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Differential D9682

copies-rust: extract generic map merge logic from merge_copies_dict
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Authored by SimonSapin on Jan 6 2021, 9:12 AM.

Details

Reviewers
Alphare
Group Reviewers
hg-reviewers
Commits
rHG435d9fc72646: copies-rust: extract generic map merge logic from merge_copies_dict
rHG26d0acbc6cce: copies-rust: extract generic map merge logic from merge_copies_dict
Summary

This deduplicates the copy-tracing-specific logic

Diff Detail

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rHG Mercurial
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default
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No Unit Test Coverage

Event Timeline

SimonSapin created this revision.Jan 6 2021, 9:12 AM
baymax updated this revision to Diff 24682.Jan 8 2021, 6:16 PM

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Alphare accepted this revision.Jan 22 2021, 4:38 AM
Alphare added a subscriber: Alphare.

Thanks for the refactor, the comments are also clearer this way.

baymax updated this revision to Diff 25702.Feb 22 2021, 9:14 AM

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baymax updated this revision to Diff 25761.Feb 22 2021, 11:22 AM

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baymax updated this revision to Diff 25800.Feb 22 2021, 5:12 PM

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SimonSapin added a commit: rHG26d0acbc6cce: copies-rust: extract generic map merge logic from merge_copies_dict.Feb 24 2021, 11:03 AM
This revision was not accepted when it landed; it landed in state Needs Review.
Closed by commit rHG26d0acbc6cce: copies-rust: extract generic map merge logic from merge_copies_dict (authored by SimonSapin). · Explain Why
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathPackages
Mrust/hg-core/src/copy_tracing.rs (227 lines)
Mrust/hg-core/src/utils.rs (150 lines)

Diff 25761

rust/hg-core/src/copy_tracing.rs

use crate::utils::hg_path::HgPath; use crate::utils::hg_path::HgPath;
use crate::utils::hg_path::HgPathBuf; use crate::utils::hg_path::HgPathBuf;
use crate::Revision; use crate::Revision;
use crate::NULL_REVISION; use crate::NULL_REVISION;
use im_rc::ordmap::DiffItem;
use im_rc::ordmap::Entry; use im_rc::ordmap::Entry;
use im_rc::ordmap::OrdMap; use im_rc::ordmap::OrdMap;
use im_rc::OrdSet; use im_rc::OrdSet;
use std::cmp::Ordering; use std::cmp::Ordering;
use std::collections::HashMap; use std::collections::HashMap;
use std::convert::TryInto; use std::convert::TryInto;
/// merge two copies-mapping together, minor and major /// merge two copies-mapping together, minor and major
/// ///
/// In case of conflict, value from "major" will be picked, unless in some /// In case of conflict, value from "major" will be picked, unless in some
/// cases. See inline documentation for details. /// cases. See inline documentation for details.
fn merge_copies_dict( fn merge_copies_dict(
path_map: &TwoWayPathMap, path_map: &TwoWayPathMap,
current_merge: Revision, current_merge: Revision,
mut minor: InternalPathCopies, minor: InternalPathCopies,
mut major: InternalPathCopies, major: InternalPathCopies,
changes: &ChangedFiles, changes: &ChangedFiles,
) -> InternalPathCopies { ) -> InternalPathCopies {
// This closure exist as temporary help while multiple developper are use crate::utils::{ordmap_union_with_merge, MergeResult};
// actively working on this code. Feel free to re-inline it once this
// code is more settled. ordmap_union_with_merge(minor, major, |dest, src_minor, src_major| {
let cmp_value = let (pick, overwrite) = compare_value(
|dest: &PathToken, src_minor: &CopySource, src_major: &CopySource| {
compare_value(
path_map, path_map,
current_merge, current_merge,
changes, changes,
dest, dest,
src_minor, src_minor,
src_major, src_major,
) );
};
if minor.is_empty() {
major
} else if major.is_empty() {
minor
} else if minor.len() * 2 < major.len() {
// Lets says we are merging two InternalPathCopies instance A and B.
//
// If A contains N items, the merge result will never contains more
// than N values differents than the one in A
//
// If B contains M items, with M > N, the merge result will always
// result in a minimum of M - N value differents than the on in
// A
//
// As a result, if N < (M-N), we know that simply iterating over A will
// yield less difference than iterating over the difference
// between A and B.
//
// This help performance a lot in case were a tiny
// InternalPathCopies is merged with a much larger one.
for (dest, src_minor) in minor {
let src_major = major.get(&dest);
match src_major {
None => {
major.insert(dest, src_minor);
}
Some(src_major) => {
let (pick, overwrite) =
cmp_value(&dest, &src_minor, src_major);
if overwrite {
let src = match pick {
MergePick::Major => CopySource::new_from_merge(
current_merge,
src_major,
&src_minor,
),
MergePick::Minor => CopySource::new_from_merge(
current_merge,
&src_minor,
src_major,
),
MergePick::Any => CopySource::new_from_merge(
current_merge,
src_major,
&src_minor,
),
};
major.insert(dest, src);
} else {
match pick {
MergePick::Any | MergePick::Major => None,
MergePick::Minor => major.insert(dest, src_minor),
};
}
}
};
}
major
} else if major.len() * 2 < minor.len() {
// This use the same rational than the previous block.
// (Check previous block documentation for details.)
for (dest, src_major) in major {
let src_minor = minor.get(&dest);
match src_minor {
None => {
minor.insert(dest, src_major);
}
Some(src_minor) => {
let (pick, overwrite) =
cmp_value(&dest, src_minor, &src_major);
if overwrite { if overwrite {
let src = match pick { let (winner, loser) = match pick {
MergePick::Major => CopySource::new_from_merge( MergePick::Major | MergePick::Any => (src_major, src_minor),
current_merge, MergePick::Minor => (src_minor, src_major),
&src_major,
src_minor,
),
MergePick::Minor => CopySource::new_from_merge(
current_merge,
src_minor,
&src_major,
),
MergePick::Any => CopySource::new_from_merge(
current_merge,
&src_major,
src_minor,
),
};
minor.insert(dest, src);
} else {
match pick {
MergePick::Any | MergePick::Minor => None,
MergePick::Major => minor.insert(dest, src_major),
};
}
}
}; };
} MergeResult::UseNewValue(CopySource::new_from_merge(
minor
} else {
let mut override_minor = Vec::new();
let mut override_major = Vec::new();
let mut to_major = |k: &PathToken, v: &CopySource| {
override_major.push((k.clone(), v.clone()))
};
let mut to_minor = |k: &PathToken, v: &CopySource| {
override_minor.push((k.clone(), v.clone()))
};
// The diff function leverage detection of the identical subpart if
// minor and major has some common ancestors. This make it very
// fast is most case.
//
// In case where the two map are vastly different in size, the current
// approach is still slowish because the iteration will iterate over
// all the "exclusive" content of the larger on. This situation can be
// frequent when the subgraph of revision we are processing has a lot
// of roots. Each roots adding they own fully new map to the mix (and
// likely a small map, if the path from the root to the "main path" is
// small.
//
// We could do better by detecting such situation and processing them
// differently.
for d in minor.diff(&major) {
match d {
DiffItem::Add(k, v) => to_minor(k, v),
DiffItem::Remove(k, v) => to_major(k, v),
DiffItem::Update { old, new } => {
let (dest, src_major) = new;
let (_, src_minor) = old;
let (pick, overwrite) =
cmp_value(dest, src_minor, src_major);
if overwrite {
let src = match pick {
MergePick::Major => CopySource::new_from_merge(
current_merge,
src_major,
src_minor,
),
MergePick::Minor => CopySource::new_from_merge(
current_merge,
src_minor,
src_major,
),
MergePick::Any => CopySource::new_from_merge(
current_merge, current_merge,
src_major, winner,
src_minor, loser,
), ))
};
to_minor(dest, &src);
to_major(dest, &src);
} else { } else {
match pick { match pick {
MergePick::Major => to_minor(dest, src_major), MergePick::Any | MergePick::Major => {
MergePick::Minor => to_major(dest, src_minor), MergeResult::UseRightValue
// If the two entry are identical, no need to do
// anything (but diff should not have yield them)
MergePick::Any => unreachable!(),
}
} }
MergePick::Minor => MergeResult::UseLeftValue,
} }
};
}
let updates;
let mut result;
if override_major.is_empty() {
result = major
} else if override_minor.is_empty() {
result = minor
} else {
if override_minor.len() < override_major.len() {
updates = override_minor;
result = minor;
} else {
updates = override_major;
result = major;
}
for (k, v) in updates {
result.insert(k, v);
}
}
result
} }
})
} }
/// represent the side that should prevail when merging two /// represent the side that should prevail when merging two
/// InternalPathCopies /// InternalPathCopies
enum MergePick { enum MergePick {
/// The "major" (p1) side prevails /// The "major" (p1) side prevails
Major, Major,
/// The "minor" (p2) side prevails /// The "minor" (p2) side prevails

rust/hg-core/src/utils.rs

// utils module // utils module
// //
// Copyright 2019 Raphaël Gomès <rgomes@octobus.net> // Copyright 2019 Raphaël Gomès <rgomes@octobus.net>
// //
// This software may be used and distributed according to the terms of the // This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version. // GNU General Public License version 2 or any later version.
//! Contains useful functions, traits, structs, etc. for use in core. //! Contains useful functions, traits, structs, etc. for use in core.
use crate::errors::{HgError, IoErrorContext}; use crate::errors::{HgError, IoErrorContext};
use crate::utils::hg_path::HgPath; use crate::utils::hg_path::HgPath;
use im_rc::ordmap::DiffItem;
use im_rc::ordmap::OrdMap;
use std::{io::Write, ops::Deref}; use std::{io::Write, ops::Deref};
pub mod files; pub mod files;
pub mod hg_path; pub mod hg_path;
pub mod path_auditor; pub mod path_auditor;
/// Useful until rust/issues/56345 is stable /// Useful until rust/issues/56345 is stable
/// ///
} }
pub fn current_exe() -> Result<std::path::PathBuf, HgError> { pub fn current_exe() -> Result<std::path::PathBuf, HgError> {
std::env::current_exe().map_err(|error| HgError::IoError { std::env::current_exe().map_err(|error| HgError::IoError {
error, error,
context: IoErrorContext::CurrentExe, context: IoErrorContext::CurrentExe,
}) })
} }
pub(crate) enum MergeResult<V> {
UseLeftValue,
UseRightValue,
UseNewValue(V),
}
/// Return the union of the two given maps,
/// calling `merge(key, left_value, right_value)` to resolve keys that exist in
/// both.
///
/// CC https://github.com/bodil/im-rs/issues/166
pub(crate) fn ordmap_union_with_merge<K, V>(
left: OrdMap<K, V>,
right: OrdMap<K, V>,
mut merge: impl FnMut(&K, &V, &V) -> MergeResult<V>,
) -> OrdMap<K, V>
where
K: Clone + Ord,
V: Clone + PartialEq,
{
if left.ptr_eq(&right) {
// One of the two maps is an unmodified clone of the other
left
} else if left.len() / 2 > right.len() {
// When two maps have different sizes,
// their size difference is a lower bound on
// how many keys of the larger map are not also in the smaller map.
// This in turn is a lower bound on the number of differences in
// `OrdMap::diff` and the "amount of work" that would be done
// by `ordmap_union_with_merge_by_diff`.
//
// Here `left` is more than twice the size of `right`,
// so the number of differences is more than the total size of
// `right`. Therefore an algorithm based on iterating `right`
// is more efficient.
//
// This helps a lot when a tiny (or empty) map is merged
// with a large one.
ordmap_union_with_merge_by_iter(left, right, merge)
} else if left.len() < right.len() / 2 {
// Same as above but with `left` and `right` swapped
ordmap_union_with_merge_by_iter(right, left, |key, a, b| {
// Also swapped in `merge` arguments:
match merge(key, b, a) {
MergeResult::UseNewValue(v) => MergeResult::UseNewValue(v),
// … and swap back in `merge` result:
MergeResult::UseLeftValue => MergeResult::UseRightValue,
MergeResult::UseRightValue => MergeResult::UseLeftValue,
}
})
} else {
// For maps of similar size, use the algorithm based on `OrdMap::diff`
ordmap_union_with_merge_by_diff(left, right, merge)
}
}
/// Efficient if `right` is much smaller than `left`
fn ordmap_union_with_merge_by_iter<K, V>(
mut left: OrdMap<K, V>,
right: OrdMap<K, V>,
mut merge: impl FnMut(&K, &V, &V) -> MergeResult<V>,
) -> OrdMap<K, V>
where
K: Clone + Ord,
V: Clone,
{
for (key, right_value) in right {
match left.get(&key) {
None => {
left.insert(key, right_value);
}
Some(left_value) => match merge(&key, left_value, &right_value) {
MergeResult::UseLeftValue => {}
MergeResult::UseRightValue => {
left.insert(key, right_value);
}
MergeResult::UseNewValue(new_value) => {
left.insert(key, new_value);
}
},
}
}
left
}
/// Fallback when both maps are of similar size
fn ordmap_union_with_merge_by_diff<K, V>(
mut left: OrdMap<K, V>,
mut right: OrdMap<K, V>,
mut merge: impl FnMut(&K, &V, &V) -> MergeResult<V>,
) -> OrdMap<K, V>
where
K: Clone + Ord,
V: Clone + PartialEq,
{
// (key, value) pairs that would need to be inserted in either map
// in order to turn it into the union.
//
// TODO: if/when https://github.com/bodil/im-rs/pull/168 is accepted,
// change these from `Vec<(K, V)>` to `Vec<(&K, Cow<V>)>`
// with `left_updates` only borrowing from `right` and `right_updates` from
// `left`, and with `Cow::Owned` used for `MergeResult::UseNewValue`.
//
// This would allow moving all `.clone()` calls to after we’ve decided
// which of `right_updates` or `left_updates` to use
// (value ones becoming `Cow::into_owned`),
// and avoid making clones we don’t end up using.
let mut left_updates = Vec::new();
let mut right_updates = Vec::new();
for difference in left.diff(&right) {
match difference {
DiffItem::Add(key, value) => {
left_updates.push((key.clone(), value.clone()))
}
DiffItem::Remove(key, value) => {
right_updates.push((key.clone(), value.clone()))
}
DiffItem::Update {
old: (key, left_value),
new: (_, right_value),
} => match merge(key, left_value, right_value) {
MergeResult::UseLeftValue => {
right_updates.push((key.clone(), left_value.clone()))
}
MergeResult::UseRightValue => {
left_updates.push((key.clone(), right_value.clone()))
}
MergeResult::UseNewValue(new_value) => {
left_updates.push((key.clone(), new_value.clone()));
right_updates.push((key.clone(), new_value))
}
},
}
}
if left_updates.len() < right_updates.len() {
for (key, value) in left_updates {
left.insert(key, value);
}
left
} else {
for (key, value) in right_updates {
right.insert(key, value);
}
right
}
}