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Drop bubble_sort

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While using it results in slightly slammer binaries, it's not deemed
worth it to add yet another sort algorithm to the standard library.
select_nth_unstable has bigger binary-size problems.
This commit is contained in:
Lukas Bergdoll 2024-09-04 18:58:44 +02:00
parent 00eca77b72
commit f2d4198d6e
3 changed files with 3 additions and 41 deletions
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1
library/core/src/slice/sort/mod.rs
View File

@ -5,5 +5,4 @@ pub mod stable;
pub mod unstable;
pub(crate) mod select;
#[cfg(not(feature = "optimize_for_size"))]
pub(crate) mod shared;

39
library/core/src/slice/sort/select.rs
View File

@ -9,7 +9,6 @@
use crate::mem::{self, SizedTypeProperties};
#[cfg(not(feature = "optimize_for_size"))]
use crate::slice::sort::shared::pivot::choose_pivot;
#[cfg(not(feature = "optimize_for_size"))]
use crate::slice::sort::shared::smallsort::insertion_sort_shift_left;
use crate::slice::sort::unstable::quicksort::partition;
@ -176,14 +175,8 @@ fn median_of_medians<T, F: FnMut(&T, &T) -> bool>(mut v: &mut [T], is_less: &mut
loop {
if v.len() <= INSERTION_SORT_THRESHOLD {
if v.len() >= 2 {
cfg_if! {
if #[cfg(feature = "optimize_for_size")] {
bubble_sort(v, is_less);
} else {
insertion_sort_shift_left(v, 1, is_less);
}
}
}
return;
}
@ -314,35 +307,3 @@ fn median_idx<T, F: FnMut(&T, &T) -> bool>(
}
b
}
// It's possible to re-use the insertion sort in the smallsort module, but with optimize_for_size it
// would clutter that module with cfg statements and make it generally harder to read and develop.
// So to decouple things and simplify it, we use an even smaller bubble sort.
#[cfg(feature = "optimize_for_size")]
fn bubble_sort<T, F: FnMut(&T, &T) -> bool>(v: &mut [T], is_less: &mut F) {
use crate::ptr;
let mut n = v.len();
let v_base = v.as_mut_ptr();
while n > 1 {
let loop_n = n;
n = 0;
for i in 1..loop_n {
// SAFETY: The loop construction implies that `i` and `i - 1` will always be in-bounds.
unsafe {
// Even if `is_less` erroneously always returns true, we are guaranteed that `n`
// reduces by one each out loop iteration, because `1..n` is exclusive. This
// guarantees a bounded run-time should `Ord` be implemented incorrectly.
let v_i = v_base.add(i);
let v_i_minus_one = v_base.add(i - 1);
if is_less(&*v_i, &*v_i_minus_one) {
ptr::swap_nonoverlapping(v_i, v_i_minus_one, 1);
n = i;
}
}
}
}
}

2
library/core/src/slice/sort/shared/mod.rs
View File

@ -1,3 +1,5 @@
#![cfg_attr(feature = "optimize_for_size", allow(dead_code))]
use crate::marker::Freeze;
pub(crate) mod pivot;