Computer Chess Club Archives




Subject: real job of the qSearch? find quiet vs stop horizon effect

Author: scott farrell

Date: 07:18:56 08/28/03

When you read most literature it says "to find quiet positions" so the eval
function is more accurate, and the quiescent in the name suggests the same. But
I think this is wrong, and most people use it for the later.

Here are things I and other have put in/out/in/out of their qSearches:
- capture by LVA and SEE
- checks
- passed pawns

And as we but more into the qSearch, in an effort to stop spending too much
nodes on it, we try:
- pruning
- stand pat - ala Crafty
- etc

The whole idea of getting to the next ply is to reveals horizon errors and such
in the current ply.

I have a few positions where a black pawn cant be stopped because of wrong
colour bishop, and a white pawn similarly close and supported and attacked by
bothKings and will never score a try. For the main search it just keeps
horizoning the fact that one pawn is unstoppable. (maybe I need to knowledge for
this instead of search). As soon as I put passed pawn in qSearch, it sees this
in about 6 plies, whereas before it needs something like 15 plies (to exhaust
its best efforts at horizoning it). Checks in the qsearch fall into the same
pile, whereas captures are different. Extensions dont seem to help the
horizoning problem, only the qSearch.

So it is the qSearch's job to find quiet or to stop some classes of horizon

A few threads down, you'll see Robert's note about QxP on the last node, and the
next iteration obviously sees the folly with PxQ. Good captures in the asearch
grab this easily, and I think was the original intent of the qsearch as the
oustanding PXQ is HOT and not quiet.



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