xcvb

I only had a quick look at the code, but it looks like it's timing memory allocation. For example the sprintf part uses std::string str(100, '\0'). I'm not a C++ expert, but I believe this is essentially doing a malloc and memset of 100 bytes for every call to sprintf. So this is probably a poorly setup benchmark.

Looking at the code, it seems like it expects a string of the form "dddddddd?dddddd" where the '?' is any ascii character, and the code assumes the rest of the characters are ascii digits.

Specifically the line: `part2 = _pext_u64(part2, 0x0f000f0f0f0f0f0f);` seems to mask out that character.