Game Theory - Perfect Strategy?

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Avatar of Elroch

There is generally a trade-off between computing time and storage capacity in computation. For example, the tablebase of chess is a hypothetical database (impractical on account of its astronomical size) which allows instant determination of the evaluation of all possible moves in a position.

At the other extreme it is possible (easy, in fact)  to write a tiny program that uses a small amount of memory which could evaluate all the possible moves in any position, with the only problem being that the calculation for a position usually takes longer than the age of the Universe.

Avatar of efintushel

The history of the (moves of) a game is irrelevant in adjudicating any given position.

Chess is clearly a two-person zero sum game, so it has an optimum strategy--I think Von Neumann proved this with an analogy to spherical geometry.

Nobody knows if it is optimally a win for white or for black, or a draw, and I don't think players' consensus matters on this point. For example, when the tables for a crertain set of endgames was actually computed some years ago, there were found endings previously universally considered draws that, in fact, were wins--though the winning sequence was tactically incomprehensible to any human.

Avatar of efintushel

By the way, someone upstream gave the wrong number of opening moves in tic-tac-toe. Because of the symmetries, there are only three: corner, middle, or side.  (I think the earlier poster mistakenly said that there were six!)

Avatar of Elroch
efintushel wrote:

The history of the (moves of) a game is irrelevant in adjudicating any given position.

While the rest of your post was correct, this is an error. The value of a position in competition rules chess (eg FIDE, USCF) can depend crucially on:

  1. the ply count since the last irreversible move
    and
  2. which positions have been previously visited twice

To understand the latter, consider the case where there is a single path to a win, but that path goes through a position that has been visited twice.

 

Avatar of tygxc

@107

"The history of the (moves of) a game is irrelevant in adjudicating any given position.
this is definitely an error." ++ No, it is not an error.

"The value of a position in competition rules chess (eg FIDE, USCF) can depend crucially on:
the ply count since the last irreversible move and which positions have been previously visited twice" ++ Visiting the same position twice can always be avoided. The 50-moves rule is never triggered with perfect strategy i.e. optimal play from the initial position.

Avatar of Elroch
tygxc wrote:

@107

"The history of the (moves of) a game is irrelevant in adjudicating any given position.
this is definitely an error." ++ No, it is not an error.

"The value of a position in competition rules chess (eg FIDE, USCF) can depend crucially on:
the ply count since the last irreversible move and which positions have been previously visited twice" ++ Visiting the same position twice can always be avoided. The 50-moves rule is never triggered with perfect strategy i.e. optimal play from the initial position.

Now you are just making yourself look foolish.

Adjudication only occcurs in real games between real players and definitely can depend on the history of the play. If it could not, certain rules would be unnecessary! [It is mostly a historical curiosity, as rapid finishes have become the norm].

As a specific example, in a real game if a position has been repeated twice and one player loses if they don't repeat the position a third time on the next move, the position has to be adjudicated a draw.  By contrast the same basic chess position is a win for the other side.

Perhaps you got confused and thought the post was about the abstract game?

Avatar of tygxc

@109
"Perhaps you got confused and thought the post was about the abstract game?"
++ The title of the thread is: Game Theory - Perfect Strategy?
If one player can win a position, then the perfect strategy is not to repeat positions twice.

Avatar of Elroch

There is no "adjudication" in solving chess, there is a tablebase (with the usual hypothetical approach). Indeed, there are no games - rather a tree.

Avatar of efintushel

Right you are!

I had not considered the possibility of seeking or avoiding a draw by repetition. So the history of a game is, in fact, an element in assessing a position.