On most Linux distributions and when the file is mmap'd, if you run it a second time the data will still be in RAM and not have to be read from disk. This gets

On most Linux distributions and when the file is mmap'd, if you run it a second time the data will still be in RAM and not have to be read from disk. This gets the runtime down to 1.1s for this AMD 2950x (https://github.com/gunnarmorling/1brc/discussions/46#discussioncomment-8028029 https://github.com/gunnarmorling/1brc/discussions/46#discuss...). With SIMD and certain assumptions about the input this can seemingly be further reduced to well under a second, eg see https://github.com/gunnarmorling/1brc/discussions/138 https://github.com/gunnarmorling/1brc/discussions/138.