Auto merge of #86898 - the8472:path-cmp, r=dtolnay
Add fast path for Path::cmp that skips over long shared prefixes ``` # before test path::tests::bench_path_cmp_fast_path_buf_sort ... bench: 60,811 ns/iter (+/- 865) test path::tests::bench_path_cmp_fast_path_long ... bench: 6,459 ns/iter (+/- 275) test path::tests::bench_path_cmp_fast_path_short ... bench: 1,777 ns/iter (+/- 34) # after test path::tests::bench_path_cmp_fast_path_buf_sort ... bench: 38,140 ns/iter (+/- 211) test path::tests::bench_path_cmp_fast_path_long ... bench: 1,471 ns/iter (+/- 24) test path::tests::bench_path_cmp_fast_path_short ... bench: 1,106 ns/iter (+/- 9) ```
This commit is contained in:
commit
bcfd3f7e88
2 changed files with 108 additions and 7 deletions
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@ -962,7 +962,7 @@ impl cmp::Eq for Components<'_> {}
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impl<'a> cmp::PartialOrd for Components<'a> {
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#[inline]
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fn partial_cmp(&self, other: &Components<'a>) -> Option<cmp::Ordering> {
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Iterator::partial_cmp(self.clone(), other.clone())
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Some(compare_components(self.clone(), other.clone()))
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}
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}
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@ -970,10 +970,43 @@ impl<'a> cmp::PartialOrd for Components<'a> {
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impl cmp::Ord for Components<'_> {
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#[inline]
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fn cmp(&self, other: &Self) -> cmp::Ordering {
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Iterator::cmp(self.clone(), other.clone())
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compare_components(self.clone(), other.clone())
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}
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}
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fn compare_components(mut left: Components<'_>, mut right: Components<'_>) -> cmp::Ordering {
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// Fast path for long shared prefixes
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//
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// - compare raw bytes to find first mismatch
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// - backtrack to find separator before mismatch to avoid ambiguous parsings of '.' or '..' characters
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// - if found update state to only do a component-wise comparison on the remainder,
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// otherwise do it on the full path
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//
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// The fast path isn't taken for paths with a PrefixComponent to avoid backtracking into
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// the middle of one
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if left.prefix.is_none() && right.prefix.is_none() && left.front == right.front {
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// this might benefit from a [u8]::first_mismatch simd implementation, if it existed
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let first_difference =
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match left.path.iter().zip(right.path.iter()).position(|(&a, &b)| a != b) {
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None if left.path.len() == right.path.len() => return cmp::Ordering::Equal,
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None => left.path.len().min(right.path.len()),
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Some(diff) => diff,
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};
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if let Some(previous_sep) =
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left.path[..first_difference].iter().rposition(|&b| left.is_sep_byte(b))
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{
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let mismatched_component_start = previous_sep + 1;
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left.path = &left.path[mismatched_component_start..];
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left.front = State::Body;
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right.path = &right.path[mismatched_component_start..];
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right.front = State::Body;
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}
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}
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Iterator::cmp(left, right)
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}
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/// An iterator over [`Path`] and its ancestors.
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///
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/// This `struct` is created by the [`ancestors`] method on [`Path`].
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@ -1704,7 +1737,7 @@ impl cmp::Eq for PathBuf {}
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impl cmp::PartialOrd for PathBuf {
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#[inline]
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fn partial_cmp(&self, other: &PathBuf) -> Option<cmp::Ordering> {
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self.components().partial_cmp(other.components())
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Some(compare_components(self.components(), other.components()))
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}
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}
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@ -1712,7 +1745,7 @@ impl cmp::PartialOrd for PathBuf {
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impl cmp::Ord for PathBuf {
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#[inline]
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fn cmp(&self, other: &PathBuf) -> cmp::Ordering {
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self.components().cmp(other.components())
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compare_components(self.components(), other.components())
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}
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}
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@ -2686,7 +2719,7 @@ impl fmt::Display for Display<'_> {
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impl cmp::PartialEq for Path {
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#[inline]
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fn eq(&self, other: &Path) -> bool {
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self.components().eq(other.components())
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self.components() == other.components()
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}
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}
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@ -2706,7 +2739,7 @@ impl cmp::Eq for Path {}
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impl cmp::PartialOrd for Path {
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#[inline]
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fn partial_cmp(&self, other: &Path) -> Option<cmp::Ordering> {
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self.components().partial_cmp(other.components())
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Some(compare_components(self.components(), other.components()))
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}
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}
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@ -2714,7 +2747,7 @@ impl cmp::PartialOrd for Path {
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impl cmp::Ord for Path {
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#[inline]
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fn cmp(&self, other: &Path) -> cmp::Ordering {
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self.components().cmp(other.components())
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compare_components(self.components(), other.components())
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}
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}
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@ -1,7 +1,9 @@
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use super::*;
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use crate::collections::BTreeSet;
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use crate::rc::Rc;
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use crate::sync::Arc;
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use core::hint::black_box;
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macro_rules! t(
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($path:expr, iter: $iter:expr) => (
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@ -1392,3 +1394,69 @@ fn into_rc() {
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assert_eq!(&*rc2, path);
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assert_eq!(&*arc2, path);
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}
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#[test]
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fn test_ord() {
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macro_rules! ord(
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($ord:ident, $left:expr, $right:expr) => ( {
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assert_eq!(Path::new($left).cmp(&Path::new($right)), core::cmp::Ordering::$ord);
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});
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);
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ord!(Less, "1", "2");
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ord!(Less, "/foo/bar", "/foo./bar");
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ord!(Less, "foo/bar", "foo/bar.");
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ord!(Equal, "foo/./bar", "foo/bar/");
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ord!(Equal, "foo/bar", "foo/bar/");
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ord!(Equal, "foo/bar", "foo/bar/.");
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ord!(Equal, "foo/bar", "foo/bar//");
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}
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#[bench]
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fn bench_path_cmp_fast_path_buf_sort(b: &mut test::Bencher) {
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let prefix = "my/home";
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let mut paths: Vec<_> =
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(0..1000).map(|num| PathBuf::from(prefix).join(format!("file {}.rs", num))).collect();
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paths.sort();
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b.iter(|| {
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black_box(paths.as_mut_slice()).sort_unstable();
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});
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}
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#[bench]
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fn bench_path_cmp_fast_path_long(b: &mut test::Bencher) {
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let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
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let paths: Vec<_> =
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(0..1000).map(|num| PathBuf::from(prefix).join(format!("file {}.rs", num))).collect();
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let mut set = BTreeSet::new();
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paths.iter().for_each(|p| {
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set.insert(p.as_path());
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});
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b.iter(|| {
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set.remove(paths[500].as_path());
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set.insert(paths[500].as_path());
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});
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}
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#[bench]
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fn bench_path_cmp_fast_path_short(b: &mut test::Bencher) {
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let prefix = "my/home";
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let paths: Vec<_> =
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(0..1000).map(|num| PathBuf::from(prefix).join(format!("file {}.rs", num))).collect();
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let mut set = BTreeSet::new();
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paths.iter().for_each(|p| {
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set.insert(p.as_path());
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});
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b.iter(|| {
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set.remove(paths[500].as_path());
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set.insert(paths[500].as_path());
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});
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}
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