Helpmate tablebases Every solution to every position, precomputed.

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KQBNvk

5 pieces.

h#8
longest mate
h#6
deepest unique
98
positions at that depth
h#7
deepest dual
h#3
deepest strict dual
155,613,282
positions with a helpmate
26,395,571
with a unique solution
121,110,528
cells in the plane
112,007,612 bytes
on disk

Deepest unique problems

h#6

8/6N1/8/8/8/2B5/8/K1kQ4 b - - 0 1

  1. Kxd1 Ka2 Kc1 Kb3 Kb1 Kc4 Ka2 Ne6 Ka3 Bb4+ Ka4 Nc5#

switchback single-piece single-piece:black

Note: the side to move is in check in the diagram; the solution begins with a capture.

h#6

8/6N1/8/8/Q7/k7/1B6/1K6 b - - 0 1

  1. Kxa4 Bc3 Ka3 Kc2 Ka2 Kd3 Kb1 Nf5 Kc1 Bd2+ Kd1 Ne3#

switchback single-piece single-piece:black

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

Deepest dual problems

Deepest dual with different first and last moves: h#3. The deepest dual overall is h#7, where the two solutions share a first or a last move.

h#3

8/8/8/4B3/4Nk2/7Q/8/K7 b - - 0 1

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

  1. Kxe4 Qf1 Ke3 Kb2 Kd2 Bf4#
  2. Kxe5 Kb2 Kd5 Nf6+ Kd4 Qc3#

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

Note: the side to move is in check in the diagram; the solution begins with a capture.