Helpmate tablebases Every solution to every position, precomputed.

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KRvkr

4 pieces.

h#7
longest mate: h#5.5
deepest unique: 9
positions at that depth: h#6
deepest dual: h#5
deepest strict dual: 2,694,256
positions with a helpmate: 114,213
with a unique solution: 1,892,352
cells in the plane: 1,206,853 bytes
on disk

Deepest unique problems

h#5.5

8/8/5k2/8/6R1/8/7r/K7 w - - 0 1

Kb1 Rh6 Kc2 Rg6 Kd3 Kg7 Ke4 Kh6 Kf5 Rg7 Rh4#

pure model ideal self-block nocapture nocheck

h#5.5

8/3R4/6k1/8/1r6/8/8/K7 w - - 0 1

Ka2 Rf4 Kb3 Rf7 Kc4 Kg7 Kd5 Kf8 Ke6 Rg7 Rd8#

pure model ideal self-block nocapture nocheck

h#5.5

5k2/7R/8/8/8/8/6r1/1K6 w - - 0 1

Kc1 Rg7 Kd2 Kf7 Ke3 Kg6 Rxg7+ Kh5 Kf4 Kh4 Rh7#

pure model ideal mirror switchback

Deepest dual problems

Deepest dual with different first and last moves: h#5. The deepest dual overall is h#6, where the two solutions share a first or a last move.

Only one distinct idea exists at this depth: 2 positions share a solution.

h#5

3r4/5k2/7R/8/8/8/8/2K5 b - - 0 1

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

Rd6 Rh8 Rh6 Kd2 Kg6 Ke3 Kh5 Kf4 Kh4 Rxh6#
Rh8 Rh1 Kg6 Kd2 Rh2+ Ke3 Kh5 Kf4 Kh4 Rxh2#

pure model ideal mirror switchback umnov