Author: Nobuhiro Yoshimura
Date: 15:58:12 10/25/98
Go up one level in this thread
On October 22, 1998 at 23:20:10, Robert Hyatt wrote:
>On October 22, 1998 at 23:04:31, Peter McKenzie wrote:
>
>>On October 22, 1998 at 21:38:29, Fawna Bergstrom wrote:
>>
>>>Well everyone has their opinions on this kind of question--here are a few of
>>>mine. Let's go back to basics:
>>>
>>>Level I: You search full-width to a fixed depth (alpha-beta, iterative
>>>deepening, etc. are all assumed, of course.) Here your evaluator includes both
>>>material and positional factors. Move ordering is critical. First expand
>>>"killer" moves, "interesting" moves and moves that yield a higher evaluation.
>>>
>>>Level II: If you like you can then search beyond that looking at "interesting"
>>>moves such as captures, threats, checks, etc. Don't bother with threats unless
>>>the threatened piece is hanging and/or more valuable than the threatening piece.
>>> You should limit the depth of this second phase or you can skip it altogether
>>>and go straight to level III--it's your call. In level II the evaluator >adjusts
>>>for material only. Personally I wouldn't waste too many plies on Level II.
>>
>>I'm not 100% sure what you mean here, but if you start returning scores from the
>> quiescence search that don't take into account changes in evaluation due to
>>captures effecting pawn structure, and these scores can find their way into your
>>PV, then you're likely to get killed positionally.
>>
>
>
>
>there are things interesting to try here. IE if you only look at winning
>captures, you can probably get away with a positional eval at the leaf node
>that starts the qsearch, and then pass this value along to be modified as
>pieces are captured.
>
May I ask a simple question ? I am a Japanese-Chess programmer so that
I donot much about the chess programming. In the following postion:
0) In the q-search node
1) WTM
2) a white in danger
Questions:
1) Do you generate esacaping moves for the white peice ?
2) Do you assume that a white piece can esacpe in the stand pat eval?
3) Is it better to make a "PASS" move ( without depth deductions)
to check whether the black can really gain profit by capturing it?
Nobuhiro
>Or, if you do like I once tried and look at even captures for say the first 4
>plies, then you could do positional evals until you stop doing even captures,
>then just pass the value along to be modified.
>
>IE you might get away with not doing full evals everywhere.
>
>but stopping evals at the leaf and doing lots of captures means you will likely
>end up with a wrecked pawn structure that is unavoidable..
>
>
>
>>>
>>>Level III: Beyond that you MUST look at checks by a side that isn't winning,
>>>moves that get out of check by a side that isn't losing, and captures of a >piece
>>>larger than the current material defecit, by a side that isn't winning. (For
>>>example, if it's White's move and she is a Knight down, look at a check or a
>>>rook capture but don't bother with any pawn captures. On the other hand, if
>>>it's White's move and she is already a rook up, then who cares if she can also
>>>capture the queen.) Examine large captures before smaller ones and checks last
>>>of all. This third phase has NO DEPTH LIMIT and adjusts for material only.
>>>Simple threats and other less-interesting moves are ignored in Level III.
>>
>>Its debatable whether its worthwhile looking at checks in the quiescence search.
>> Some do, some don't. My program looks at some checks early in the q-search
>>only.
>>
>>>
>>>Of course, none of these issues will do you any good if your program is not
>>>super-efficient. When you hit a "wall" and can't make any more conceptual
>>>improvements, then throw away every line of code and write a new super-optimal
>>>version. Examine public-domain source code for ideas to improve efficiency.
>>>
>>>I liked your question--very interesting topic.
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