Function bdiv_inplace_f32 

pub fn bdiv_inplace_f32(
    div: &mut [f32],
    gx: &[f32],
    gy: &[f32],
    gz: &[f32],
    nx: usize,
    ny: usize,
    nz: usize,
    vsx: f32,
    vsy: f32,
    vsz: f32,
)

Backward divergence operator (in-place, f32) Uses zero boundary conditions (matching Julia)