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Comment by stavros | Hacker News Reader

Ah, wow, I read the article wrong all this time, thank you. I thought they meant "the maximum number of moves you can make to reach any chess position is 218", and I was wondering why the article made no sense to me.

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It's conceivable that the maximum number of plies (half-moves) you need is 218. The best known lower bound on needed number of plies is 185 for "Harry Goldsteen's furthest position" https://timkr.home.xs4all.nl/chess2/diary.htm So perhaps the hardest-to-reach position manages to improve on that by an additional 33 plies.

The word 'available' inserted at the right spot would make all the difference in clarity here.

imo "possible" would be better

I'd go with "legal," which also implies possible.

I thought the same, but no doubt pawn promotion rules dramatically increase the depth needed to reach certain positions.

Is that weird? I feel like it’s plausible though. Very rare to have chess games with more than 200 moves.

Yeah I kind of thought that it meant "you can get to any valid position in 218 moves max", it was hard to parse.

I read it as “there is no legal position for which the minimum number of moves necessary to reach it is greater than 218” but I also did not read the whole article before coming to check the comments

It’s also rare to have one with more than 50 moves. I’m curious if this class of observation will help establish a true bounds. Especially because we don’t have a definition of what it means - my instinct is to first do that, so “infinity” isn’t the obvious upper bound.

Proving this feels more difficult than proving what’s in the OP article, because here you have to show path lengths between original position and all possible positions have a max length, while OP article had to show all positions have a max degree. Path length just seems like a harder problem compared to node degree.

What? Lots of serious chess games last more than 50 moves

Not sure if I'm reading your comment correctly

The upper bound of moves is 8848.5 https://www.reddit.com/r/chess/comments/168qmk6/longest_poss...

... under the rule that after 75 moves without a capture or pawn advancement the game is drawn

You read a comment saying it’s rare to have more than 200 moves, then a reply noting more than 50 is also rare, then suggested you were confused and maybe it was unreadable and asked “What?” because…some games have above 50 moves. shrugs

Thanks for note re: upper bound with 75 moves without pawn advancing constraint.

More than 50 moves in a game is hardly rare, hence my surprised reaction

The upper bound is a few thousand. A game is considered drawn if no pawn has moved and no piece has been captured for 50 moves. And there's also the threefold repetition rule: if the same exact position (counting things like castling eligibility etc) occurs three times it's drawn.

I think the upper bound is 6300, then. Each pawn can move 6 times, times 16 pawns, times 50 moves before a game ending draw, plus each capturable piece that can delay the game another 50 moves (15 on each side)

lol same here.

This is not so interesting then…

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