Function elementwise_kernel 

pub fn elementwise_kernel<F: Float + CubeElement + LaunchArg>(
    input: &[F],
    output: &mut [F],
    floor: F,
    op: u32,
)

One function of each sample (op, fixed at compile time): 0 |x|, 1 x², 2 √max(x, 0), 3 log₁₀ max(|x|, floor).