Helpmate tablebases Every solution to every position, precomputed.

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KBBvknn

6 pieces.

h#13
longest mate: h#8.5
deepest unique: 17
positions at that depth: h#9
deepest dual: h#7
deepest strict dual: 2,413,135,491
positions with a helpmate: 42,943,742
with a unique solution: 7,751,073,792
cells in the plane: 1,300,053,404 bytes
on disk

Deepest unique problems

h#8.5

n7/8/5B2/8/7B/7k/2n5/1K6 w - - 0 1

Bg3 Ne3 Bb8 Ng4 Kc2 Nc7 Kd3 Kg3 Be5+ Kh4 Ke4 Ne6 Kf5 Ng5 Kg6 Nh3 Bg3#

pure model ideal self-block nocapture

h#8.5

B7/8/8/7n/8/3B3n/8/k1K5 w - - 0 1

Kd2 Kb2 Ke3 Kc1 Bf1 Kd1 Bf3+ Ke1 Ke4 Kf2 Bxh5 Kg1 Kf3 Kh1 Kg3 Ng1 Bg2#

pure self-block

h#8.5

8/7k/8/1B5B/1n6/8/8/1n1K4 w - - 0 1

Kc1 Kg7 Kb2 Kf6 Kb3 Ke5 Ka4 Kd4 Ka5 Kc3 Kb6 Kb3 Bc4+ Ka4 Bhf7 Na3 Bb3#

pure model ideal self-block nocapture

Deepest dual problems

Deepest dual with different first and last moves: h#7. The deepest dual overall is h#9, where the two solutions share a first or a last move.

h#7

n7/8/8/1B6/8/2k5/5n2/1K5B b - - 0 1

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

Kd2 Bf1 Ke1 Kc2 Nh3 Kd3 Kf2 Ke4 Kg1 Kf3 Kxh1 Kg3 Ng1 Bg2#
Nb6 Kc1 Nd3+ Kd1 Nc1 Ke1 Kc2 Kf2 Kd1 Bd3 Nc4 Bhe4 Nd2 Bc2#

pure model ideal self-block kniest umnov

h#7

8/8/5B2/4k3/2n1n3/6B1/8/1K6 b - - 0 1

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

Kd5 Bg5 Kd4 Kc1 Kc3 Kd1 Kb2 Bc1+ Ka1 Kc2 Na3+ Kb3 Nb1 Bb2#
Kf5 Kc2 Kg6 Kd3 Ne5+ Ke3 Kh6 Kf4 Ng6+ Kg4 Ng5 Bge5 Nh7 Bg7#

pure model ideal self-block nocapture

Note: the diagram has no legal last move, so it cannot arise in a game.

h#7

8/2B5/3k3B/8/3n4/7n/8/1K6 b - - 0 1

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

Ke6 Bhf4 Nf3 Kc2 Kf5 Kd3 Kg4 Ke4 Kh4 Kf5 Nh2 Kg6 Ng4 Bg3#
Ke7 Kb2 Ne6 Kc3 Nf8 Kd4 Kf7 Ke5 Kg8 Kf6 Kh8 Kf7 Nh7 Bg7#

pure model ideal self-block nocapture nocheck

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