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No reachable chess position with more than 218 moves

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Re: No reachable chess position with more than 218 moves

#131

Post by Certhas »

CrazyStat wrote: post #70
unkulunkulu wrote: post #63

Earlier quoted context omitted.

there certainly is if you consider 50 moves rule. And you can derive an easy upper bound from that as 50x8x8x2 (basically each 50 moves you make a pawn move) if you only consider 3 moves repetition and not 50 move rule then this is harder and the number becomes one of those crazy combinatorical numbers.

> And you can derive an easy upper bound from that as 50x8x8x2 (basically each 50 moves you make a pawn move) This is not high enough, because the 50 move rule also resets when a piece is captured.

Actually no. 50×(16×6 + 32) = 50×(16× 8) works I think. Every 50 moves, move a pawn or capture. There are 16 pawns. Each pawn can be moved 6 times, so there are 16×6 pawn moves available. In addition there are 32 captures available.

Re: No reachable chess position with more than 218 moves

#132

Post by fwip »

ojo-rojo wrote: post #95
leoff wrote: post #75

Earlier quoted context omitted.

I seriously thought they meant "it's not possible to have a chess game with more than 218 moves"

Yeah, I'm still confused.

There is no reachable[1] chess position[2] at which a player has more than 218 valid moves[3] to choose from.

[1] Able to happen while following the rules of chess

[2] The arrangement of chess pieces on the board

[3] A valid move is the motion of one piece to a place on the board, which doesn't break the rules of chess - e.g: "King to E4."

Re: No reachable chess position with more than 218 moves

#133

Post by KingLancelot »

refulgentis wrote: post #130
kelipso wrote: post #84

Earlier quoted context omitted.

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

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.

[dead]

Re: No reachable chess position with more than 218 moves

#134

Post by pxx »

sim7c00 wrote: post #72
dmurray wrote: post #64

Earlier quoted context omitted.

I believe 8848.5 under modern rules (with the 75-move rule, as in FIDE rules since 2014). There's a reasonably rigorous demonstration here: https://wismuth.com/chess/longest-game.html

how can the longest game have half a move???

An A press is an A press. You can't say it's only a half.

Re: No reachable chess position with more than 218 moves

#136

Post by absoflutely »

sverhagen wrote: post #37
WithinReason wrote: post #15

Earlier quoted context omitted.

Thanks, I misunderstood the entire article. Great writing!

How can those two things be true at the same time? Unless you appreciate misunderstanding what you read...?

You hit the nail on the head. They aren't both true which is why the second sentence is sarcasm.

Re: No reachable chess position with more than 218 moves

#137

Post by AceyMan »

stavros wrote: post #59
codeulike wrote: post #10

They dont really spell it out but they mean "from this position the player has 218 possible legal moves to choose from"

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.

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

Re: No reachable chess position with more than 218 moves

#138

Post by OwlGoesHoot »

stavros wrote: post #87
kelipso wrote: post #84

Earlier quoted context omitted.

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

Re: No reachable chess position with more than 218 moves

#139

Post by tromp »

stavros wrote: post #59
codeulike wrote: post #10

They dont really spell it out but they mean "from this position the player has 218 possible legal moves to choose from"

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.

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.
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