Er, the real "hardest Sudoku"

Following the comment from Malcom below, I've run my Sudoku solver against the real "AL Escargot"...

Using Saxon 8.9.0.3b from the command line with the -3 option (to discount java startup time) the average time across three runs is 2213ms... which isn't bad at all.

This is when I just solve the puzzle starting at the top-left - if I turn on the ordering feature where empty cells are processing by least number of possibilities first, then the time dramatically increases to ~58 seconds, which shows why Sudoku is NP-complete.

If you're interested the solution it produced is:


1, 6, 2,   8, 5, 7,   4, 9, 3
5, 3, 4,   1, 2, 9,   6, 7, 8
7, 8, 9,   6, 4, 3,   5, 2, 1

4, 7, 5,   3, 1, 2,   9, 8, 6
9, 1, 3,   5, 8, 6,   7, 4, 2
6, 2, 8,   7, 9, 4,   1, 3, 5

3, 5, 6,   4, 7, 8,   2, 1, 9,
2, 4, 1,   9, 3, 5,   8, 6, 7,
8, 9, 7,   2, 6, 1,   3, 5, 4,


The Worlds Hardest Sudoku

A mathematician claims to have penned the world's hardest Sudoku puzzle.

Running it through my Sudoku Solver it took ~24 seconds on my work machine (most puzzles are sub 1 second on the same machine) so I would think it must be reasonably hard.