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Subject: Re: about using killers in Rebel and about programming

Author: Robert Hyatt

Date: 16:50:43 12/31/02

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On December 31, 2002 at 17:49:52, Uri Blass wrote:

>From Ed programmer stuff
>
>Killer-One [current ply]      110
>Killer-One [current ply-2]    108
>Killer-Two [current ply]      106
>Killer-Two [current ply-2]    104
>
>I until today used only
>
>Killer-One [current ply]
>Killer-Two [current ply]
>
>I am interested to know if using 4 killers is a new idea or maybe this idea is
>known to be used by other programs.

It was known in 1975.  Chess 4.0 used this.  You can find it mentioned in
the chess 4.7 chapter of "Chess Skill in Man and Machine."

We did that in Cray Blitz, but we also did more killers, going back to the
root in fact...



>
>I did try part of the idea that Ed suggested without clear results.
>
>I changed the order of moves in movei to
>
>Killer-One [current ply]
>Killer-One [current ply-2]
>Killer-Two [current ply]
>
>instead of
>
>Killer-One [current ply]
>Killer-Two [current ply]
>
>I found that it is better only in part of the cases and have not clear results
>if it is better or worse than previous order but I had a bug in the
>implementation and I checked killer[ply-2] even in cases when ply-2<0.
>
>It is surprising that the program did not crush and even performed better in
>part of the cases.
>
>I still do not use check bound software.
>I asked in a previous discussion about checking bounds but I solved the
>problem that caused me to ask about it and I also read a claim that if a
>varaible is out of bound the program should crush.
>
>I also looked for a software that will help me under visual C++ but after I
>asked to get it for free evaluation and I only got an email that suggest me to
>contact them by fax or telephone I did not respond(I responded by email but my
>email was blocked for some reason and I decided that the subject is probably not
>very important).
>
>I think now that it may be important because a chess program may even play well
>inspite of the fact that it calls killer[-1] so it is possible that I have more
>mistakes like that.
>

That probably won't hurt a thing.  That move probably would not pass your
legality check, so even a garbage move would just waste a tiny bit of time
as you notice it is not legal in the current position.



>I also see that the number of nodes in small depth also may be the same.
>
>Uri



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