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Use u32 over usize for ComponentSparseSet indicies (#4723)

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# Objective
Use less memory to store SparseSet components.

## Solution
Change `ComponentSparseSet` to only use `Entity::id` in it's key internally, and change the usize value in it's SparseArray to use u32 instead, as it cannot have more than u32::MAX live entities stored at once.

This should reduce the overhead of storing components in sparse set storage by 50%.
This commit is contained in:
James Liu 2022-05-30 16:59:40 +00:00
parent c5e89894f4
commit 8e4e5a5634
1 changed files with 52 additions and 14 deletions
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66
crates/bevy_ecs/src/storage/sparse_set.rs
View file

@ -6,6 +6,8 @@ use crate::{
use bevy_ptr::{OwningPtr, Ptr};
use std::{cell::UnsafeCell, hash::Hash, marker::PhantomData};
type EntityId = u32;
#[derive(Debug)]
pub struct SparseArray<I, V = I> {
values: Vec<Option<V>>,
@ -96,8 +98,14 @@ impl<I: SparseSetIndex, V> SparseArray<I, V> {
pub struct ComponentSparseSet {
dense: BlobVec,
ticks: Vec<UnsafeCell<ComponentTicks>>,
// Internally this only relies on the Entity ID to keep track of where the component data is
// stored for entities that are alive. The generation is not required, but is stored
// in debug builds to validate that access is correct.
#[cfg(not(debug_assertions))]
entities: Vec<EntityId>,
#[cfg(debug_assertions)]
entities: Vec<Entity>,
sparse: SparseArray<Entity, usize>,
sparse: SparseArray<EntityId, u32>,
}
impl ComponentSparseSet {
@ -137,38 +145,55 @@ impl ComponentSparseSet {
/// The `value` pointer must point to a valid address that matches the [`Layout`](std::alloc::Layout)
/// inside the [`ComponentInfo`] given when constructing this sparse set.
pub unsafe fn insert(&mut self, entity: Entity, value: OwningPtr<'_>, change_tick: u32) {
if let Some(&dense_index) = self.sparse.get(entity) {
self.dense.replace_unchecked(dense_index, value);
*self.ticks.get_unchecked_mut(dense_index) =
if let Some(&dense_index) = self.sparse.get(entity.id()) {
debug_assert_eq!(entity, self.entities[dense_index as usize]);
let _entity = self.dense.replace_unchecked(dense_index as usize, value);
*self.ticks.get_unchecked_mut(dense_index as usize) =
UnsafeCell::new(ComponentTicks::new(change_tick));
} else {
let dense_index = self.dense.len();
self.dense.push(value);
self.sparse.insert(entity, dense_index);
self.sparse.insert(entity.id(), dense_index as u32);
debug_assert_eq!(self.ticks.len(), dense_index);
debug_assert_eq!(self.entities.len(), dense_index);
self.ticks
.push(UnsafeCell::new(ComponentTicks::new(change_tick)));
#[cfg(not(debug_assertions))]
self.entities.push(entity.id());
#[cfg(debug_assertions)]
self.entities.push(entity);
}
}
#[inline]
pub fn contains(&self, entity: Entity) -> bool {
self.sparse.contains(entity)
#[cfg(debug_assertions)]
{
if let Some(&dense_index) = self.sparse.get(entity.id()) {
debug_assert_eq!(entity, self.entities[dense_index as usize]);
true
} else {
false
}
}
#[cfg(not(debug_assertions))]
self.sparse.contains(entity.id())
}
#[inline]
pub fn get(&self, entity: Entity) -> Option<Ptr<'_>> {
self.sparse.get(entity).map(|dense_index| {
self.sparse.get(entity.id()).map(|dense_index| {
let dense_index = *dense_index as usize;
debug_assert_eq!(entity, self.entities[dense_index]);
// SAFE: if the sparse index points to something in the dense vec, it exists
unsafe { self.dense.get_unchecked(*dense_index) }
unsafe { self.dense.get_unchecked(dense_index) }
})
}
#[inline]
pub fn get_with_ticks(&self, entity: Entity) -> Option<(Ptr<'_>, &UnsafeCell<ComponentTicks>)> {
let dense_index = *self.sparse.get(entity)?;
let dense_index = *self.sparse.get(entity.id())? as usize;
debug_assert_eq!(entity, self.entities[dense_index]);
// SAFE: if the sparse index points to something in the dense vec, it exists
unsafe {
Some((
@ -180,7 +205,8 @@ impl ComponentSparseSet {
#[inline]
pub fn get_ticks(&self, entity: Entity) -> Option<&UnsafeCell<ComponentTicks>> {
let dense_index = *self.sparse.get(entity)?;
let dense_index = *self.sparse.get(entity.id())? as usize;
debug_assert_eq!(entity, self.entities[dense_index]);
// SAFE: if the sparse index points to something in the dense vec, it exists
unsafe { Some(self.ticks.get_unchecked(dense_index)) }
}
@ -189,7 +215,9 @@ impl ComponentSparseSet {
/// it exists).
#[must_use = "The returned pointer must be used to drop the removed component."]
pub fn remove_and_forget(&mut self, entity: Entity) -> Option<OwningPtr<'_>> {
self.sparse.remove(entity).map(|dense_index| {
self.sparse.remove(entity.id()).map(|dense_index| {
let dense_index = dense_index as usize;
debug_assert_eq!(entity, self.entities[dense_index]);
self.ticks.swap_remove(dense_index);
self.entities.swap_remove(dense_index);
let is_last = dense_index == self.dense.len() - 1;
@ -197,14 +225,20 @@ impl ComponentSparseSet {
let value = unsafe { self.dense.swap_remove_and_forget_unchecked(dense_index) };
if !is_last {
let swapped_entity = self.entities[dense_index];
*self.sparse.get_mut(swapped_entity).unwrap() = dense_index;
#[cfg(not(debug_assertions))]
let idx = swapped_entity;
#[cfg(debug_assertions)]
let idx = swapped_entity.id();
*self.sparse.get_mut(idx).unwrap() = dense_index as u32;
}
value
})
}
pub fn remove(&mut self, entity: Entity) -> bool {
if let Some(dense_index) = self.sparse.remove(entity) {
if let Some(dense_index) = self.sparse.remove(entity.id()) {
let dense_index = dense_index as usize;
debug_assert_eq!(entity, self.entities[dense_index]);
self.ticks.swap_remove(dense_index);
self.entities.swap_remove(dense_index);
let is_last = dense_index == self.dense.len() - 1;
@ -212,7 +246,11 @@ impl ComponentSparseSet {
unsafe { self.dense.swap_remove_and_drop_unchecked(dense_index) }
if !is_last {
let swapped_entity = self.entities[dense_index];
*self.sparse.get_mut(swapped_entity).unwrap() = dense_index;
#[cfg(not(debug_assertions))]
let idx = swapped_entity;
#[cfg(debug_assertions)]
let idx = swapped_entity.id();
*self.sparse.get_mut(idx).unwrap() = dense_index as u32;
}
true
} else {