EsoErik

Glenn Fowler of AT&T Labs wrote an excellent Sudoku application - Sudocoup - which I have envied for some time.  As I developed my own Sudoku solver, I compared its execution time for various puzzles to that of Sudocoup.

In April, Sudocoup could solve 9x9 puzzles that mine could not.  By June, my solver could do any puzzle up to 36x36 - but far slower than Sudocoup.  In July, I implemented a raft of additional constraint logic reduction routines that allowed solving 64x64 puzzles in a few minutes - as compared to the seconds required by Sudocoup.  144x144 remained completely out of reach.

However, I finished implementing single-node chain reduction for my solver, which I named Arcterik Sudoku.  Arcterik Sudoku solves this 256x256 puzzle in 0.635 seconds, whereas  Sudocoup requires 3 minutes, 26 seconds.

So, I've hit the faster than Sudocoup milestone that seemed unreachable for so long.  My ultimate goal for this project, aside from sharpening my graph theory and learning some new things, is to handle 65536x65536 puzzles in reasonable time.