Helpmate tablebases Every solution to every position, precomputed.

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KPvkn

4 pieces.

h#8.5
longest mate: h#7.5
deepest unique: 8
positions at that depth: h#7.5
deepest dual: h#6
deepest strict dual: 9,685,606
positions with a helpmate: 91,156
with a unique solution: 5,548,032
cells in the plane: 4,720,178 bytes
on disk

Deepest unique problems

h#7.5

K7/8/8/n7/2P5/8/8/7k w - - 0 1

c5 Kg2 c6 Kf3 c7 Ke4 c8=Q Kd5 Qf5+ Kc6 Kb8 Kb6 Kc8 Ka7 Qxa5#

pure model ideal mirror promotion single-piece single-piece:black

h#7.5

K7/8/2n5/8/8/8/2P4k/8 w - - 0 1

c3 Nd4 cxd4 Kg3 d5 Kf4 d6 Ke5 d7 Kd6 Ka7 Kc7 Ka6 Kb8 d8=Q#

pure model ideal mirror promotion excelsior excelsior:white nocheck umnov

h#7.5

1K6/8/8/8/2n5/2P5/7k/8 w - - 0 1

Ka8 Nd6 c4 Kg3 c5 Kf4 cxd6 Ke5 d7 Kd6 Ka7 Kc7 Ka6 Kb8 d8=Q#

set-play pure model ideal mirror promotion nocheck umnov

Deepest dual problems

Deepest dual with different first and last moves: h#6. The deepest dual overall is h#7.5, where the two solutions share a first or a last move.

h#6

8/8/6k1/8/8/K5P1/6n1/8 b - - 0 1

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

Kf5 g4+ Ke4 g5 Kd3 g6 Kc2 g7 Kb1 g8=Q Ka1 Qa2#
Nh4 gxh4 Kf5 h5 Ke4 h6 Kd3 h7 Kc2 h8=Q Kb1 Qb2#

promotion single-piece single-piece:white single-piece:black

h#6

8/7n/8/3K4/8/5P1k/8/8 b - - 0 1

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

Kh4 Kc6 Kg5 f4+ Kf6 f5 Ke7 f6+ Kd8 f7 Ng5 f8=Q#
Ng5 f4 Kg4 fxg5 Kf5 g6 Kf6 g7 Kf7 Kd6 Ke8 g8=Q#

pure model ideal mirror promotion umnov

h#6

8/2K5/8/8/8/8/1n2P3/5k2 b - - 0 1

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

Nd1 e4 Ke2 e5 Kd3 e6 Kc4 e7 Kb5 e8=Q+ Ka6 Qa4#
Na4 e4 Ke2 e5 Kd3 e6 Kc4 e7 Kb5 e8=Q+ Ka6 Qxa4#

pure model ideal mirror promotion excelsior excelsior:white single-piece single-piece:white umnov