Helpmate tablebases Every solution to every position, precomputed.

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KBBvkn

5 pieces.

h#12
longest mate: h#9
deepest unique: 2
positions at that depth: h#9
deepest dual: h#5
deepest strict dual: 85,412,192
positions with a helpmate: 1,685,106
with a unique solution: 121,110,528
cells in the plane: 34,866,129 bytes
on disk

Deepest unique problems

Only 2 distinct ideas exist at this depth.

h#9

8/8/4n3/8/3B4/8/1B4k1/3K4 b - - 0 1

Kf3 Bc1 Ke4 Ke2 Kxd4 Kf3 Ke5 Kg4 Kf6 Kh5 Kg7 Bh6+ Kh8 Kg6 Nf8+ Kf7 Nh7 Bg7#

pure model ideal self-block

h#9

8/8/4n3/8/3B4/2B5/6k1/3K4 b - - 0 1

Kf3 Bd2 Ke4 Ke2 Kxd4 Kf3 Ke5 Kg4 Kf6 Kh5 Kg7 Bh6+ Kh8 Kg6 Nf8+ Kf7 Nh7 Bg7#

pure model ideal self-block

Deepest dual problems

Deepest dual with different first and last moves: h#5. The deepest dual overall is h#9, where the two solutions share a first or a last move.

h#5

7n/6k1/8/8/8/8/2BB4/2K5 b - - 0 1

Two solutions, with different first and last moves (2 starts, 2 ends).

Ng6 Kd1 Nf4 Ke1 Kh6 Kf2 Kh5 Kg3 Ng6 Bd1#
Nf7 Kd1 Nd6 Ke2 Ne8 Ke3 Kh6 Kf4 Ng7 Kg4#

switchback self-block single-piece single-piece:white nocapture nocheck

h#5

8/7k/8/5B2/8/8/8/2K2nB1 b - - 0 1

Two solutions, with different first and last moves (2 starts, 2 ends).

Kh6 Bg4 Nh2 Kd2 Kg5 Ke3 Kh4 Kf4 Nf3 Bf2#
Kg7 Kd1 Kh6 Ke2 Ng3+ Kf3 Nh5 Kg4 Ng7 Be3#

self-block nocapture

Note: the side to move is in check in the diagram.

h#5

6k1/8/7B/8/8/8/6n1/1B1K4 b - - 0 1

Two solutions, with different first and last moves (2 starts, 2 ends).

Kf7 Bf4 Kf6 Bg3 Kg5 Ke2 Kg4 Kf2 Kh3 Bf5#
Nh4 Bc1 Kg7 Kd2 Kh6 Ke3 Nf5+ Kf4 Ng7 Kg4#

self-block single-piece single-piece:black nocapture