Author: Steven Edwards
Date: 21:16:06 09/09/03
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On September 09, 2003 at 23:51:32, Jon Dart wrote: >On September 09, 2003 at 18:33:22, Steven Edwards wrote: >Even in normal chess, if you take into account the previous history of the game, >there are six possible castling statuses. Arasan names these as follows: > > CanCastleEitherSide, > CanCastleKSide, > CanCastleQSide, > CastledKSide, > CastledQSide, > CantCastleEitherSide > >FEN can't currently distinguish these: it can only indicate whether or not >castling is possible, not whether or not it has occurred. Obviously, if a side has already castled, it cannot castle again. So any deficiency here is the lack of reporting that a castling has occurred in the game history. I think that this is more of a history issue than a position status issue as it has no effect on any move generation or analysis. Note that EPD has the "hv" (history variation) opcode that can be used to supply the entire previous move history. It's kind of like "sv" (supplied variation; compare with "pv") but from the start of the game instead of from the current position. >>4. The centipawn evaluation operand type needs a mate score indication >>correction. The old "ce" has special scores to indicate mate-in-N and lose-in-N evaluations. That's not too bad, but unfortunately the special values used are broken and represent an unwanted revealing of the internals of the analyzing program. Example: "ce 32766" is a mate in 1 and "ce 32764" is a mate in 2 but "ce 32765" is undefined and is, in fact, an error. This can be fixed, and the SPCT has such a fix already, but using the fix will likely break any software using the old score interpretation. That would be ungood. So I think that it's time to deprecate "ce" and let it fade into disuse by being supplanted with a correct and new decimal pawn unit evaluation opcode and, probably, a new opcode for representing special evaluations. This would handle forced mates, forced losses, and also identify forced draws by kind (e.g., stalemate, three time occurrance).
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