I have this basic cross product declared like this in my kernel:
inline const Vec3 Cross(const Vec3 v1, const Vec3 v2)
{
Vec3 v;
v.x = v1.y*v2.z - v2.y*v1.z;
v.y = v1.z*v2.x - v2.z*v1.x;
v.z = v1.x*v2.y - v2.x*v1.y;
return v;
}
Though I get that floating point operations are generally speaking
order-dependent I was expecting given the simplicity of a cross product
that we'd still find Cross(v0,v1) = -Cross(v1,v0) yet when I build for the
avx2 target this is not what I'm seeing. For all other targets SSE2-AVX1 it
is working in the sense that the above property holds true.
Right now I'm working around by doing sort of a 96bit check if v0>v1 and if
it is then I swap the inputs but it's adding overhead. So I wanted to ask
if you guys would consider it a big or not on ispc side? Or is it simply
that I can't reasonably expect Cross(v0,v1) = -Cross(v1,v0) for the
generated code.
Thank you,
Morten S. Mikkelsen
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