如何通过avx取模int64

Question

I want to implement 5%3=2 by avx.

normal: int64 x = a % b

math: int64 x = a-((double)a/b)*b

avx:
__m256 tmp1 = _mm256_cvtepi32_ps(data);

I need convert a big number from int64 to float, then float overflow.

how to solve overflow when convert int64 to float?

Answer 1

In common case your way is wrong. 'double' type has 52-bit mantissa which obviously isn't sufficient to represent exactly an arbitrary 64-bit integer. You might get wrong results.

'long double' type would be suitable, but it's only avaliable with x87, not SIMD.