A tablebase for a cooperative game
A helpmate is a chess problem in which Black moves first and
both sides cooperate to checkmate Black as quickly as possible. h#3
means mate after three moves by each side. A helpmate is only a sound problem
when it has exactly one solution; a second one is a dual.
Because both sides want the same thing, the value of a position is a plain shortest path, and a whole material class can be solved at once. For every legal position in a class these tables store the distance to mate and the number of distinct optimal solutions. The second number is the one that tells a composer whether a position is a problem.
What is here: the deepest sound problem in every material class, 930 puzzles with a unique solution you can solve on the board, and the corpus, table by table.
The deepest sound problem in every material class
One position per class: the longest helpmate that still has a single solution. It is never the class's longest helpmate — those always have hundreds of solutions.
| class | men | sound | longest | positions at depth |
|---|
Puzzles
Every puzzle has exactly one solution. Play the whole line, both colours: drag Black's move, then White's reply, until mate. A wrong move snaps back.
Session: ten puzzles, easiest to hardest, drawn from the ones that match the filters. Solved so far: 0.
The corpus, table by table
| class | men | longest mate | positions with a helpmate | with a unique one | table |
|---|