Function parallel_map_reduce_indexed 

pub fn parallel_map_reduce_indexed<R, T, M, Red>(
    range: R,
    chunk_size: usize,
    mapper: M,
    reducer: Red,
) -> T
where
    R: Iterator<Item = usize> + Send,
    T: Send + Clone,
    M: Fn(&[usize]) -> T + Sync + Send,
    Red: Fn(T, T) -> T + Sync + Send,

Parallel map-reduce operation on indexed chunks

This function takes a range of indices, splits them into chunks of the specified size, processes each chunk in parallel using the mapper function, and then reduces the results using the reducer function.

Arguments

• range - The range of indices to process (e.g., 0..n)
• chunk_size - Size of each chunk for parallel processing
• mapper - Function that processes a slice of indices and returns a result
• reducer - Function that combines two results into one

Returns

The final reduced result