Okay, we think it’s largest ever, but at least it definitely is big. On July 24, 2024 a Sudoku (3600×3600 grid) with 6.2 million blanks was solved in 6 days. A few days before on July 18, 2024 a Sudoku (3025×3025 grid) with 4.4 million blanks was solved in 2.5 days. Want to see a step-by-step solution? Download the solution from the archive page! Yes, these are the ridiculously simple Sudokus that can be solved with hidden singles only. Even still, such a feat would take a traditional backtracking code a long time. Actually, it would run a lot longer – assuming it didn’t run out of memory first.
What does such a puzzle look like? Print a 4 by 4 box in one square inch. It would take a 75 ft by 75 ft banner to display the entire Sudoku grid (3600×3600). Even though the patterns are easy, it’s difficult to see the patterns.
How does this “biggest solved Sudoku ever” compare to the Guinness book of World Records? The largest multi-sudoku puzzle consists of 280 sudoku grids (approximately 17,920 blanks) which is about 247 times smaller than what we solved in 2.5 days or 346 times smaller than the 3600×3600 puzzle.
The computer is currently crunching on a box dimension 65 puzzle (4225×4225 grid). The ETA for the solution is ~10 days. Meanwhile, we are exploring CUDA solvers to help speed up the puzzle solving process. So far, no such luck. RIght now the overhead to startup the CUDA solver makes it slower than the multicore solver. We haven’t given up yet.