Is 79 maximal?

[Brunetti]

An UCI capable GUI should act as a referee and terminate the game. Same for mate, stalemate, 3-rep, etc.

Right, for mate, stalemate and insufficient material, but the referee can't intervene for the 50-move rule (and for repetitions), it's not a draw without an express request from a player. And apart from referees and GUIs, a position with a count greater than 100 is perfectly legal under the Laws of Chess, so a FEN should allow it.


Alex

[hgm]

That's some of the most idiotic xboard legacy...

An UCI capable GUI should act as a referee and terminate the game. Same for mate, stalemate, 3-rep, etc.

In other words, a UCI GUI should not support Chess according to FIDE rules. Just because it wants to use a deficient protocol for communicating with engines, it is better to change the rules of the game! After all, the main goal of GUIs is to implement a protocol, so it cannot be bothered by the rules of any game that would hinder that. Imagine that you would have to adapt the protocol so that it would be able to handle the full rules of the game. That would be truly unthinkable, the world upside down...

[Uri Blass]

* 3 for half move clock (cannot be 100 or it has to be mate)

Actually there's no limit on this counter: draw is not automatic and has to be claimed by a player (if he likes so), so a fully legal position may have values higher than 100. Just a detail, this doesn't alter your 96-byte allocation.


Alex

That's some of the most idiotic xboard legacy...

An UCI capable GUI should act as a referee and terminate the game. Same for mate, stalemate, 3-rep, etc.

The referee does not finish the game if no side claim a draw in 3-rep or 50 move rule without a claim of the players.

Here are the new fide rules(Note that 9.6 is new and based on the old rules it is possible that a game is never finished)

http://www.fide.com/fide/handbook.html? ... ew=article

9.2
The game is drawn, upon a correct claim by a player having the move, when the same position for at least the third time (not necessarily by a repetition of moves):
is about to appear, if he first writes his move, which cannot be changed, on his scoresheet and declares to the arbiter his intention to make this move, or
has just appeared, and the player claiming the draw has the move.
Positions areconsidered the same if and only if the same player has the move, pieces of the same kind and colour occupy the same squares and the possible moves of all the pieces of both players are the same. Thus positions are not the same if:
at the start of the sequence a pawn could have been captured en passant.
a king or rook had castling rights, but forfeited these after moving. The castling rights are lost only after the king or rook is moved.
9.3
The game is drawn, upon a correct claim by a player having the move, if:
he writes his move, which cannot be changed, on his scoresheet and declares to the arbiter his intention to make this move which will result in thelast50 moves by each player having been made without the movement of any pawn and without any capture, or
the last 50 moves by each playerhave been completed without the movement of any pawn and without any capture.

9.6
If one or both of the following occur(s) then the game is drawn:
the same position has appeared, as in 9.2b, for at least five consecutive alternate moves by each player.
any consecutive series of 75 moves have been completed by each player without the movement of any pawn and without any capture. If the last move resulted in checkmate, that shall take precedence.

[Brunetti]

9.6
If one or both of the following occur(s) then the game is drawn

Well, so now there's a limit of 150 and there's also the need to update the GUIs (and chess servers!) Anyway most engine tournaments are ran according to more restrictive limits (draw evaluation for x moves etc. so this shouldn't be an issue).

Alex

[zullil]

When you're programming a chess engine, or a chess GUI, it's better to be conservative:

Sure, good advice.

I wondered about the length of a FEN-string while coding a perft for my new (legal) move generator:

Code: Select all

louis@LZsT5610:~/Documents/Chess/Kirby$ ./perft 
FEN string = r1b1k2r/1n1n1q1p/1p1p1p1b/p1p1p1p1/P1P1P1P1/1P1P1P1P/Q1N1N1B1/R1B1K2R w KQkq a6
Depth = 6
Leaf nodes = 652550413
Time taken = 12382 ms

[bob]

When you're programming a chess engine, or a chess GUI, it's better to be conservative:

Sure, good advice.

I wondered about the length of a FEN-string while coding a perft for my new (legal) move generator:

Code: Select all

louis@LZsT5610:~/Documents/Chess/Kirby$ ./perft 
FEN string = r1b1k2r/1n1n1q1p/1p1p1p1b/p1p1p1p1/P1P1P1P1/1P1P1P1P/Q1N1N1B1/R1B1K2R w KQkq a6
Depth = 6
Leaf nodes = 652550413
Time taken = 12382 ms

There is NO defined limit. And when you factor in epd, which uses FEN, the lines get even longer. I would not assume a single space between fields, for example, as we have seen plenty over the years with two. I have also seen programs that produced half-move/move counters like this: 00005, rather than 5, as just one example.