Macro batch_iter_mut 

macro_rules! batch_iter_mut {
    ($e: expr, $c: expr) => { ... };
    ($e: expr, $min_batch_size: expr, $c: expr) => { ... };
}

Applies a procedure to the provided slice either in a single thread or multiple threads based on whether concurrent feature is enabled.

When concurrent feature is enabled, breaks the slice into batches and processes each batch in a separate thread; otherwise, the entire slice is processed as a single batch in one thread. Optionally, min_batch_size can be used to specify the minimum size of the resulting batches.