Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: Unexpected problem with futility pruning ?

Author: Mridul Muralidharan

Date: 17:07:23 12/29/03

Go up one level in this thread


On December 29, 2003 at 18:16:39, Tord Romstad wrote:

>On December 29, 2003 at 16:01:08, Andrew Williams wrote:
>>I make sure that I have a legal move available before pruning stuff.
>
>This is good advice, and reminds me of an amusing bug I had in early versions of
>Gothmog
>(while I was still using normal futility pruning):  In positions which were so
>bad that all
>moves were pruned because they had no chance of bringing the score anywhere
>close,
>to alpha, the engine thought:  "I have no moves, but I'm not in check -- It's
>stalemate.
>Let's return 0".  As a result, the engine would sometimes make horrible
>blunders, and
>print out PVs where it sacrificed almost all its pieces, with a draw score at
>the end of
>the line.
>
>Tord

Ah ha !
One of the first ches playing versions of emss had the very same bug :)
So I have company ;)

Mridul



This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.