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It uses the FEN, which is the standard notation for chess positions. And it's the right choice, IMO -- if two positions are the same they should have the same

• deleted 2y ago
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• vikingerik 2y ago
  The move order matters, for detecting threefold or fivefold repetition, or the 50 move draw limit. To adhere to that properly, you need to somehow represent all previous positions that could be reached again, and the number of times it has occurred. Of course you can get that by including all the move history, but it's also possible to prune it a lot, like any capture or pawn move can flush the history since no previous position is reachable. But it's still a bit more complicated than just representing the current position. FEN doesn't account for this, deliberately leaving the history out of scope. It's a matter of preference whether you'd want a tool like this to handle those cases.
• ummonk 2y ago
  No it shouldn’t. Move history has to be encoded so draw by threefold / fivefold repetition and fifty moves / seventy five moves can be claimed / detected.
  • Sesse__ 2y ago
    The half-move counter in the FEN takes care of the 50/75 move rule. You do need the history if you want to implement the threefold/fivefold repetition rule, but it's rare that it is actually relevant for e.g. a chess engine's strength.