That's as may be, but nowhere in your program does it say that it should use either sse2 or avx2, which was the parent poster's point. At least that's what I un

That's as may be, but nowhere in your program does it say that it should use either sse2 or avx2, which was the parent poster's point. At least that's what I understood it to be. Technically you could have different code paths and inline asm, but that's not really specified by the C++ standard either.