Author: Christophe Theron
Date: 09:33:50 07/15/00
Go up one level in this thread
On July 14, 2000 at 16:18:24, Albert Silver wrote:
>On July 14, 2000 at 11:45:20, Christophe Theron wrote:
>
>>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.
>
>I don't know about that. It's true that many times a position can be transposed
>to via more than one move order, all the same, the trees involved are not the
>same, at least for humans. The problem is in limiting the size of the tree.
>Sure, in a given position I can begin a particular line with one move order that
>is more or less forcing, with a few branches to be calculated and a quiet move
>or two, or I can reach it with the very same moves, but in a different order. In
>one move order, some of the moves may require more calculations because of
>possibilities dependent on the move order. Suppose there are three checks that
>have only one or two direct possibilities, and I will also need two quiet moves
>that lead to the desired position and furthermore, there are two ways of doing
>this. In the first move order, I can interpose the quiet moves a bit earlier,
>but this also means that I have to take into account several possibilities,
>which may not work but that need to be calculated, that wouldn't be there if I
>were to first play the checks. Perhaps for the computer, the calculating
>necessary results in the same thing as it is more or less indifferent to many
>factors such as visual impressions, but not so for the human. I have seen this
>quite often in certain combinations, and I too will speak of the 'cleaner' move
>order as it leaves less doubts in its process. I learned this, and I agree with
>it.
>
>This also eventually leads to the more evolved form of handling positions, where
>players (human) choose the 'simpler' path. Again, this is highly debatable in
>theory as the 'simpler' solution can often be objectively longer, but this
>methodology is entirely human and was never designed for computers so while it
>may be debatable in theory, in practice it is not.
>
> Albert Silver
I did not say this approach was flawed. It might be used successfully for
computers one day, and maybe some good chess programs are already using the
idea, I don't know.
Christophe
>>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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