Apparently generating "Finite Projective Planes". For context on how I got here, I went camping with my family and brought the game Spot It. My brother was analyzing it and came up with the same type of pattern.

When we got home he made a python script to generate these boards, but it was quite slow, so he half joked asking me to rewrite it in Rust.

I kinda struggled a bit since I didn't fully understand what it was doing. Near the end I even got a segfault using safe code😃! (i was spawning a thread with a large stack size, and allocating huge slices on its stack, rather than you know.. boxing the slice Lol.) When I finally got it working, it ended up being in the ballpark of a 23x speedup. Not bad for changing the language choice!

There's lots of room for improvement left for sure. The algorithm could benefit with some running statistics about cols/rows and the algorithm itself is quite naïve and could maybe be improved too :P