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use crate::macros::{common_strct, for_current_bitness};
use crate::storage::{Storage, ViewStorage};
use super::{Root, UnionResult};
/// Mutable view to part of bigger disjoint set.
/// Useful for running union operations using multiple threads.
/// Contains nodes in range `lower_bound()..upper_bound()`.
pub struct ChunkMut<'owner>(pub(crate) common_strct!(ViewStorage, 'owner));
impl ChunkMut<'_> {
/// Split view into 2 non-overlapping parts at node with index.
/// Index is relative to owning disjoint set.
/// # Panics
/// If index is smaller than lower bound or greater or equal to upper bound.
#[must_use]
pub fn split_at(mut self, split_idx: usize) -> (Self, Self) {
unsafe {
// SAFETY: Returned lifetime is same as our lifetime.
// And our lifetime cannot ourlive owner.
self.0.split_at(split_idx)
}
}
/// Minimal value of node index allowed to be accessed using this chunk.
#[inline]
#[must_use]
pub fn lower_bound(&self) -> usize {
for_current_bitness!(&self.0.get_storage(); s; s.lower_bound())
}
/// Upper limit (exclusive) to node index allowed to be accessed using this chunk.
#[inline]
#[must_use]
pub fn upper_bound(&self) -> usize {
for_current_bitness!(&self.0.get_storage(); s; s.upper_bound())
}
/// Returns tag associated with node at index.
/// # Panics
/// If index less than lower bound or greater or equal to upper bound.
#[must_use]
pub fn get_root(&mut self, idx: usize) -> Root {
self.0.get_root(idx)
}
/// Performs union operation for subsets that contain nodes `idx0` and `idx1`.
/// Note that for mutable chunks this operation limited to bounds of chunk.
/// After calling this method, further splitting of chunk is not possible.
/// # Panics
/// If either `idx0` or `idx1` less than lower bound or greater or equal to upper bound.
pub fn union(&mut self, idx0: usize, idx1: usize) -> UnionResult {
self.0.union(idx0, idx1)
}
/// Same as [`DisjointSet::is_united`](crate::DisjointSet::is_united).
/// # Panics
/// If either `idx0` or `idx1` less than lower bound or greater or equal to upper bound.
#[must_use]
pub fn is_united(&mut self, idx0: usize, idx1: usize) -> bool {
self.0.is_united(idx0, idx1)
}
/// Same as [`DisjointSet::detach`](crate::DisjointSet::detach).
/// # Panics
/// If index is out of bounds.
pub fn detach(&mut self, idx: usize) {
self.0.detach(idx);
}
/// Eagerly apply path compression optimization.
/// Has complexity _O(n)_.
/// It compress paths only in current chunk.
/// This can be useful because if you call this for different chunks in separate threads,
/// most operations on owning disjoint set would be faster.
pub fn compress_paths(&mut self) {
self.0.compress_paths();
}
}
#[allow(clippy::let_underscore_untyped)]
#[cfg(test)]
mod tests {
use rstest::rstest;
use crate::{DisjointSet, Root};
#[test]
fn test_split() {
let mut djs = DisjointSet::new(10);
let (mut first, rest) = djs.split_at(4);
let (mut second, mut third) = rest.split_at(8);
assert_eq!(first.lower_bound(), 0);
assert_eq!(first.upper_bound(), 4);
assert_eq!(second.lower_bound(), 4);
assert_eq!(second.upper_bound(), 8);
assert_eq!(third.lower_bound(), 8);
assert_eq!(third.upper_bound(), 10);
std::thread::scope(|s| {
s.spawn(|| first.union(2, 3));
s.spawn(|| second.union(5, 6));
s.spawn(|| third.union(8, 9));
});
assert_eq!(second.get_root(6), Root(5));
assert_eq!(third.get_root(9), Root(8));
assert_eq!(first.get_root(3), Root(2));
assert!(djs.is_united(2, 3));
assert!(djs.is_united(5, 6));
assert!(djs.is_united(8, 9));
}
#[rstest]
#[should_panic]
fn test_split_bounds_check(#[values(1, 3, 9, 10, usize::MAX)] idx: usize) {
let mut djs = DisjointSet::new(8);
let (_, right) = djs.split_at(4);
let _: (_, _) = right.split_at(idx);
}
#[rstest]
#[should_panic]
fn test_get_root_bounds_check(#[values(1, 3, 9, 10, usize::MAX)] idx: usize) {
let mut djs = DisjointSet::new(8);
let (_, mut right) = djs.split_at(4);
let _: Root = right.get_root(idx);
}
#[rstest]
#[case(0, 8)]
#[case(0, 9)]
#[case(8, 0)]
#[case(9, 0)]
#[case(8, 9)]
#[case(9, 8)]
#[case(1, 5)]
#[should_panic]
fn test_union_bounds_check(#[case] idx0: usize, #[case] idx1: usize) {
let mut djs = DisjointSet::new(8);
let (_, mut right) = djs.split_at(4);
let _ = right.union(idx0, idx1);
}
}