Crate slicedvec

Storing vectors within vectors is convenient but means that each stored vector will allocate on the heap and drop when removed. SlicedVec stores constant-length segments within a single vector so that push within the storage capacity will not allocate and truncate will not deallocate from the heap. Benchmarks indicate that this strategy is not always faster for repeated cycles of push and swap_remove. This is likely because the overhead of swapping a larger number of elements. Vec within Vec only has to swap the pointers of the stored Vec objects whereas SlicedVec has to swap an entire segment of values. In a few cases, SlicedVec has proven about twice as fast, but you will need to test your cases. SlicedVec is nonetheless convenient for organizing segmented storage, such as a collection of image rows, and so on.

Example

use rand::{rngs::SmallRng, Rng, SeedableRng};
use slicedvec::SlicedVec;
let mut rng = SmallRng::from_entropy();
let mut x1 = SlicedVec::with_capacity(1000, 20);
x1.push_vec(
    std::iter::repeat_with(|| rng.gen())
    .take(20 * 1000)
    .collect::<Vec<_>>(),
);
let x1_insert: Vec<Vec<usize>> =
    std::iter::repeat_with(|| std::iter::repeat_with(|| rng.gen()).take(20).collect())
        .take(500)
        .collect();
for i in 0..500 { x1.swap_truncate(i) }
for i in 0..500 { x1.push(&x1_insert[i]) }

Macros

• slicedvec
  Contruct a SlicedVec from a list of arrays

Structs

• SlicedVec
  A segmented vector for iterating over slices of constant length.