I ran into CPU cache issues in a slightly different application 15+ years ago. I was working on indexing gigabytes of text on a mobile CPU (before smart phones

I ran into CPU cache issues in a slightly different application 15+ years ago. I was working on indexing gigabytes of text on a mobile CPU (before smart phones caused massive investment in such CPUs). Word normalization logic (e.g., sky/skies/sky's -> sky) was very slow, so I used a word cache which sped it up immensely. The initial version of the word cache cleared the entire cache when it hit a certain number of entries, just as a placeholder. When I got around to adding some LRU eviction logic, it became faster on our desktop simulator, but far slower on the embedded device (slower than with no word cache at all). The difference came down to the CPU cache size / strategy differences between the desktop and mobile CPUs. We ended up shipping the "dumb" word cache logic because it was so much faster in practice. The word cache eviction function was only two lines of code plus a large comment that acknowledged that "yes, this looks dumb" and imploring that the speed of any future improvements be compared to the dumb version on the target device. Testing real data on the hardware used in practice is incredibly important.