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Subject: Re: Extend on Check

Author: Uri Blass

Date: 23:08:09 07/28/04

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On July 29, 2004 at 01:37:36, Volker Böhm wrote:

>Hi,
>
>what do you "extend" in quiescese, only "check-evades" (king is in check - all
>evades are done, not only captures) or checking moves (move that set king in
>check) too?
>
>What extends do you have you in total in normal search? (Make sure, that you
>NEVER add extensions to add more than one depth at one position).
>
>"Usual" Extend Algorithm for main search:
>
>DoMove(Position, Move)
>if (InCheck(Position)) Extend = 1; else Extend = 0;
>// Usually limit extensions to the double of RootDepth (Depth value at root)
>if (Ply + Depth + Extend > RootDepth * 2) Extend = 0;
>PosVal = -Search(Position, -Beta, -Alpha, Depth - 1 + Extend, !Wtm);
>UndoMove(Position, Move);
>
>Do you use the same algorithm?
>
>Greetings Volker

No
For example I never tried and do not use
if (Ply + Depth + Extend > RootDepth * 2) Extend = 0

If extend can get only 0 or 1 then the last rule is the same as:

If (Ply+Depth+1>RootDepth*2) Extend=0

If I understand correctly it means that you never search more than twice than
the nominal depth except qsearch.

Intuitively it does not seem to me a good idea and tactical ideas when you need
to search deeper can be important.

I think that it is better to try to find pruning tricks and not to limit the
extensions so even if it is today productive for movei because I still do not
use the right pruning tricks I do not plan to try the idea not to search deeper
than twice the nominal depth(except qsearch).

Uri



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