>>>>  {
>>>>        return ((tbScore+bev_mi1)*2-INF+ply);
>>>>  }
>>>>  return 0;
>>>
>>>Hi GianCarlo,
>>>
>>>I saw this in Crafty too. But that doesn't give me a realistic value at all.
>>>However if I use L_bev_mi1 (like in ExChess) in stead it comes more in the right
>>>direction. But that gives me a M13 in stead of the M23.
>>>
>>>(I checked in TBIndex.cpp the right squares are found)
>>>
>>
>>M23 = ((M13-1)*2)-1
>>
>>If you compare this to the formula above you will see it is similar.
>>
>>I'm sorry I cannot be of more help, but I think the best thing
>>to do is not to try to figure out how other formulas work (depends
>>too much on how you represent mate scores in your program), but
>>to set up a few positions where you know what the score should be,
>>and look at what the probing function gives you back.
>>
>>By comparing the two, it should not be hard to arrive at the correct
>>formula for your program. At least, thats how I did it :)
>>
>>--
>>GCP
>
>Here is the relevant part from Chest:
>
>    v = L_TbtProbeTable(iTb, side, ind);
>    XDB(1,  printf("= eg_probe v=%d\n", (int)v); )
>    /*
>     * Now, we must translate back that value into a value,
>     * which we understand...
>     */
>    if( v == L_bev_broken ) {
>        scinc(egsc.prob_broken);
>        q = EGQ_DUNNO;
>    }else if( v == L_bev_draw ) {
>        scinc(egsc.prob_draw);
>        q = EGQ_DRAW;
>    }else if( v > 0 ) {                 /* wins */
>        /*
>         * Deeper wins have smaller values.
>         */
>        scinc(egsc.prob_wins);
>        q = EGQ_WINS_Q(1 + (L_bev_mi1 - v));
>    }else {                             /* lost */
>        /*
>         * Deeper losses have larger values (less negative).
>         */
>        scinc(egsc.prob_loss);
>        q = EGQ_LOST_Q(v - L_bev_li0);
>    }
>    XDB(1,  printf("< eg_probe q=%d\n", (int)q); )
>    return q;
>
>EGQ_WINS_Q(N) codes "mate in N"
>EGQ_LOST_Q(N) codes "is followed by mate in N"
>
>L_bev_mi1  == "mate in 1"
>L_bev_li0  == "lost in 0"
>
>That should be a usable starting point.
>
>Heiner

Thanks guys, figured it out. As always, it was something stupid.

Bas.





This page took 0.1 seconds to execute

Last modified: Thu, 07 Jul 11 08:48:38 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.