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How long can a chess game theoretically last in terms of moves with respect to the rules of draw?

AbhaySankar12

^^

Rook_Handler

0

Alramech
AbhaySankar12 wrote:

How long can a chess game theoretically last in terms of moves with respect to the rules of draw?

Check out this blog post: https://www.chess.com/blog/BradenLaughlin/what-is-the-longest-possible-game-of-chess

llama47

The full answer is pretty involved, and takes some thinking / work.

I'll give the outline of the answer and leave it to the reader to fill in the details.

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The 50 move rule (sometimes the 75 move rule) is reset by captures or pawn moves.
30 captures can be made.
96 pawn moves can be made.
However pawns capture and move forwards at the same time, so they are duplicates, but with a little thinking we can minimize the duplicates to 8.

So for a draw in X (usually X is 50 i.e. the 50 move rule) we'll have 118 sets of X.

However white can't make all the captures right? So there is -1 half move (also called -1 ply) every time we switch from white doing the pawn moves or captures to black (or vice versa).

With a clever trick, you only need to switch 3 times.

So the answer to the title (in half-moves also called ply) is to multiply 118 by 2X and then subtract 3 -- where X is the highest number of moves without a capture or pawn move allowed.

For the 50 move rule the answer is 11797 ply or 5898.5 moves.

llama47
Alramech wrote:
AbhaySankar12 wrote:
How long can a chess game theoretically last in terms of moves with respect to the rules of draw?

Check out this blog post: https://www.chess.com/blog/BradenLaughlin/what-is-the-longest-possible-game-of-chess

A lot of places on the internet give the wrong answer because they switch 4 times instead of using the trick to do 3.

So they give the answer found in the link above... which is wrong.