Helpmate tablebases Every solution to every position, precomputed.

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KRvkb

4 pieces.

h#7
longest mate: h#5
deepest unique: 365
positions at that depth: h#5
deepest dual: h#4.5
deepest strict dual: 2,826,157
positions with a helpmate: 129,146
with a unique solution: 1,892,352
cells in the plane: 1,567,916 bytes
on disk

Deepest unique problems

h#5

8/8/8/8/8/7k/6R1/K4b2 b - - 0 1

Bd3 Ra2 Kg3 Kb2 Kf2 Kc3+ Ke1 Kxd3 Kd1 Ra1#

pure model ideal mirror

h#5

8/8/8/8/8/8/6Rk/K1b5 b - - 0 1

Kh1 Rh2+ Kg1 Kb1 Kf1 Kc2 Ke1 Kd3 Kd1 Rh1#

single-piece single-piece:black nocapture umnov

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

h#5

8/8/8/5k2/6R1/8/8/1Kb5 b - - 0 1

Bg5 Kc2 Kg6 Kd3 Kh6 Ke4 Bf6 Kf5 Bg7 Rh4#

pure model ideal self-block nocapture nocheck

Deepest dual problems

Deepest dual with different first and last moves: h#4.5. The deepest dual overall is h#5, where the two solutions share a first or a last move.

h#4.5

8/8/8/8/7k/1b6/1R6/K7 w - - 0 1

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

Kb1 Kg3 Rxb3+ Kf2 Kc2 Ke1 Kd3 Kd1 Rb1#
Ra2 Kg3 Kb2 Kf2 Kc3+ Ke1 Kd3 Kd1 Ra1#

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

h#4.5

3k4/4R3/8/8/8/8/8/1K1b4 w - - 0 1

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

Re2 Kc7 Kb2 Kb6 Kc3 Ka5 Kc4 Ka4 Ra2#
Re8+ Kc7 Kb2 Kb6 Kc3 Ka5 Kc4 Ka4 Ra8#

pure model mirror single-piece single-piece:black nocapture

h#4.5

8/8/5k2/6R1/7b/8/8/2K5 w - - 0 1

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

Rg1 Bg5+ Kd1 Kg6 Ke2 Kh5 Kf3 Kh4 Rh1#
Rg2 Bg5+ Kd1 Kg6 Ke2 Kh5 Kf3 Kh4 Rh2#

pure model ideal self-block nocapture umnov