Author: Tony Werten
Date: 23:02:31 10/22/03
Go up one level in this thread
On October 23, 2003 at 00:24:45, Vincent Diepeveen wrote:
>On October 22, 2003 at 21:34:31, Anthony Cozzie wrote:
>
>>On October 22, 2003 at 21:00:52, Dave Gomboc wrote:
>>
>>>On October 22, 2003 at 14:40:23, Uri Blass wrote:
>>>
>>>>On October 22, 2003 at 13:13:37, Vincent Diepeveen wrote:
>>>>
>>>>>On October 22, 2003 at 06:30:13, Sergei S. Markoff wrote:
>>>>>
>>>>>>Hello All!
>>>>>>
>>>>>>DS - is a term for using some features of classical evaluation that consists of
>>>>>>two parts - material and positional.
>>>>>>There are a lot of positions in that for one side material evaluation is >0 but
>>>>>>positional evaluation is <0 or vice versa. The root of big part of mistakes made
>>>>>>by modern engines is underestimating of positional eval because the positional
>>>>>>evaluation is constructed of several "atomic" factors. The _sum_ of this factors
>>>>>>frequently isn't good positional evaluation (anyway there are a lot of
>>>>>>"palliative" methods to avoid this problem like evaluation the relationship
>>>>>>between several factors). We can't fully trust positional evaluation and that's
>>>>>>why most of modern programs using a small values for a lot of factors.
>>>>>
>>>>>In 1990 your statement would have been true.
>>>>>
>>>>>However in 2003, i know very little modern programs with small values for the
>>>>>positional factors. Perhaps diep is one of them in some sense, yet the quantity
>>>>>makes the total positional score overrule any material reality.
>>>>>
>>>>>>The idea of DS is to use disagreement between positional and material
>>>>>>evaluation. There are a lot of ways how to use it. For example we can check
>>>>>>nodes in which sum_eval < alpha, but positional eval is large (for example we
>>>>>>sacrificed a pawn for attack e.t.c.). For this nodes we can:
>>>>>>1. Rebuild quiescence to include checks e.t.c.
>>>>>>2. Extend search
>>>>>>3. Change eval for the case of losing pawn or quality (trade bishop or knight
>>>>>>for rook) for big passed pawn / king attack eval.
>>>>>>4. Do assymetric eval.
>>>>>>5. Something else?
>>>>>>
>>>>>>Do you have some ideas in this area?
>>>>>
>>>>>In case you forgot, the evaluation can just return 1 score and that's a total
>>>>>score it can't return 2 scores for either positional or tactical matters.
>>>>
>>>>I do not think that sergei forgot something.
>>>>He is a good programmer and smarthink is one of the best free engines.
>>>>
>>>>The fact that the evaluation can return only one score does not mean that the
>>>>program cannot compute more than one score to get decisions because decisions
>>>>are not only about evaluation but also about which lines to extend.
>>>>
>>>>Uri
>>>
>>>There's no law that says a score must be scalar.
>>>
>>>Dave
>>
>>
>>I just had a vision of a program that returned tensors in its eval. Hmm.
>>
>>I'm with Sergei on this one though - Zappa already keeps track of the various
>>"parts" of the eval, so I can tell if the position has a high kingsafety score
>>for white or some such.
>>
>>anthony
>
>Sure, but that's not the point.
>
>A year or 5-7 ago i had the idea that i should seperate some scores. So i
>returned 2 values to the search algorithm.
>
>My score was roughly said (but more interesting labels):
>
> struct Score { int value1; int value2; };
>
>The point is HOW to use this for search.
>
>I figured out after not a too long time that i had to use 1 score to combine the
>2 scores to 1 score anyway or you can never give a cutoff.
>
>So my viewpoint is that sooner or later you must trigger a decision and use the
>alfabeta features of the search.
>
>So why not do that directly and just return 1 score.
>
>Extensions have nothing to do with this.
I think that you're talking about something a lot more complicated. You are
talking about returning 2 (or more) scores from search ( wich, after some
attemps, I concluded cannot be done in alphabeta)
He seems to be only talking about returning 2 scores from eval, or at most, 1
from search and 1 from eval.
So 1 "full" score from either search or a "full" eval, and then compare this
with fe a material only eval.
I think most people use this already. ie "If my opponents kingsafety is bad, and
I'm not more than 1 piece behind, then extend" would fall into this category.
Tony
>
>Best regards,
>Vincent
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