https://github.com/schell/apecs
An asyncronous and pleasant entity-component system for Rust
https://github.com/schell/apecs
app-engine ecs game-development game-engine rust
Last synced: about 1 month ago
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An asyncronous and pleasant entity-component system for Rust
- Host: GitHub
- URL: https://github.com/schell/apecs
- Owner: schell
- Created: 2022-03-14T00:43:26.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2024-09-20T21:03:03.000Z (7 months ago)
- Last Synced: 2025-03-09T17:50:14.560Z (about 2 months ago)
- Topics: app-engine, ecs, game-development, game-engine, rust
- Language: Rust
- Homepage:
- Size: 639 KB
- Stars: 63
- Watchers: 4
- Forks: 3
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# apecs
**A**sync-friendly and **P**leasant **E**ntity **C**omponent **S**ystem
`apecs` is an entity-component system written in Rust that can share world resources with
futures run in any async runtime. This makes it great for general applications,
quick game prototypes, DIY engines and any simulation that has discrete steps in time.
## Why
Most ECS libraries (and game main-loops in general) are polling based.
This is great for certain tasks, but things get complicated when programming in the time domain.
Async / await is great for programming in the time domain without explicitly spawning new threads
or blocking, but it isn't supported by ECS libraries.
`apecs` was designed to to be an ECS that plays nice with async / await.
## What and How
At its core `apecs` is a library for sharing resources across disparate polling and async loops.
It uses derivable traits and channels to orchestrate systems' access to resources and uses rayon
(where available) for concurrency.
## Goals
* productivity
* flexibility
* observability
* very well rounded performance, competitive with inspirational ECS libraries
- like `specs`, `bevy_ecs`, `hecs`, `legion`, `shipyard`, `planck_ecs`
- backed by criterion benchmarks
## Features
Here is a quick table of features compared to other ECSs.
| Feature | apecs | bevy_ecs | hecs | legion | planck_ecs | shipyard | specs |
|-------------------|----------|----------|----------|----------|------------|----------|-----------|
| storage |archetypal| hybrid |archetypal|archetypal| separated | sparse | separated |
| system scheduling | ✔️ | ✔️ | | ✔️ | ✔️ | ✔️ | ✔️ |
| early exit systems| ✔️ | | | | | | |
| parallel systems | ✔️ | ✔️ | ✔️ | ✔️ | | ✔️ | ✔️ |
| change tracking | ✔️ | ✔️ | | kinda | | ✔️ | ✔️ |
| async support | ✔️ | | | | | | |
### Feature examples
- systems with early exit and failure
```rust
use apecs::*;
#[derive(Clone, Copy, Debug, Default, PartialEq)]
struct Number(u32);
fn demo_system(mut u32_number: ViewMut) -> Result<(), GraphError> {
u32_number.0 += 1;
if u32_number.0 == 3 {
end()
} else {
ok()
}
}
let mut world = World::default();
world.add_subgraph(graph!(demo_system));
world.run().unwrap();
assert_eq!(Number(3), *world.get_resource::().unwrap());
```
- async support
- futures visit world resources through `Facade` using a closure.
- resources are acquired without lifetimes
- plays well with any async runtime
```rust
use apecs::*;
#[derive(Clone, Copy, Debug, Default, PartialEq)]
struct Number(u32);
let mut world = World::default();
let mut facade = world.facade();
let task = smol::spawn(async move {
loop {
let i = facade
.visit(|mut u32_number: ViewMut| {
u32_number.0 += 1;
u32_number.0
})
.await
.unwrap();
if i > 5 {
break;
}
}
});
while !task.is_finished() {
world.tick().unwrap();
world.get_facade_schedule().unwrap().run().unwrap();
}
assert_eq!(Number(6), *world.get_resource::().unwrap());
```
- system data derive macros
```rust
use apecs::*;
#[derive(Edges)]
struct MyData {
entities: View,
u32_number: ViewMut,
}
let mut world = World::default();
world
.visit(|mut my_data: MyData| {
*my_data.u32_number = 1;
})
.unwrap();
```
- system scheduling
- compatible systems are placed in parallel batches (a batch is a group of systems
that can run in parallel, ie they don't have conflicting borrows)
- systems may depend on other systems running before or after
- barriers
```rust
use apecs::*;
fn one(mut u32_number: ViewMut) -> Result<(), GraphError> {
*u32_number += 1;
end()
}
fn two(mut u32_number: ViewMut) -> Result<(), GraphError> {
*u32_number += 1;
end()
}
fn exit_on_three(mut f32_number: ViewMut) -> Result<(), GraphError> {
*f32_number += 1.0;
if *f32_number == 3.0 {
end()
} else {
ok()
}
}
fn lastly((u32_number, f32_number): (View, View)) -> Result<(), GraphError> {
if *u32_number == 2 && *f32_number == 3.0 {
end()
} else {
ok()
}
}
let mut world = World::default();
world.add_subgraph(
graph!(
// one should run before two
one < two,
// exit_on_three has no dependencies
exit_on_three
)
// add a barrier
.with_barrier()
.with_subgraph(
// all systems after a barrier run after the systems before a barrier
graph!(lastly),
),
);
assert_eq!(
vec![vec!["exit_on_three", "one"], vec!["two"], vec!["lastly"]],
world.get_schedule_names()
);
world.tick().unwrap();
assert_eq!(
vec![vec!["exit_on_three"], vec!["lastly"]],
world.get_schedule_names()
);
world.tick().unwrap();
world.tick().unwrap();
assert!(world.get_schedule_names().is_empty());
```
- component storage
- optimized for space and iteration time as archetypes
- queries with "maybe" and "without" semantics
- queries can find a single entity without iteration or filtering
- add and modified time tracking
- parallel queries (inner parallelism)
```rust
use apecs::*;
// Make a type for tracking changes
#[derive(Default)]
struct MyTracker(u64);
fn create(mut entities: ViewMut) -> Result<(), GraphError> {
for mut entity in (0..100).map(|_| entities.create()) {
entity.insert_bundle((0.0f32, 0u32, format!("{}:0", entity.id())));
}
end()
}
fn progress(q_f32s: Query<&mut f32>) -> Result<(), GraphError> {
for f32 in q_f32s.query().iter_mut() {
**f32 += 1.0;
}
ok()
}
fn sync(
(q_others, mut tracker): (Query<(&f32, &mut String, &mut u32)>, ViewMut),
) -> Result<(), GraphError> {
for (f32, string, u32) in q_others.query().iter_mut() {
if f32.was_modified_since(tracker.0) {
**u32 = **f32 as u32;
**string = format!("{}:{}", f32.id(), **u32);
}
}
tracker.0 = apecs::current_iteration();
ok()
}
// Entities and Components (which stores components) are default
// resources
let mut world = World::default();
world.add_subgraph(graph!(
create < progress < sync
));
assert_eq!(
vec![vec!["create"], vec!["progress"], vec!["sync"]],
world.get_schedule_names()
);
world.tick().unwrap(); // entities are created, components applied lazily
world.tick().unwrap(); // f32s are modified, u32s and strings are synced
world.tick().unwrap(); // f32s are modified, u32s and strings are synced
world
.visit(|q_bundle: Query<(&f32, &u32, &String)>| {
assert_eq!(
(2.0f32, 2u32, "13:2".to_string()),
q_bundle
.query()
.find_one(13)
.map(|(f, u, s)| (**f, **u, s.to_string()))
.unwrap()
);
})
.unwrap();
```
- outer parallelism (running systems in parallel)
- parallel system scheduling
- parallel execution of async futures
- parallelism is configurable (can be automatic or a requested number of threads, including 1)
```rust
use apecs::*;
#[derive(Default)]
struct F32(f32);
let mut world = World::default();
fn one(mut f32_number: ViewMut) -> Result<(), GraphError> {
f32_number.0 += 1.0;
ok()
}
fn two(f32_number: View) -> Result<(), GraphError> {
println!("system two reads {}", f32_number.0);
ok()
}
fn three(f32_number: View) -> Result<(), GraphError> {
println!("system three reads {}", f32_number.0);
ok()
}
world
.add_subgraph(graph!(one, two, three))
.with_parallelism(Parallelism::Automatic);
world.tick().unwrap();
```
- fully compatible with WASM and runs in the browser
## Roadmap
- your ideas go here
## Tests
```bash
cargo test
wasm-pack test --firefox crates/apecs
```
I like firefox, but you can use different browsers for the wasm tests. The tests
make sure apecs works on wasm.
## Benchmarks
The `apecs` benchmarks measure itself against my favorite ECS libs:
`specs`, `bevy`, `hecs`, `legion`, `shipyard` and `planck_ecs`.
```bash
cargo bench -p benchmarks
```
# Minimum supported Rust version 1.65
`apecs` uses generic associated types for its component iteration traits.