Helpmate tablebases Every solution to every position, precomputed.

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KBvkrbb

6 pieces.

h#9.5
longest mate
h#8.5
deepest unique
2
positions at that depth
h#8.5
deepest dual
h#7
deepest strict dual
3,379,181,680
positions with a helpmate
44,278,151
with a unique solution
7,751,073,792
cells in the plane
2,619,513,707 bytes
on disk

Deepest unique problems

Only 2 distinct ideas exist at this depth.

h#8.5

b7/8/8/8/8/8/2B2b2/k1Kr4 w - - 0 1

  1. Kxd1 Kb2 Be4 Kc3 Bxa8 Kd3 Kc1 Ke2 Kc2 Kf1 Kd3 Kg1 Ke4 Kh1 Kf3 Bg1 Kg3#

switchback self-block nocheck

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

h#8.5

b7/8/8/8/8/3r4/4Bb2/1k1K4 w - - 0 1

  1. Bxd3+ Kb2 Be4 Kc3 Bxa8 Kd3 Kc1 Ke2 Kc2 Kf1 Kd3 Kg1 Ke4 Kh1 Kf3 Bg1 Kg3#

self-block

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#7. The deepest dual overall is h#8.5, where the two solutions share a first or a last move.

Only 2 distinct ideas exist at this depth.

h#7

7k/8/2b5/8/8/2rB4/8/K5b1 b - - 0 1

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

  1. Kg7 Bc4 Rh3 Kb2 Be3 Kc3 Bh6+ Kd4 Kg6 Ke5 Kh5 Kf5 Rh4 Bf7#
  2. Bd5 Kb2 Rc8 Bc4 Be3 Kc3 Bh6 Kd4 Kh7 Ke5 Rh8 Kf6 Bg8 Bd3#

switchback self-block nocapture

h#7

7k/7B/8/5b2/8/8/2r5/K3b3 b - - 0 1

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

  1. Rh2 Bg8 Bd2 Kb2 Bh6+ Kc3 Kg7 Kd4 Kg6 Ke5 Kh5 Kxf5 Rh4 Bf7#
  2. Rc8 Kb2 Be6 Bb1 Bc3+ Kc2 Kh7 Kd3 Rh8 Ke4 Bg8 Kf5 Bg7 Kg5#

self-block