Knox update Dots and Boxes

1 replies. Last post: 2004-07-29

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Knox update
  • Knox (Computer) at 2004-07-29

    All the Nimstring stuff is finished.

    I believe this would have a bigger effect on a 7x7 or 8x8

    than on the 6x6. About the only difference in play on

    the 6x6 is that when the board quickly divides up into

    two or three pieces, Knox will be able to make reasonably

    good moves immediately rather than drifting for a few moves.

    Also, three errors/problems were fixed.

    1. Near the end of game 198465 vs. yper, a programming error caused Knox to misevaluate the result of taking a

    long chain which caused Knox to incorrectly give away the last two boxes of the chain. This reduced Knox's margin of victory from 15-10 to 13-12.

    1. In the endgame of game 189320 vs. Taral, Knox's best

    move was a pre-emptive sacrifice of a chain of 6-boxes –

    the longest chain on the board! Knox missed it because the

    move generator never entered the move into the search.

    There are several situations where you can ignore certain

    moves without risking an avoidable loss. For example,

    never play in an independent chain if a shorter independent

    chain is available. Knox will avoid searching moves like this in order to potentially allow a deeper search.

    The criteria for considering a pre-emptive sacrifice neglected to take into account the current score at the current point in the search. This wasn't a programming

    error but rather something I didn't think through

    adequately enough when I wrote that piece of code. (In the game, this oversight reduced the winning margin from 15-10 to 14-11).

    1. At the end of game 190919 vs. Bonnie McGowan, the

    remaining position consisted of a 6-chain attached to

    a 12-loop. Bonnie opened up the 12 loop. When I entered the move into Knox, it immediately printed out a list of

    its moves, printed out the final filled-in board, and announced the final score. So I went ahead and filled

    in everything on littlegolem but when I later looked at the move list I noticed that it wasnot legal! After Bonnie's move, you can form one long takeable path from her move to the “join” box and after that, there will be one very long takeable path that includes the rest of

    the loop plus the outside chain. Knox took that second

    path first! I.e. it took the path up to the join box,

    played a move on the other side of join box, and then as

    if this completed the square, continued taking the outside

    chain and only then did it take the first path from

    Bonnie's move to the join box. Playing the moves in this

    order is equivalent to taking two turns in a row! Having

    to resign this particular game due to a programming error would have been especially painful because Knox managed to get a rare 25 to 0 shutout victory!

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