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Subject: Re: One-reply extension howto

Author: Robert Hyatt

Date: 17:04:33 03/03/03

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On March 03, 2003 at 18:29:29, Sune Fischer wrote:

>It seems like a must-have extension, but with an incremental move generator how
>does one implement it?

You have two choices:

(1) if you do a "Legal move generator" that you use when getting out of check,
as I
do in Crafty, then you can notice it only produces one move and extend right
now.

(2) you can search each move generated, and when you search one that is not
flagged
as "illegal" (however you check that) save it and inc a counter.  When you are
done at
this ply, and the counter == 1, make that saved move, increment depth by
whatever
amount you want to extend, and search again.

I did it as (2) in Cray Blitz.  I do it as (1) in Crafty.

>
>Do you re-search at the end with +1 ply when you find there was only one move?
>
>Do you save it in hash so next time you know, or what..?

You can certainly do that.  I think DT/DB did...  I did in Cray Blitz.  I don't
now
since I generate moves when in check anyway and then use the hash move to pick
the best of the out-of-check moves, so I already know it is a one-move case or
not.

>
>-S.



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