Fen is incomplete

[Henk]

Fen is incomplete for it does not contain information about whether three fold repetition would occur for the next moves to be played.

Looks like you have to store position plus part of the move history of the game the position was taken from.

[hgm]

Indeed, a FEN is for encoding board position, not for game history. It only contains the part of the game state relevant for deciding about move legality.

[Henk]

I don't know if that will give a problem when doing MCTS. Now I clear the move history when searching the position for then it will comply if I store the game from the given start position (fen).

If I don't clear the move history then I search/simulate and store games where for instance only one move had been played because of three fold repetition draw.

[kliles]

FEN also does not encode other information along the same lines: whether either of the Kings has moved (and moved back for example...) and the same for Rooks (with respect to the legality of castling etc).

[zullil]

FEN also does not encode other information along the same lines: whether either of the Kings has moved (and moved back for example...) and the same for Rooks (with respect to the legality of castling etc).

But it does explicitly indicate castling availability.

[bob]

FEN also does not encode other information along the same lines: whether either of the Kings has moved (and moved back for example...) and the same for Rooks (with respect to the legality of castling etc).

Eh? FEN has ALWAYS included castling status for both directions, both sides. The KQkq you often see means that white can castle both directions (KQ) and same for black (kq). If the king moves, those are not shown for that side. If either rook moves, the corresponding K or Q is removed...

[kliles]

Thanks for the rebuttal! I appreciate the correction.