Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: Repeatability (questions for Omid)

Author: Martin Giepmans

Date: 05:47:02 12/19/02

Go up one level in this thread


On December 19, 2002 at 01:46:01, Uri Blass wrote:

>On December 18, 2002 at 22:19:24, Martin Giepmans wrote:
>
>>On December 18, 2002 at 21:51:20, Omid David Tabibi wrote:
>>
>>>On December 18, 2002 at 21:44:09, Martin Giepmans wrote:
>>>
>>>><snip>
>>>>>>I don't understand what you are trying to say.
>>>>>>Without a research (if the verification search with reduced depth doesn't
>>>>>>give a cutoff) verification search would be pointless.
>>>>>
>>>>>The verification search goes deeper than the null-move search, so it might find
>>>>>tactical errors overlooked by the null-move search, and correct them (without
>>>>>any need for a re-search).
>>>>>
>>>>
>>>>No need for a research ??????????
>>>>It's late, I guess we are talking about two different things?
>>>
>>>No we aren't :-)
>>>
>>>When we have a fail-high report, we simply reduce the depth, and continue a
>>>regular search, as if nothing has happened. Because this regular search (which
>>>can be called verification search) goes deeper, it might find out threats beyond
>>>null-move search's horizon. In that case, you would get the correct result even
>>>if you don't do a re-search!
>>>
>>Yes, we _were_ talking about 2 different things :)
>>My thing is verification search, yours is what I would call "de-extension".
>>One difference is that de-extensions are symmetrical (you reduce depth for
>>both colors) while (standard) verification search is essentially asymmetrical.
>>
>>I think it's possible that at least some of the readers of your article
>>got confused here and implemented something in their programs that you
>>didn't intend. Perhaps that explains why in many cases your method didn't
>>seem to work.
>>
>>Martin
>
>I do not understand
>How can you reduce depth for only one color?
>
>There is only one varaible with the name depth in my program.
>
>Uri

That's right, but the effect is asymmetrical.
It's the same with nullmove.
Suppose a program has white and only uses nullmove on ply 2.
The effect is that it may overlook a good continuation for white, but
_not_ for black. Nullmove pruning is (in effect) asymmetrical.

Standard verification search (always research) is also asymmetrical.
If you leave out the research it becomes symmetrical: it may
overlook good continuations for _both_ sides.

I think there is a fundamental difference between vs with and without
research.

Martin









This page took 0.06 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.