Helpmate tablebases Every solution to every position, precomputed.

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KBBvkbn

6 pieces.

h#12
longest mate: h#9
deepest unique: 244
positions at that depth: h#9.5
deepest dual: h#7.5
deepest strict dual: 4,704,416,226
positions with a helpmate: 119,357,792
with a unique solution: 7,751,073,792
cells in the plane: 2,341,205,410 bytes
on disk

Deepest unique problems

h#9

8/8/1n6/3b4/8/8/2B5/KBk5 b - - 0 1

Kd2 Bd3 Kc3 Ba6 Kb4 Kb2 Ka5 Kc3 Nc8 Kd4 Kb6 Kxd5 Ka7 Kc6 Ka8 Kc7 Na7 Bb7#

pure self-block nocheck

h#9

8/8/6n1/8/3b1B2/8/8/BK5k b - - 0 1

Kg2 Kc2 Kf3 Kd3 Kxf4 Kxd4 Kg5 Kd5 Kh6 Bg7+ Kh7 Bh6 Kh8 Ke6 Nf8+ Kf7 Nh7 Bg7#

pure model ideal switchback self-block umnov

h#9

8/8/8/8/8/k7/4Bn2/1K1B3b b - - 0 1

Kb4 Bf1 Kc3 Bf3 Kd2 Bxh1 Ke1 Kc2 Nh3 Kd3 Kf2 Ke4 Kg1 Kf3 Kxh1 Kg3 Ng1 Bg2#

pure model ideal self-block kniest zajic nocheck

Deepest dual problems

Deepest dual with different first and last moves: h#7.5. The deepest dual overall is h#9.5, where the two solutions share a first or a last move.

Only one distinct idea exists at this depth: 5 positions share a solution.

h#7.5

7B/6b1/7n/8/8/8/1K1k4/6B1 w - - 0 1

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

Bd4 Kd3 Kc1 Ke4 Kd2 Kf5 Ke3 Kg6 Kf4 Kh7 Kg5 Kxh8 Kg6 Ng8 Bxg7#
Bxg7 Kd3 Bf8 Ke4 Kc3 Kf5 Kd4 Kg6 Ke5 Kh7 Kf6 Kh8 Kg6 Ng8 Bg7#

pure model ideal switchback self-block kniest nocheck

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