Function scale_vol_assign 

pub fn scale_vol_assign<T>(backend: ComputeBackend, y: &mut VolField<T>, s: f64)
where
    T: Copy + Send + Sync + Mul<f64, Output = T>,

In-place uniform scaling of a volume field, y *= s. Allocation-free, name-preserving. Units: the field becomes [y]*[s].