Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: a question to Tord about detecting threats in null move

Author: Uri Blass

Date: 09:47:23 10/03/03

Go up one level in this thread


On October 03, 2003 at 12:13:13, Anthony Cozzie wrote:

>On October 03, 2003 at 12:03:49, Uri Blass wrote:
>
>>
>>I can detect every big threat by adding a special search after making null move.
>>
>>For example if I like to detect threats of at least 2.2 pawns I can do
>>val=-alphabeta(depth-4,-beta+219,-beta+220,...)
>>
>>if (val<=beta-220)
>>threatmove[ply-1]=1;
>>//ply-1 because I still did not undo the null move.
>
>small error here: beta should be replaced by eval, or you will have massive
>instability problems.

If I am a queen down in the search and I threat to win a bishop then I do not
consider it as a threat  because a threat is a threat relative to beta.

I believe that Tord does the same(he replied that your example of threating the
queen twice by sacrificing material is solved by extending only big threats so
if you sacrifice a rook and a bishop the threat on the queen is not a big
threat).

I think that the idea that an extension should not be dependent on beta is a bad
idea.
It is better to have stronger engine with stability problems and not
weaker engine without them.

I prefer even not to care about using hash tables for pruning because my
experience told me that I cannot get significant gain there easily(I have a lot
of stuff that means that pruning or extension is not defined only by the
position).

Uri



This page took 0.14 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.