Link of the week  How low can a Sudoku go?




There are two ways to solve a Sudoku: by hand, or by writing a computer program to do it for you. For "ordinary" Sudokuwhere you begin with 25 to 30 "clue" numbersthis is a relatively simple proposition. But what happens when you start with half as many clues? Can you still solve a Sudoku which begins with only ten clues? What about five clues? How low can a Sudoku go while still ensuring it has only one unique solution? Running the numbers So far, all known minimal Sudokus with a unique solution begin with 17 "clue" numbers. Further, any puzzles with fewer than eight clues have resulted in at least two different solutions. Thus, minimal Sudokus are thought to require 817 numbers. A new BOINCpowered distributed computing projectSudokuis determined to close this gap, aiming to discover the smallest possible start configuration required to solve a Sudoku that has only one, unique solution. Those involved in the project say initial evaluations have reduced the range to 1117 initial clues; the next step is to use volunteer computing to increase this lower number, until one user either finds a new minimal example, or it can be shown that no such examples exist for up to 16 givens. You can participate by downloading and running the BOINC program on your computer. 