Max moves in a position

[MahmoudUthman]

Is it even possible for such a position to be encountered while searching ?
and what about the maximum number of captures and quiets separately ?

[bob]

Is it even possible for such a position to be encountered while searching ?
and what about the maximum number of captures and quiets separately ?

Easiest solution I know of is what I use. A Large array to store the moves, and an pointer per ply that points to the last move generated for this ply + 1 (obviously the pointer for ply - 1 points to the first move for this ply. Now a position with 1000 legal moves would not cause a problem, all I have to worry about is the max size of that array, and since the end is never used in normal positions, you can make it large enough that you feel completely confident it won't be compromised.

One serious advantage is no "gaps" between plies. The array is filled in from position 0 through the max with no unused values between each ply, which makes it about as cache-friendly as can be done.

[Ras]

while 218 is the discovered maximum, I ran many test games, and the maximum in real games were 93 (pseudo-legal) moves. My movelist arrays have 150 moves, which is sufficient for real applications.

However, if you aren't as low on RAM as I am (28k stack), you can safely allocate something like 256 moves per position.

[D Sceviour]

Hi All,

Does anyone know the maximum possible moves in a position (any position).
I am working on my move gen and want to allow enough spots in the array, but not too many.

Thanks
Laurie.

Try this:
[d]R6R/3Q4/1Q4Q1/4Q3/2Q4Q/Q4Q2/pp1Q4/kBNN1KB1 w - - 0 1

from:
http://www.chess.com/forum/view/general ... s-possible

[Fulvio]

The array is filled in from position 0 through the max with no unused values between each ply, which makes it about as cache-friendly as can be done.

This is an interesting talk about "Hybrid Data Structures" used by LLVM:
https://www.youtube.com/watch?v=vElZc6zSIXM

The idea is to allocate a small vector on the stack that can automatically grow into the heap; he said that in LLVM it improves speed.

[sasachess]

I add my question: what is the maximum number of capture moves?

[AlvaroBegue]

I add my question: what is the maximum number of capture moves?

Rooks and bishops can capture at most 4 things, and every other piece can capture at most 8 things, so 4*4 + 12*8 = 112 is an upper bound.

[MahmoudUthman]

I add my question: what is the maximum number of capture moves?

Rooks and bishops can capture at most 4 things, and every other piece can capture at most 8 things, so 4*4 + 12*8 = 112 is an upper bound.

I think that in the configuration (2R,2B,9Q,2N,1K) that you used a king can only have a maximum of 3 captures (1R , 1B ,1N , Touching it without defending each other).

[AlvaroBegue]

I add my question: what is the maximum number of capture moves?

Rooks and bishops can capture at most 4 things, and every other piece can capture at most 8 things, so 4*4 + 12*8 = 112 is an upper bound.

I think that in the configuration (2R,2B,9Q,2N,1K) that you used a king can only have a maximum of 3 captures (1R , 1B ,1N , Touching it without defending each other).

I see what you mean, but I don't think it's quite right. The opponent could have a different material configuration, and then the king can capture at least five things (five pawns).

[MahmoudUthman]

I add my question: what is the maximum number of capture moves?

Rooks and bishops can capture at most 4 things, and every other piece can capture at most 8 things, so 4*4 + 12*8 = 112 is an upper bound.

I think that in the configuration (2R,2B,9Q,2N,1K) that you used a king can only have a maximum of 3 captures (1R , 1B ,1N , Touching it without defending each other).

I see what you mean, but I don't think it's quite right. The opponent could have a different material configuration, and then the king can capture at least five things (five pawns).

yes , I forgot about pawns of the other side but how can you get 5 pawns touching the king without at least defending one of their own ? plus if you add any other piece it will defend more pawns so 4 pawns seems to be the maximum , right ?