# [Retros] How many times could a Diagram be repeated during a proofgame?

andrew buchanan andrew at anselan.com
Sun Feb 8 19:25:00 EST 2009

Hi Jonathan,

This is a reply to an old mail of yours. I found it in my draft Folder.

> As I understand it, we're defining a position as "different" if different

> moves are available to each side...

(1) We don't get to define what is a position. That is defined for us in the Laws in the section 9.something on Draw by Repetition of Position.

> ...even though logically in a game

> having the extra option to castle shouldn't prevent one side from

> claiming a draw if it wants to.

(2) I like your idea that if the current position dominates a previous position, then it should be treated equivalently for Repetition purposes.

So for example, if a position occurs 3 times (White to Play) with WKa1, except the first time there was also BQb1 present on the board, then does White have the moral right to claim a draw? After all, he now has all the moves and more that were at his disposal the first time round.

But your example (if I've understood your words right) had the domination the wrong way round: White can only lose castling rights not gain them, and its less convincing an argument for a draw if White has less moves available than the first time the diagram occurred. Surely Black could claim that he is making slow but steady progress by whittling away White's castling rights. (Indeed there is a famous problem by somebody where White spends the first 4 double moves eliminating Black's castling rights, returning twice to the original diagram.)

Of course if only White has lost castling rights, then Black may be considered to have the right to claim a draw. (Ignoring the mechanical arguments one sometimes gets about whether Black has to write his last move and not actually make it, yawn. By "mechanical", I mean "characteristic of the Laws pertaining to the mechanics of playing the physical game", e.g. touch move, clock management, recording the moves, disqualification for cheating, etc.)

> Yet, unless I've missed something, we are defining two positions as

> the same even if one is winning but the second is not because of

> the 50 moves rule!

>

> We could argue that a position with 50 moves left is different from

> one with 47 moves left is different from one with 2 moves left...

(3) The notion of "position" *only* exists in the Laws to define draw by repetition thereof. I suggest that you might use the word "game" instead. Two *games* do map on to the same position even if one game is winning but the second is not because of the 50 moves rule.

> Or does this way lie madness?

(4) Madness lies all about on this crazy planet where I seem to find myself. But I think here we just have a definitional question.

Cheers,
Andy

--- A J Mestel <A.J.Mestel at damtp.cam.ac.uk> wrote:

> As I understand it, we're defining a position as "different" if different

> moves are available to each side, even though logically in a game

> having the extra option to castle shouldn't prevent one side from

> claiming a draw if it wants to.

>

> Yet, unless I've missed something, we are defining two positions as

> the same even if one is winning but the second is not because of

> the 50 moves rule!

>

> We could argue that a position with 50 moves left is different from

> one with 47 moves left is different from one with 2 moves left...

>

> Or does this way lie madness?

>

> Jonathan

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