PackedVec
A PackedVec
stores vectors of integers
efficiently while providing an API similar to Vec
. The basic idea is to store
each element using the minimum number of bits needed to represent every element
in the Vec
. For example, if we have a Vec<u64>
with elements [20, 30, 140],
every element wastes most of its 64 bits: 7 bits is sufficient to represent the
range of elements in the vector. Given this input vector, PackedVec
stores
each elements using exactly 7 bits, saving substantial memory. For vectors which
often contain small ranges of numbers, and which are created rarely, but read
from frequently, this can be a significant memory and performance win.
Examples
PackedVec
has two main API differences from Vec
: a PackedVec
is created
from a Vec
; and a PackedVec
returns values rather than references. Both
points can be seen in this example:
use PackedVec;
let v = vec!;
let pv = new;
assert_eq!;
assert_eq!;
assert_eq!;
assert_eq!;