Computer Chess Club Archives




Subject: Re: MTD(f) and hash table size

Author: Bo Persson

Date: 05:41:47 08/18/03

Go up one level in this thread

On August 18, 2003 at 07:24:46, Tord Romstad wrote:

>On August 17, 2003 at 15:08:12, Rudolf Huber wrote:
>>On August 17, 2003 at 14:09:19, Tord Romstad wrote:
>>>On August 17, 2003 at 04:27:06, Rudolf Huber wrote:
>>>>First scan you source files for occurences of alpha and beta.
>>>There are no alphas or betas left -- I rewrote search() and qsearch() from
>>>when implementing MTD(f).  I only have the single parameter (gamma), like in
>>>Aske Plaat's paper.
>>>>If you find any look hard and try to understand what you are doing there. In
>>>>mtd(f) there ist NO alpha and NO real beta. All the things (lazy eval?)
>>>>you do with alpha and beta are most likely wrong. Use the last score instead.
>>>What does the "last score" mean in the above sentence?
>>Yes, sorry. I mean the score from the previous iteration.
>I see!  Thanks for clarification.  This seems like an interesting idea;
>I will take a look at it.  Currently I am experimenting with tricks based
>on the values of the upper and lower bound in the search driver (an idea
>suggested by Andrew Williams).  A disadvantage is, of course, that often
>we only have one such bound.
>>You can also that score for lazy eval.
>Fortunately, I don't use lazy eval.  I am sure it would have given me a
>lot of headache when combined with MTD(f).

Yes! One "trick" here is to use the global bounds for the MTD driver to
determine lazy cutoffs, and not the very narrow alpha beta window of the current


Bo Persson

This page took 0.03 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.