Not true
https://lichess.org/qTs81Cbo/
Look at this game...
@Garry_Springsteen said in #8:
> "218 is the maximum number of possible moves in a legal position" would have been a better title. As some people seem to be confused and think you're stating that every legal position can be reached in at most 218 moves.
Some positions are legal but not reachable though
Legal but not reachable...I'm not sure what you mean...If you can't reach a position from the starting position, it's not legal.
@Garry_Springsteen said in #73:
> Legal but not reachable...I'm not sure what you mean...If you can't reach a position from the starting position, it's not legal.
I think a good example is a chess 960 position where the bishop starts on a different square. There is nothing immediately wrong with it there are no situations where both kings are in check there are no triple checks or positions with 3 light square bishops and 8 pawns it is legal in that sense but you can't reach that position from the starting position because the bishops can't move unless the second rank pawns move but since pawns cannot go backwards you can't reach the particular 960 starting position.
Okay, but then you're using a "quick-check" definition of legality to discern it from reachability. The generally accepted definition is that a position is called legal if it can be reached by legal moves from the initial position.
@TW0_TIME_ACC said in #70:
> amazing - u conbined chess and maths
@UDITORIUM said in #71:
> Not true
> https://lichess.org/qTs81Cbo/
> Look at this game...
The claim is about the number of moves in a SINGLE POSITION not the number of moves of an ENTIRE GAME.
E.g. it's your turn and you have 218 moves to choose from :-)
@Richard_6B33 said in #72:
> > "218 is the maximum number of possible moves in a legal position" would have been a better title. As some people seem to be confused and think you're stating that every legal position can be reached in at most 218 moves.
>
> Some positions are legal but not reachable though
Actually, I don't remember for sure because it was a while ago, but as far as I do remember, all 218 move positions were reachable, because they were basically symmetrical copies of the same 12 positions and all 12 were reachable. So reachability wasn't actually the problem here. Legality is (e.g. not having your king in check). I guess this is the case, because shuffling around 9 queens is pretty easy and you can always shield away the black king in the corner, then take the last pieces at the right moment.
@Garry_Springsteen said in #73:
> Legal but not reachable...I'm not sure what you mean...If you can't reach a position from the starting position, it's not legal.
People have different definitions here. Personally, I favor the version of "legal" that does not require a position to be reachable from the starting position. Because imagine you set up some study in a chess tool and the tool screams "ILLEGAL POSITION". It does not match our intuitive sense of illegal. The rules of chess could well be used with a different starting position that then would make these "illegal" positions legal.
Having both terms nicely seperated, "legal" and "reachable", makes for more efficient and easier conversations.
If someone says "my position was illegal", you don't have to follow-up asking if that was, because it was reachable or because it violated the rules of chess.
Also, note that "reachable" implies "legal". So if you include "reachable" in "legal", you actually have both terms meaning the same thing, haha :D
And finally, checking reachability is, theoretically and for some very hard positions, a computationally difficult problem (universe dies before computer can figure it out), while "legal" is something very quick and easy to check. But if we include "reachable" into "legal", then it becomes hard to check.
Instead of fighting over the right definition of "legal position", just be clear which one you mean in discussions. I've seen soooo many debates where people fought over the right dictionary entry, instead of the actual subject, claiming that "their" definition should be adopted by the world as the one and only...
legal = legally reachable is a generally accepted definition. If you want to change the definition: good luck.
stats stats stats...
you are my type bro