Helpmate tablebases Every solution to every position, precomputed.

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KQBvkb

5 pieces.

h#10
longest mate
h#7
deepest unique
4
positions at that depth
h#7
deepest dual
h#4
deepest strict dual
147,182,760
positions with a helpmate
18,190,470
with a unique solution
121,110,528
cells in the plane
111,296,193 bytes
on disk

Deepest unique problems

h#7

8/8/6b1/8/8/6Qk/3B4/K7 b - - 0 1

  1. Kxg3 Kb2 Kg4 Kc3 Kf5 Kd4 Kf6 Bc3 Kg7 Ke5 Kh8 Kf6 Bh7 Kf7#

self-block nocheck

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

h#7

8/8/8/5bB1/8/6Qk/8/K7 b - - 0 1

  1. Kxg3 Kb2 Kg4 Kc3 Kh5 Kd4 Kg6 Ke5 Kh7 Kf6 Kh8 Kf7 Bh7 Bf6#

self-block nocheck

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

h#7

8/8/6b1/8/6k1/7Q/3B4/K7 b - - 0 1

  1. Kxh3 Kb2 Kg4 Kc3 Kf5 Kd4 Kf6 Bc3 Kg7 Ke5 Kh8 Kf6 Bh7 Kf7#

switchback self-block nocheck

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

Deepest dual problems

Deepest dual with different first and last moves: h#4. The deepest dual overall is h#7, where the two solutions share a first or a last move.

Only 2 distinct ideas exist at this depth.

h#4

8/8/8/8/3K4/8/5Q2/1B3kb1 b - - 0 1

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

  1. Kxf2 Kd3 Kg2 Ke2 Kh1 Kf1 Bh2 Be4#
  2. Bxf2+ Ke4 Kg1 Kf3 Kh1 Be4 Bg1 Kg3#

switchback self-block

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

h#4

8/5b1k/6Q1/4B3/3K4/8/8/8 b - - 0 1

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

  1. Kxg6 Ke4 Kh7 Kf5 Bg8 Kf6 Kh8 Kg6#
  2. Bxg6 Kd5 Kg8 Ke6 Bh7 Kf6 Kh8 Kf7#

switchback self-block single-piece single-piece:white nocheck

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