Function parallel_partition 

pub fn parallel_partition<T, I, K, V, KeyFn, ValFn>(
    items: I,
    key_fn: KeyFn,
    val_fn: ValFn,
) -> HashMap<K, Vec<V>>
where
    T: Send,
    K: Send + Eq + Hash + Clone,
    V: Send,
    I: ParallelIterator<Item = T>,
    KeyFn: Fn(&T) -> K + Sync + Send,
    ValFn: Fn(T) -> V + Sync + Send,

Partition items into groups based on a key extractor.

Groups items with the same key into separate vectors. The keys must be hashable and cloneable.

Example

use grafeo_core::execution::parallel::fold::parallel_partition;
use rayon::prelude::*;

let items = vec![(1, "a"), (2, "b"), (1, "c"), (2, "d")];
let groups = parallel_partition(items.into_par_iter(), |(k, _)| *k, |(_, v)| v);

assert_eq!(groups[&1].len(), 2);
assert_eq!(groups[&2].len(), 2);