Is the included bench.c the right way to answer that question?

  1m random dist size 128 avg qsort 0.206549 blitsort 0.281630
  10m random dist size 32 avg qsort 2.963479 blitsort 4.394143
  100m random dist size 128 avg qsort 34.996847 blitsort 54.102616

It is, those numbers are less favorable than they are on my own machine.

The speed of your RAM memory is likely to have an influence on performance. My system is running at 2133MHz.

Interesting.

  16 GB 2133 MHz LPDDR3

Built with Apple clang version 12.0.5 (clang-1205.0.22.11) gcc -O3 bench.c

Blitsort can sort strings, but something like a 12 byte data structure would require an array with pointer references to sort.

As for the degradation against std:stable_sort:

5% slower at 1 million, 10% slower at 10 million, 20% slower at 100 million.

With sqrt n auxiliary you're looking at 2%, 4%, 6% slower.

Against qsort() it remains faster at 10 million, 3% slower at 100 million.

I am thinking more about sorting, say, 20-byte or 24-byte custom structs. Directly sorting arrays is probably faster than sorting pointers to arrays. At least in my applications, I rarely just sort numbers; I more often sort numbers along with other data associated with the numbers.

Hard to say which would be faster, I've made a mental note to benchmark sorting 16 byte long doubles through pointers as well as directly.

I never tried, but it should be possible (and relatively easy) to add custom sizes in the .h file.