d33f5c759c
# Objective Fixes #6689. ## Solution Add `single-threaded` as an optional non-default feature to `bevy_ecs` and `bevy_tasks` that: - disable the `ParallelExecutor` as a default runner - disables the multi-threaded `TaskPool` - internally replace `QueryParIter::for_each` calls with `Query::for_each`. Removed the `Mutex` and `Arc` usage in the single-threaded task pool.  ## Future Work/TODO Create type aliases for `Mutex`, `Arc` that change to single-threaaded equivalents where possible. --- ## Changelog Added: Optional default feature `multi-theaded` to that enables multithreaded parallelism in the engine. Disabling it disables all multithreading in exchange for higher single threaded performance. Does nothing on WASM targets. --------- Co-authored-by: Carter Anderson <mcanders1@gmail.com>
97 lines
3.9 KiB
Rust
97 lines
3.9 KiB
Rust
mod multi_threaded;
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mod simple;
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mod single_threaded;
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pub use self::multi_threaded::{MainThreadExecutor, MultiThreadedExecutor};
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pub use self::simple::SimpleExecutor;
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pub use self::single_threaded::SingleThreadedExecutor;
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use fixedbitset::FixedBitSet;
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use crate::{
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schedule::{BoxedCondition, NodeId},
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system::BoxedSystem,
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world::World,
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};
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/// Types that can run a [`SystemSchedule`] on a [`World`].
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pub(super) trait SystemExecutor: Send + Sync {
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fn kind(&self) -> ExecutorKind;
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fn init(&mut self, schedule: &SystemSchedule);
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fn run(&mut self, schedule: &mut SystemSchedule, world: &mut World);
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fn set_apply_final_deferred(&mut self, value: bool);
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}
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/// Specifies how a [`Schedule`](super::Schedule) will be run.
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///
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/// The default depends on the target platform:
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/// - [`SingleThreaded`](ExecutorKind::SingleThreaded) on WASM.
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/// - [`MultiThreaded`](ExecutorKind::MultiThreaded) everywhere else.
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#[derive(PartialEq, Eq, Default)]
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pub enum ExecutorKind {
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/// Runs the schedule using a single thread.
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///
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/// Useful if you're dealing with a single-threaded environment, saving your threads for
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/// other things, or just trying minimize overhead.
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#[cfg_attr(any(target_arch = "wasm32", not(feature = "multi-threaded")), default)]
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SingleThreaded,
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/// Like [`SingleThreaded`](ExecutorKind::SingleThreaded) but calls [`apply_deferred`](crate::system::System::apply_deferred)
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/// immediately after running each system.
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Simple,
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/// Runs the schedule using a thread pool. Non-conflicting systems can run in parallel.
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#[cfg_attr(all(not(target_arch = "wasm32"), feature = "multi-threaded"), default)]
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MultiThreaded,
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}
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/// Holds systems and conditions of a [`Schedule`](super::Schedule) sorted in topological order
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/// (along with dependency information for multi-threaded execution).
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///
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/// Since the arrays are sorted in the same order, elements are referenced by their index.
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/// [`FixedBitSet`] is used as a smaller, more efficient substitute of `HashSet<usize>`.
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#[derive(Default)]
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pub struct SystemSchedule {
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pub(super) systems: Vec<BoxedSystem>,
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pub(super) system_conditions: Vec<Vec<BoxedCondition>>,
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pub(super) set_conditions: Vec<Vec<BoxedCondition>>,
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pub(super) system_ids: Vec<NodeId>,
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pub(super) set_ids: Vec<NodeId>,
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pub(super) system_dependencies: Vec<usize>,
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pub(super) system_dependents: Vec<Vec<usize>>,
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pub(super) sets_with_conditions_of_systems: Vec<FixedBitSet>,
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pub(super) systems_in_sets_with_conditions: Vec<FixedBitSet>,
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}
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impl SystemSchedule {
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/// Creates an empty [`SystemSchedule`].
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pub const fn new() -> Self {
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Self {
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systems: Vec::new(),
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system_conditions: Vec::new(),
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set_conditions: Vec::new(),
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system_ids: Vec::new(),
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set_ids: Vec::new(),
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system_dependencies: Vec::new(),
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system_dependents: Vec::new(),
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sets_with_conditions_of_systems: Vec::new(),
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systems_in_sets_with_conditions: Vec::new(),
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}
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}
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}
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/// Instructs the executor to call [`System::apply_deferred`](crate::system::System::apply_deferred)
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/// on the systems that have run but not applied their [`Deferred`](crate::system::Deferred) system parameters (like [`Commands`](crate::prelude::Commands)) or other system buffers.
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///
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/// **Notes**
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/// - This function (currently) does nothing if it's called manually or wrapped inside a [`PipeSystem`](crate::system::PipeSystem).
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/// - Modifying a [`Schedule`](super::Schedule) may change the order buffers are applied.
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#[doc(alias = "apply_system_buffers")]
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#[allow(unused_variables)]
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pub fn apply_deferred(world: &mut World) {}
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/// Returns `true` if the [`System`](crate::system::System) is an instance of [`apply_deferred`].
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pub(super) fn is_apply_deferred(system: &BoxedSystem) -> bool {
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use std::any::Any;
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// deref to use `System::type_id` instead of `Any::type_id`
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system.as_ref().type_id() == apply_deferred.type_id()
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}
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