Function chunks_mut_init 

pub fn chunks_mut_init<T, S, I, F>(
    data: &mut [T],
    chunk_len: usize,
    min_len: usize,
    init: I,
    f: F,
)
where
    T: Send,
    S: Send,
    I: Fn() -> S + Send + Sync,
    F: Fn(&mut S, usize, &mut [T]) + Send + Sync,

chunks_mut with a per-task scratch value.