I was initially skeptical of the 2.5s for the SUM base case but after a bit of experimenting I concluded the following. Note this is for the SUM base case only

I was initially skeptical of the 2.5s for the SUM base case but after a bit of experimenting I concluded the following. Note this is for the SUM base case only. The whole file is loaded into memory for my tests. MMAP'd from HDD 1st run - 47s MMAP'd from HDD 2nd run - 1.35s (OS caches pages in memory) MMAP'd from NVMe 1st run - 6.5s (OS Caches dropped) MMAp'd from NVMe 2nd run 1.35s (OS cached again)