Author: Christophe Theron
Date: 08:45:20 07/14/00
Go up one level in this thread
On July 13, 2000 at 17:44:25, Dann Corbit wrote:
>On July 13, 2000 at 17:02:47, Christophe Theron wrote:
>[snip]
>>I understand your point.
>>
>>My feeling is that in the current state of the art, we are too much ignorant to
>>decide so easily what is knowledge (or chess wisdom) and what is not.
>>
>>Most people, when they use the words "chess knowledge", are thinking about
>>"position evaluation". I find this very short minded (I'm not saying you think
>>this way, of course).
>>
>>Position evaluation is not the only part of a chess program where you put "chess
>>knowledge". A lot of chess knowledge is put somewhere else in a chess program.
>>
>>There is a LOT of chess knowledge in the search algorithms. The concept of
>>recapture extension, for example, is pure chess knowledge. Move ordering is, as
>>well.
>
>Actually, I am forced to agree with you here. We might think also of a GM
>looking at the board. He is also performing a search, since he will consider
>several possibilities and choose the best one. He will have specific move
>ordering when he considers a particular move. I think that a big difference is
>that human players decide on a goal and then think about moves that aim towards
>achieving that goal.
That's right. When I try to use the knowledge of strong chess players (well at
least much stronger than myself), I always find this problem: most of the time
they evaluate MOVES not POSITIONS.
Of course they also know how to evaluate positions (but they are unable to give
numerical values to them, of course), but that's not how they "search" their
tree. They try to build "best lines" that have as many "good moves" in them as
possible.
One interesting thing that comes from this is: if it is possible to reach a
given position by two different paths (that's what we call a transposition),
they will almost always prefer one path over the other one.
A chess program would evaluate both lines as totally equivalent. A human player
would not.
That's why I think that human players are not using alphabeta actually. They are
using something close, but evaluating paths rather than final positions is
definitely not alphabeta.
>>They are both very related to chess, and quite unrelated. A grandmaster could
>>find these concepts useless maybe. But maybe a grandmaster is not a reliable
>>source of chess knowledge.
>>
>>Also, very often "knowledge" is associated with "memory" (storing data). This is
>>misleading as well. Most of the knowledge in a chess program exists in the form
>>of algorithms, not tables, databases or files.
>>
>>I tend to define knowledge (actually "relevant knowledge") as the set of
>>information processing procedures (algorithms) that help a given entity to
>>survive or even to grow in a given environment. Maybe I'm melting several
>>concepts together in this definition, but anyway these separate concepts are
>>really hard to differenciate. So maybe it is not so useful to differenciate
>>between them.
>
>I think that this is probably the most interesting area of chess program
>development. Struggling with ideas and definitions may spring forth something
>new.
Yes, and discovering a new algorithmic idea that works actually means
discovering something new about the nature of chess.
This is obvious for example with the idea behind "null move". The fact that
"zugzwang" is a very rare event in chess and that it allows to avoid a lot of
search effort is part of what makes the game interesting. All human players use
this idea without actually realizing what they are doing and why.
This property does not exist in other games such as checkers and
Othello/Reversi. This is as important as the fact that the chessboard is an 8x8
square. But it is less obvious, and not stated explicitely in the rules of
chess.
Christophe
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