Just the straight/naive rewrite was ~3 times faster for my benchmark (which was running the program on the real dataset) and then I went down the rabbit hole and optimized it further and ended up ~5 times faster. Then slapped Rayon on top and got another ~2-3x depending on the number of cores and disk speed (the problem wasn't embarrassingly parallel, but still got a nice speedup).
Of course, all of this was mostly unneeded, but I just wanted to find out what am I getting myself into, and I was very happy with the result. My move to Rust was mostly not because of speed, but I still needed a fast language (where OCaml qualifies). This was also before the days of multicore OCaml, so nowadays it would matter even less.
> straight/naive rewrite was ~3 times faster
How much of that do you think comes from reduced allocations/indirections? Now I really want to try out OxCaml and see if I can approximate this speedup by picking up low hanging fruits.
I would imagine most of it, because the program in question mostly does parsing and ETL.
Do you have a ballpark value of how much faster Rust is? Also I wonder if OxCaml will be roughly as fast with less effort.