🚀 go-pugleaf

>From md85-epi@nada.kth.se Tue Jan 18 07:19:54 1994
Return-Path: <md85-epi@nada.kth.se>
Date: Tue, 18 Jan 94 14:13:53 +0100
From: md85-epi@nada.kth.se
Message-Id: <9401181313.AA20822@hemul.nada.kth.se>
To: mwhite@osiris.cso.uiuc.edu
Subject: Gnuchess, evaluation

I could not post this reply (device full).
If you would post it and maybe others in a summary I'd be most
grateful.

Your article/letter follows:
Newsgroups: gnu.chess
Subject: Re: Gnuchess fixed depth evaluations
Keywords: Gnuchess, evaluation
References: <2h7mvm$k3d@vixen.cso.uiuc.edu>
Organization: Royal Institute of Technology, Stockholm, Sweden

In <2h7mvm$k3d@vixen.cso.uiuc.edu> mwhite@osiris.cso.uiuc.edu (Dr Michael J. White) writes:

>Gnuchessers:

>I've noticed the following, and can find no explanation for this:

>Set the depth for gnuchess evaluations to, say, 6 ply.
>Now set post and go to evaluate a position.
>This should yield some score and a best move.

>Now in the new position, set the depth to one fewer ply, 5.
>Again, press "go" and watch for a score.
>Compare the new score with the old one.

>They're different!   Why?

There are some possibilities:

* GNU Chess chose parameters for the evaluation function depending
  on the current position.

* GNU Chess add a random number as part of the evaluation function.
  (This can be turned off)

* The evaluation function depend at least partly on the Alpha-Beta
  interval. If a fast approximation is outside the interval by a
  large enough margin, the slower evaluation is not used.

* The order of the moves depend on the killer move heuristic as well
  as the history heuristic. The order the game tree is searched
  depend on what has been searched before.

>This doesn't always happen.  The scores (accounting for
>who goes next times minus one) are usually within about 1/10
>of a pawn.  But shouldn't they be exactly the same?

I think my first reason is the most important one.

>By the way, book is off, transposition table is off.

You could turn random off too.

>Mike White

Urban Koistinen - md85-epi@nada.kth.se