in crates/ratchet-core/src/ops/unary.rs [305:318]
fn kernel_element(&self, _dst: &Tensor) -> KernelElement {
let UnaryKernels::Standard(inner) = self;
let a_rank = &inner.input.shape().rank();
let N = &inner.input.shape()[a_rank - 1];
if N % 4 == 0 {
KernelElement::Vec4
} else if N % 2 == 0 {
KernelElement::Vec2
} else {
KernelElement::Scalar
}
}