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Create an arena for package names (#242)
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@Eh2406
Eh2406 authored Nov 20, 2024
1 parent 4bde6d6 commit 4ac6c42
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Showing 7 changed files with 294 additions and 221 deletions.
43 changes: 43 additions & 0 deletions src/internal/arena.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,8 @@ use std::hash::{Hash, Hasher};
use std::marker::PhantomData;
use std::ops::{Index, Range};

type FnvIndexSet<V> = indexmap::IndexSet<V, rustc_hash::FxBuildHasher>;

/// The index of a value allocated in an arena that holds `T`s.
///
/// The Clone, Copy and other traits are defined manually because
Expand Down Expand Up @@ -124,3 +126,44 @@ impl<T> Index<Range<Id<T>>> for Arena<T> {
&self.data[(id.start.raw as usize)..(id.end.raw as usize)]
}
}

/// Yet another index-based arena. This one de-duplicates entries by hashing.
///
/// An arena is a kind of simple grow-only allocator, backed by a `Vec`
/// where all items have the same lifetime, making it easier
/// to have references between those items.
/// In this case the `Vec` is inside a `IndexSet` allowing fast lookup by value not just index.
/// They are all dropped at once when the arena is dropped.
#[derive(Clone, PartialEq, Eq)]
pub struct HashArena<T: Hash + Eq> {
data: FnvIndexSet<T>,
}

impl<T: Hash + Eq + fmt::Debug> fmt::Debug for HashArena<T> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("Arena")
.field("len", &self.data.len())
.field("data", &self.data)
.finish()
}
}

impl<T: Hash + Eq> HashArena<T> {
pub fn new() -> Self {
HashArena {
data: FnvIndexSet::default(),
}
}

pub fn alloc(&mut self, value: T) -> Id<T> {
let (raw, _) = self.data.insert_full(value);
Id::from(raw as u32)
}
}

impl<T: Hash + Eq> Index<Id<T>> for HashArena<T> {
type Output = T;
fn index(&self, id: Id<T>) -> &T {
&self.data[id.raw as usize]
}
}
66 changes: 35 additions & 31 deletions src/internal/core.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,19 +7,19 @@ use std::collections::HashSet as Set;
use std::sync::Arc;

use crate::internal::{
Arena, DecisionLevel, IncompDpId, Incompatibility, PartialSolution, Relation, SatisfierSearch,
SmallVec,
Arena, DecisionLevel, HashArena, Id, IncompDpId, Incompatibility, PartialSolution, Relation,
SatisfierSearch, SmallVec,
};
use crate::{DependencyProvider, DerivationTree, Map, NoSolutionError, VersionSet};

/// Current state of the PubGrub algorithm.
#[derive(Clone)]
pub(crate) struct State<DP: DependencyProvider> {
root_package: DP::P,
pub root_package: Id<DP::P>,
root_version: DP::V,

#[allow(clippy::type_complexity)]
incompatibilities: Map<DP::P, Vec<IncompDpId<DP>>>,
incompatibilities: Map<Id<DP::P>, Vec<IncompDpId<DP>>>,

/// Store the ids of incompatibilities that are already contradicted.
/// For each one keep track of the decision level when it was found to be contradicted.
Expand All @@ -29,7 +29,7 @@ pub(crate) struct State<DP: DependencyProvider> {
/// All incompatibilities expressing dependencies,
/// with common dependents merged.
#[allow(clippy::type_complexity)]
merged_dependencies: Map<(DP::P, DP::P), SmallVec<IncompDpId<DP>>>,
merged_dependencies: Map<(Id<DP::P>, Id<DP::P>), SmallVec<IncompDpId<DP>>>,

/// Partial solution.
/// TODO: remove pub.
Expand All @@ -38,29 +38,35 @@ pub(crate) struct State<DP: DependencyProvider> {
/// The store is the reference storage for all incompatibilities.
pub(crate) incompatibility_store: Arena<Incompatibility<DP::P, DP::VS, DP::M>>,

/// The store is the reference storage for all packages.
pub(crate) package_store: HashArena<DP::P>,

/// This is a stack of work to be done in `unit_propagation`.
/// It can definitely be a local variable to that method, but
/// this way we can reuse the same allocation for better performance.
unit_propagation_buffer: SmallVec<DP::P>,
unit_propagation_buffer: SmallVec<Id<DP::P>>,
}

impl<DP: DependencyProvider> State<DP> {
/// Initialization of PubGrub state.
pub(crate) fn init(root_package: DP::P, root_version: DP::V) -> Self {
let mut incompatibility_store = Arena::new();
let mut package_store = HashArena::new();
let root_package = package_store.alloc(root_package);
let not_root_id = incompatibility_store.alloc(Incompatibility::not_root(
root_package.clone(),
root_package,
root_version.clone(),
));
let mut incompatibilities = Map::default();
incompatibilities.insert(root_package.clone(), vec![not_root_id]);
incompatibilities.insert(root_package, vec![not_root_id]);
Self {
root_package,
root_version,
incompatibilities,
contradicted_incompatibilities: Map::default(),
partial_solution: PartialSolution::empty(),
incompatibility_store,
package_store,
unit_propagation_buffer: SmallVec::Empty,
merged_dependencies: Map::default(),
}
Expand All @@ -75,18 +81,19 @@ impl<DP: DependencyProvider> State<DP> {
/// Add an incompatibility to the state.
pub(crate) fn add_incompatibility_from_dependencies(
&mut self,
package: DP::P,
package: Id<DP::P>,
version: DP::V,
deps: impl IntoIterator<Item = (DP::P, DP::VS)>,
) -> std::ops::Range<IncompDpId<DP>> {
// Create incompatibilities and allocate them in the store.
let new_incompats_id_range =
self.incompatibility_store
.alloc_iter(deps.into_iter().map(|dep| {
.alloc_iter(deps.into_iter().map(|(dep_p, dep_vs)| {
let dep_pid = self.package_store.alloc(dep_p);
Incompatibility::from_dependency(
package.clone(),
package,
<DP::VS as VersionSet>::singleton(version.clone()),
dep,
(dep_pid, dep_vs),
)
}));
// Merge the newly created incompatibilities with the older ones.
Expand All @@ -98,7 +105,10 @@ impl<DP: DependencyProvider> State<DP> {

/// Unit propagation is the core mechanism of the solving algorithm.
/// CF <https://github.com/dart-lang/pub/blob/master/doc/solver.md#unit-propagation>
pub(crate) fn unit_propagation(&mut self, package: DP::P) -> Result<(), NoSolutionError<DP>> {
pub(crate) fn unit_propagation(
&mut self,
package: Id<DP::P>,
) -> Result<(), NoSolutionError<DP>> {
self.unit_propagation_buffer.clear();
self.unit_propagation_buffer.push(package);
while let Some(current_package) = self.unit_propagation_buffer.pop() {
Expand All @@ -120,7 +130,7 @@ impl<DP: DependencyProvider> State<DP> {
Relation::Satisfied => {
log::info!(
"Start conflict resolution because incompat satisfied:\n {}",
current_incompat
current_incompat.display(&self.package_store)
);
conflict_id = Some(incompat_id);
break;
Expand All @@ -131,7 +141,7 @@ impl<DP: DependencyProvider> State<DP> {
// but so does allocating a hash map and hashing each item.
// In practice `unit_propagation_buffer` is small enough that we can just do a linear scan.
if !self.unit_propagation_buffer.contains(&package_almost) {
self.unit_propagation_buffer.push(package_almost.clone());
self.unit_propagation_buffer.push(package_almost);
}
// Add (not term) to the partial solution with incompat as cause.
self.partial_solution.add_derivation(
Expand All @@ -157,7 +167,7 @@ impl<DP: DependencyProvider> State<DP> {
self.build_derivation_tree(terminal_incompat_id)
})?;
self.unit_propagation_buffer.clear();
self.unit_propagation_buffer.push(package_almost.clone());
self.unit_propagation_buffer.push(package_almost);
// Add to the partial solution with incompat as cause.
self.partial_solution.add_derivation(
package_almost,
Expand All @@ -180,12 +190,12 @@ impl<DP: DependencyProvider> State<DP> {
fn conflict_resolution(
&mut self,
incompatibility: IncompDpId<DP>,
) -> Result<(DP::P, IncompDpId<DP>), IncompDpId<DP>> {
) -> Result<(Id<DP::P>, IncompDpId<DP>), IncompDpId<DP>> {
let mut current_incompat_id = incompatibility;
let mut current_incompat_changed = false;
loop {
if self.incompatibility_store[current_incompat_id]
.is_terminal(&self.root_package, &self.root_version)
.is_terminal(self.root_package, &self.root_version)
{
return Err(current_incompat_id);
} else {
Expand All @@ -197,7 +207,6 @@ impl<DP: DependencyProvider> State<DP> {
SatisfierSearch::DifferentDecisionLevels {
previous_satisfier_level,
} => {
let package = package.clone();
self.backtrack(
current_incompat_id,
current_incompat_changed,
Expand All @@ -213,7 +222,7 @@ impl<DP: DependencyProvider> State<DP> {
package,
&self.incompatibility_store,
);
log::info!("prior cause: {}", prior_cause);
log::info!("prior cause: {}", prior_cause.display(&self.package_store));
current_incompat_id = self.incompatibility_store.alloc(prior_cause);
current_incompat_changed = true;
}
Expand Down Expand Up @@ -256,19 +265,16 @@ impl<DP: DependencyProvider> State<DP> {
fn merge_incompatibility(&mut self, mut id: IncompDpId<DP>) {
if let Some((p1, p2)) = self.incompatibility_store[id].as_dependency() {
// If we are a dependency, there's a good chance we can be merged with a previous dependency
let deps_lookup = self
.merged_dependencies
.entry((p1.clone(), p2.clone()))
.or_default();
let deps_lookup = self.merged_dependencies.entry((p1, p2)).or_default();
if let Some((past, merged)) = deps_lookup.as_mut_slice().iter_mut().find_map(|past| {
self.incompatibility_store[id]
.merge_dependents(&self.incompatibility_store[*past])
.map(|m| (past, m))
}) {
let new = self.incompatibility_store.alloc(merged);
for (pkg, _) in self.incompatibility_store[new].iter() {
for (&pkg, _) in self.incompatibility_store[new].iter() {
self.incompatibilities
.entry(pkg.clone())
.entry(pkg)
.or_default()
.retain(|id| id != past);
}
Expand All @@ -278,14 +284,11 @@ impl<DP: DependencyProvider> State<DP> {
deps_lookup.push(id);
}
}
for (pkg, term) in self.incompatibility_store[id].iter() {
for (&pkg, term) in self.incompatibility_store[id].iter() {
if cfg!(debug_assertions) {
assert_ne!(term, &crate::term::Term::any());
}
self.incompatibilities
.entry(pkg.clone())
.or_default()
.push(id);
self.incompatibilities.entry(pkg).or_default().push(id);
}
}

Expand Down Expand Up @@ -320,6 +323,7 @@ impl<DP: DependencyProvider> State<DP> {
id,
&shared_ids,
&self.incompatibility_store,
&self.package_store,
&precomputed,
);
precomputed.insert(id, Arc::new(tree));
Expand Down
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