I was able to get a little bit faster than the multithreaded version with a single thread using page-aligned reads and Grand Central Dispatch for asynchronous read operations: https://github.com/healeycodes/counting-words-at-simd-speed/...

This was a nice opportunity to learn about Grand Central Dispatch through AI for me as well. I knew about the page alignment and async read techniques but not on OSX.

Edit: actually you can get even faster with mmap https://github.com/healeycodes/counting-words-at-simd-speed/...