Regarding #17

Official boolean indexing code is
https://github.com/numpy/numpy/blob/cf1306a842d7b1064270bd06951a485121e60816/numpy/core/src/multiarray/mapping.c#L1010

SIMD function is
https://github.com/numpy/numpy/blob/45bc13e6d922690eea43b9d807d476e0f243f836/numpy/core/src/umath/loops_comparison.dispatch.c.src#L36