Move EntityList and SparseMap into the entity module.
These data structures are dependent on EntityRef and EntityMap, so it makes sense to keep them in the same module.
This commit is contained in:
Jakob Stoklund Olesen
347
lib/cretonne/src/entity/sparse.rs
Normal file
347
lib/cretonne/src/entity/sparse.rs
Normal file
@@ -0,0 +1,347 @@
|
||||
//! Sparse mapping of entity references to larger value types.
|
||||
//!
|
||||
//! This module provides a `SparseMap` data structure which implements a sparse mapping from an
|
||||
//! `EntityRef` key to a value type that may be on the larger side. This implementation is based on
|
||||
//! the paper:
|
||||
//!
|
||||
//! > Briggs, Torczon, *An efficient representation for sparse sets*,
|
||||
//! ACM Letters on Programming Languages and Systems, Volume 2, Issue 1-4, March-Dec. 1993.
|
||||
//!
|
||||
//! A `SparseMap<K, V>` map provides:
|
||||
//!
|
||||
//! - Memory usage equivalent to `EntityMap<K, u32>` + `Vec<V>`, so much smaller than
|
||||
//! `EntityMap<K, V>` for sparse mappings of larger `V` types.
|
||||
//! - Constant time lookup, slightly slower than `EntityMap`.
|
||||
//! - A very fast, constant time `clear()` operation.
|
||||
//! - Fast insert and erase operations.
|
||||
//! - Stable iteration that is as fast as a `Vec<V>`.
|
||||
//!
|
||||
//! # Compared to `EntityMap`
|
||||
//!
|
||||
//! When should we use a `SparseMap` instead of a secondary `EntityMap`? First of all, `SparseMap`
|
||||
//! does not provide the functionality of a primary `EntityMap` which can allocate and assign
|
||||
//! entity references to objects as they are pushed onto the map. It is only the secondary
|
||||
//! entity maps that can be replaced with a `SparseMap`.
|
||||
//!
|
||||
//! - A secondary entity map requires its values to implement `Default`, and it is a bit loose
|
||||
//! about creating new mappings to the default value. It doesn't distinguish clearly between an
|
||||
//! unmapped key and one that maps to the default value. `SparseMap` does not require `Default`
|
||||
//! values, and it tracks accurately if a key has been mapped or not.
|
||||
//! - Iterating over the contents of an `EntityMap` is linear in the size of the *key space*, while
|
||||
//! iterating over a `SparseMap` is linear in the number of elements in the mapping. This is an
|
||||
//! advantage precisely when the mapping is sparse.
|
||||
//! - `SparseMap::clear()` is constant time and super-fast. `EntityMap::clear()` is linear in the
|
||||
//! size of the key space. (Or, rather the required `resize()` call following the `clear()` is).
|
||||
//! - `SparseMap` requires the values to implement `SparseMapValue<K>` which means that they must
|
||||
//! contain their own key.
|
||||
|
||||
use entity::{EntityRef, EntityMap};
|
||||
use std::mem;
|
||||
use std::slice;
|
||||
use std::u32;
|
||||
|
||||
/// Trait for extracting keys from values stored in a `SparseMap`.
|
||||
///
|
||||
/// All values stored in a `SparseMap` must keep track of their own key in the map and implement
|
||||
/// this trait to provide access to the key.
|
||||
pub trait SparseMapValue<K> {
|
||||
/// Get the key of this sparse map value. This key is not allowed to change while the value
|
||||
/// is a member of the map.
|
||||
fn key(&self) -> K;
|
||||
}
|
||||
|
||||
/// A sparse mapping of entity references.
|
||||
pub struct SparseMap<K, V>
|
||||
where K: EntityRef,
|
||||
V: SparseMapValue<K>
|
||||
{
|
||||
sparse: EntityMap<K, u32>,
|
||||
dense: Vec<V>,
|
||||
}
|
||||
|
||||
impl<K, V> SparseMap<K, V>
|
||||
where K: EntityRef,
|
||||
V: SparseMapValue<K>
|
||||
{
|
||||
/// Create a new empty mapping.
|
||||
pub fn new() -> Self {
|
||||
SparseMap {
|
||||
sparse: EntityMap::new(),
|
||||
dense: Vec::new(),
|
||||
}
|
||||
}
|
||||
|
||||
/// Returns the number of elements in the map.
|
||||
pub fn len(&self) -> usize {
|
||||
self.dense.len()
|
||||
}
|
||||
|
||||
/// Returns true is the map contains no elements.
|
||||
pub fn is_empty(&self) -> bool {
|
||||
self.dense.is_empty()
|
||||
}
|
||||
|
||||
/// Remove all elements from the mapping.
|
||||
pub fn clear(&mut self) {
|
||||
self.dense.clear();
|
||||
}
|
||||
|
||||
/// Returns a reference to the value corresponding to the key.
|
||||
pub fn get(&self, key: K) -> Option<&V> {
|
||||
if let Some(idx) = self.sparse.get(key).cloned() {
|
||||
if let Some(entry) = self.dense.get(idx as usize) {
|
||||
if entry.key() == key {
|
||||
return Some(entry);
|
||||
}
|
||||
}
|
||||
}
|
||||
None
|
||||
}
|
||||
|
||||
/// Returns a mutable reference to the value corresponding to the key.
|
||||
///
|
||||
/// Note that the returned value must not be mutated in a way that would change its key. This
|
||||
/// would invalidate the sparse set data structure.
|
||||
pub fn get_mut(&mut self, key: K) -> Option<&mut V> {
|
||||
if let Some(idx) = self.sparse.get(key).cloned() {
|
||||
if let Some(entry) = self.dense.get_mut(idx as usize) {
|
||||
if entry.key() == key {
|
||||
return Some(entry);
|
||||
}
|
||||
}
|
||||
}
|
||||
None
|
||||
}
|
||||
|
||||
/// Return the index into `dense` of the value corresponding to `key`.
|
||||
fn index(&self, key: K) -> Option<usize> {
|
||||
if let Some(idx) = self.sparse.get(key).cloned() {
|
||||
let idx = idx as usize;
|
||||
if let Some(entry) = self.dense.get(idx) {
|
||||
if entry.key() == key {
|
||||
return Some(idx);
|
||||
}
|
||||
}
|
||||
}
|
||||
None
|
||||
}
|
||||
|
||||
/// Return `true` if the map contains a value corresponding to `key`.
|
||||
pub fn contains_key(&self, key: K) -> bool {
|
||||
self.get(key).is_some()
|
||||
}
|
||||
|
||||
/// Insert a value into the map.
|
||||
///
|
||||
/// If the map did not have this key present, `None` is returned.
|
||||
///
|
||||
/// If the map did have this key present, the value is updated, and the old value is returned.
|
||||
///
|
||||
/// It is not necessary to provide a key since the value knows its own key already.
|
||||
pub fn insert(&mut self, value: V) -> Option<V> {
|
||||
let key = value.key();
|
||||
|
||||
// Replace the existing entry for `key` if there is one.
|
||||
if let Some(entry) = self.get_mut(key) {
|
||||
return Some(mem::replace(entry, value));
|
||||
}
|
||||
|
||||
// There was no previous entry for `key`. Add it to the end of `dense`.
|
||||
let idx = self.dense.len();
|
||||
assert!(idx <= u32::MAX as usize, "SparseMap overflow");
|
||||
self.dense.push(value);
|
||||
self.sparse[key] = idx as u32;
|
||||
None
|
||||
}
|
||||
|
||||
/// Remove a value from the map and return it.
|
||||
pub fn remove(&mut self, key: K) -> Option<V> {
|
||||
if let Some(idx) = self.index(key) {
|
||||
let back = self.dense.pop().unwrap();
|
||||
|
||||
// Are we popping the back of `dense`?
|
||||
if idx == self.dense.len() {
|
||||
return Some(back);
|
||||
}
|
||||
|
||||
// We're removing an element from the middle of `dense`.
|
||||
// Replace the element at `idx` with the back of `dense`.
|
||||
// Repair `sparse` first.
|
||||
self.sparse[back.key()] = idx as u32;
|
||||
return Some(mem::replace(&mut self.dense[idx], back));
|
||||
}
|
||||
|
||||
// Nothing to remove.
|
||||
None
|
||||
}
|
||||
|
||||
/// Get an iterator over the values in the map.
|
||||
///
|
||||
/// The iteration order is entirely determined by the preceding sequence of `insert` and
|
||||
/// `remove` operations. In particular, if no elements were removed, this is the insertion
|
||||
/// order.
|
||||
pub fn values(&self) -> slice::Iter<V> {
|
||||
self.dense.iter()
|
||||
}
|
||||
|
||||
/// Get the values as a slice.
|
||||
pub fn as_slice(&self) -> &[V] {
|
||||
self.dense.as_slice()
|
||||
}
|
||||
}
|
||||
|
||||
/// Iterating over the elements of a set.
|
||||
impl<'a, K, V> IntoIterator for &'a SparseMap<K, V>
|
||||
where K: EntityRef,
|
||||
V: SparseMapValue<K>
|
||||
{
|
||||
type Item = &'a V;
|
||||
type IntoIter = slice::Iter<'a, V>;
|
||||
|
||||
fn into_iter(self) -> Self::IntoIter {
|
||||
self.values()
|
||||
}
|
||||
}
|
||||
|
||||
/// Any `EntityRef` can be used as a sparse map value representing itself.
|
||||
impl<T> SparseMapValue<T> for T
|
||||
where T: EntityRef
|
||||
{
|
||||
fn key(&self) -> T {
|
||||
*self
|
||||
}
|
||||
}
|
||||
|
||||
/// A sparse set of entity references.
|
||||
///
|
||||
/// Any type that implements `EntityRef` can be used as a sparse set value too.
|
||||
pub type SparseSet<T> = SparseMap<T, T>;
|
||||
|
||||
#[cfg(test)]
|
||||
mod tests {
|
||||
use super::*;
|
||||
use entity::EntityRef;
|
||||
use ir::Inst;
|
||||
|
||||
// Mock key-value object for testing.
|
||||
#[derive(PartialEq, Eq, Debug)]
|
||||
struct Obj(Inst, &'static str);
|
||||
|
||||
impl SparseMapValue<Inst> for Obj {
|
||||
fn key(&self) -> Inst {
|
||||
self.0
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn empty_immutable_map() {
|
||||
let i1 = Inst::new(1);
|
||||
let map: SparseMap<Inst, Obj> = SparseMap::new();
|
||||
|
||||
assert!(map.is_empty());
|
||||
assert_eq!(map.len(), 0);
|
||||
assert_eq!(map.get(i1), None);
|
||||
assert_eq!(map.values().count(), 0);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn single_entry() {
|
||||
let i0 = Inst::new(0);
|
||||
let i1 = Inst::new(1);
|
||||
let i2 = Inst::new(2);
|
||||
let mut map = SparseMap::new();
|
||||
|
||||
assert!(map.is_empty());
|
||||
assert_eq!(map.len(), 0);
|
||||
assert_eq!(map.get(i1), None);
|
||||
assert_eq!(map.get_mut(i1), None);
|
||||
assert_eq!(map.remove(i1), None);
|
||||
|
||||
assert_eq!(map.insert(Obj(i1, "hi")), None);
|
||||
assert!(!map.is_empty());
|
||||
assert_eq!(map.len(), 1);
|
||||
assert_eq!(map.get(i0), None);
|
||||
assert_eq!(map.get(i1), Some(&Obj(i1, "hi")));
|
||||
assert_eq!(map.get(i2), None);
|
||||
assert_eq!(map.get_mut(i0), None);
|
||||
assert_eq!(map.get_mut(i1), Some(&mut Obj(i1, "hi")));
|
||||
assert_eq!(map.get_mut(i2), None);
|
||||
|
||||
assert_eq!(map.remove(i0), None);
|
||||
assert_eq!(map.remove(i2), None);
|
||||
assert_eq!(map.remove(i1), Some(Obj(i1, "hi")));
|
||||
assert_eq!(map.len(), 0);
|
||||
assert_eq!(map.get(i1), None);
|
||||
assert_eq!(map.get_mut(i1), None);
|
||||
assert_eq!(map.remove(i0), None);
|
||||
assert_eq!(map.remove(i1), None);
|
||||
assert_eq!(map.remove(i2), None);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn multiple_entries() {
|
||||
let i0 = Inst::new(0);
|
||||
let i1 = Inst::new(1);
|
||||
let i2 = Inst::new(2);
|
||||
let i3 = Inst::new(3);
|
||||
let mut map = SparseMap::new();
|
||||
|
||||
assert_eq!(map.insert(Obj(i2, "foo")), None);
|
||||
assert_eq!(map.insert(Obj(i1, "bar")), None);
|
||||
assert_eq!(map.insert(Obj(i0, "baz")), None);
|
||||
|
||||
// Iteration order = insertion order when nothing has been removed yet.
|
||||
assert_eq!(map.values().map(|obj| obj.1).collect::<Vec<_>>(),
|
||||
["foo", "bar", "baz"]);
|
||||
|
||||
assert_eq!(map.len(), 3);
|
||||
assert_eq!(map.get(i0), Some(&Obj(i0, "baz")));
|
||||
assert_eq!(map.get(i1), Some(&Obj(i1, "bar")));
|
||||
assert_eq!(map.get(i2), Some(&Obj(i2, "foo")));
|
||||
assert_eq!(map.get(i3), None);
|
||||
|
||||
// Remove front object, causing back to be swapped down.
|
||||
assert_eq!(map.remove(i1), Some(Obj(i1, "bar")));
|
||||
assert_eq!(map.len(), 2);
|
||||
assert_eq!(map.get(i0), Some(&Obj(i0, "baz")));
|
||||
assert_eq!(map.get(i1), None);
|
||||
assert_eq!(map.get(i2), Some(&Obj(i2, "foo")));
|
||||
assert_eq!(map.get(i3), None);
|
||||
|
||||
// Reinsert something at a previously used key.
|
||||
assert_eq!(map.insert(Obj(i1, "barbar")), None);
|
||||
assert_eq!(map.len(), 3);
|
||||
assert_eq!(map.get(i0), Some(&Obj(i0, "baz")));
|
||||
assert_eq!(map.get(i1), Some(&Obj(i1, "barbar")));
|
||||
assert_eq!(map.get(i2), Some(&Obj(i2, "foo")));
|
||||
assert_eq!(map.get(i3), None);
|
||||
|
||||
// Replace an entry.
|
||||
assert_eq!(map.insert(Obj(i0, "bazbaz")), Some(Obj(i0, "baz")));
|
||||
assert_eq!(map.len(), 3);
|
||||
assert_eq!(map.get(i0), Some(&Obj(i0, "bazbaz")));
|
||||
assert_eq!(map.get(i1), Some(&Obj(i1, "barbar")));
|
||||
assert_eq!(map.get(i2), Some(&Obj(i2, "foo")));
|
||||
assert_eq!(map.get(i3), None);
|
||||
|
||||
// Check the reference `IntoIter` impl.
|
||||
let mut v = Vec::new();
|
||||
for i in &map {
|
||||
v.push(i.1);
|
||||
}
|
||||
assert_eq!(v.len(), map.len());
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn entity_set() {
|
||||
let i0 = Inst::new(0);
|
||||
let i1 = Inst::new(1);
|
||||
let mut set = SparseSet::new();
|
||||
|
||||
assert_eq!(set.insert(i0), None);
|
||||
assert_eq!(set.insert(i0), Some(i0));
|
||||
assert_eq!(set.insert(i1), None);
|
||||
assert_eq!(set.get(i0), Some(&i0));
|
||||
assert_eq!(set.get(i1), Some(&i1));
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user