#if defined(AVX2)

#define prefetch(a, i) _mm_prefetch(a+i, _MM_HINT_T0)

#else
#if defined(__GNUC__) || defined(__clang__)

#define prefetch(a, i) __builtin_prefetch(a+i, 0, 0)

#else

#define prefetch(a, i) (void)i

#endif
#endif