Sudoku

Sudoku is a research project that uses Internet-connected computers to search for the smallest possible start configuration of Sudoku.

Sudoku is a very popular puzzle, so just google for it to get a description, programs etc. An important thing about Sudoku is that there always exists a solution and that this solution has to be unique! Writing a program which finds this solution is not very difficult, and you can find many such programs on the web.

An interesting question is, how few givens are sufficient such that a Sudoku still has a unique solution. A trivial lower bound is 8: assume only 7 numbers are given. Then in any solution you can interchange all occurrences of two non given digits, and thus there are always at least two different solutions. Surprisingly so far no better lower bound has been obtained by mathematical reasoning.

Thus the current range for the smallest number of clues (given numbers) that a Sudoku puzzle (with one unique solution) can have is 8 to 17. The goal of our project is to close this gap. To this end we start with 92248 sets with 8 primary givens (digits 1-8, representing all possibilities w.r.t. symmetry, relabeling etc.) and extend them by adding more givens, and checking for uniqueness.