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use crate::{
dispatch::Dispatcher, world::ResourceId, Accessor, AccessorCow, DynamicSystemData, RunningTime,
System, SystemData, World,
};
/// The `BatchAccessor` is used to notify the main dispatcher of the read and
/// write resources of the `System`s contained in the batch ("sub systems").
#[derive(Debug)]
pub struct BatchAccessor {
reads: Vec<ResourceId>,
writes: Vec<ResourceId>,
}
impl BatchAccessor {
/// Creates a `BatchAccessor`
pub fn new(reads: Vec<ResourceId>, writes: Vec<ResourceId>) -> Self {
BatchAccessor { reads, writes }
}
}
impl Accessor for BatchAccessor {
fn try_new() -> Option<Self> {
None
}
fn reads(&self) -> Vec<ResourceId> {
self.reads.clone()
}
fn writes(&self) -> Vec<ResourceId> {
self.writes.clone()
}
}
/// The `BatchUncheckedWorld` wraps an instance of the world.
/// You have to specify this as `SystemData` for a `System` implementing
/// `BatchController`.
pub struct BatchUncheckedWorld<'a>(pub &'a World);
impl<'a> DynamicSystemData<'a> for BatchUncheckedWorld<'a> {
type Accessor = BatchAccessor;
fn setup(_accessor: &Self::Accessor, _world: &mut World) {}
fn fetch(_access: &Self::Accessor, world: &'a World) -> Self {
BatchUncheckedWorld(world)
}
}
/// The `BatchController` describes things that allow one to control how batches
/// of systems are executed.
///
/// A batch is a set of systems represented as a dispatcher (a sub-dispatcher,
/// if you like).
///
/// It is registered with [`add_batch`][crate::DispatcherBuilder::add_batch],
/// together with the corresponding sub-dispatcher.
///
/// See the
/// [batch_dispatching](https://github.com/amethyst/shred/blob/master/examples/batch_dispatching.rs)
/// example.
///
/// The [`MultiDispatcher`] may help with implementing this in most common
/// cases.
pub trait BatchController<'a, 'b, 'c> {
/// This associated type has to contain all resources batch controller uses
/// directly.
///
/// Note that these are not fetched automatically for the controller, as is
/// the case with ordinary [`System`]s. This is because the fetched
/// references might need to be dropped before actually dispatching the
/// other systems to avoid collisions on them and it would not
/// be possible to perform using a parameter.
///
/// Therefore, these are only *declared* here, but not automatically
/// fetched. If the declaration does not match reality, the scheduler
/// might make suboptimal decisions (if this declares more than is
/// actually needed) or it may panic in runtime (in case it declares less
/// and there happens to be a collision).
type BatchSystemData: SystemData<'c>;
/// The body of the controller.
///
/// It is allowed to fetch (manually) and examine its
/// [`BatchSystemData`][BatchController::BatchSystemData]. Then it shall
/// drop all fetched references and is free to call
/// `dispatcher.dispatch(world)` as many time as it sees fit.
fn run(&mut self, world: &'c World, dispatcher: &mut Dispatcher<'a, 'b>);
/// Estimate how heavy the whole controller, including the sub-systems, is
/// in terms of computation costs.
fn running_time(&self) -> RunningTime {
RunningTime::VeryLong
}
}
pub(crate) struct BatchControllerSystem<'a, 'b, C> {
accessor: BatchAccessor,
controller: C,
dispatcher: Dispatcher<'a, 'b>,
}
impl<'a, 'b, 'c, C> BatchControllerSystem<'a, 'b, C>
where
C: BatchController<'a, 'b, 'c>,
{
pub(crate) unsafe fn create(
accessor: BatchAccessor,
controller: C,
dispatcher: Dispatcher<'a, 'b>,
) -> Self {
Self {
accessor,
controller,
dispatcher,
}
}
}
impl<'a, 'b, 'c, C> System<'c> for BatchControllerSystem<'a, 'b, C>
where
C: BatchController<'a, 'b, 'c>,
{
type SystemData = BatchUncheckedWorld<'c>;
fn run(&mut self, data: Self::SystemData) {
self.controller.run(data.0, &mut self.dispatcher);
}
fn running_time(&self) -> RunningTime {
self.controller.running_time()
}
fn accessor<'s>(&'s self) -> AccessorCow<'c, 's, Self> {
AccessorCow::Ref(&self.accessor)
}
fn setup(&mut self, world: &mut World) {
world.setup::<C::BatchSystemData>();
self.dispatcher.setup(world);
}
}
unsafe impl<C: Send> Send for BatchControllerSystem<'_, '_, C> {}
unsafe impl<C: Sync> Sync for BatchControllerSystem<'_, '_, C> {}
/// The controlling parts of simplified [`BatchController`]s for running a batch
/// fixed number of times.
///
/// If one needs to implement a [`BatchController`] that first examines some
/// data and decides upfront how many times a set of sub-systems are to be
/// dispatched, this can help with the implementation. This is less flexible (it
/// can't examine things in-between iterations of dispatching, for example), but
/// is often enough and more convenient as it avoids manual fetching
/// of the resources.
///
/// A common example is pausing a game ‒ based on some resource, the game
/// physics systems are run either 0 times or once.
///
/// A bigger example can be found in the
/// [multi_batch_dispatching](https://github.com/amethyst/shred/blob/master/examples/multi_batch_dispatching.rs).
///
/// To be useful, pass the controller to the constructor of [`MultiDispatcher`]
/// and register with [`add_batch`][crate::DispatcherBuilder::add_batch].
pub trait MultiDispatchController<'a>: Send {
/// What data it needs to decide on how many times the subsystems should be
/// run.
///
/// This may overlap with system data used by the subsystems, but doesn't
/// have to contain them.
type SystemData: SystemData<'a>;
/// Performs the decision.
///
/// Returns the number of times the batch should be run and the
/// [`MultiDispatcher`] will handle the actual execution.
fn plan(&mut self, data: Self::SystemData) -> usize;
}
/// A bridge from [`MultiDispatchController`] to [`BatchController`].
///
/// This allows to turn a [`MultiDispatchController`] into a [`BatchController`]
/// so it can be registered with
/// [`add_batch`][crate::DispatcherBuilder::add_batch].
pub struct MultiDispatcher<C> {
controller: C,
}
impl<C> MultiDispatcher<C> {
/// Constructor.
///
/// The `controller` should implement [`MultiDispatchController`].
pub fn new(controller: C) -> Self {
Self { controller }
}
}
impl<'a, 'b, 'c, C> BatchController<'a, 'b, 'c> for MultiDispatcher<C>
where
C: MultiDispatchController<'c>,
{
type BatchSystemData = C::SystemData;
fn run(&mut self, world: &'c World, dispatcher: &mut Dispatcher<'a, 'b>) {
let n = {
let plan_data = world.system_data();
self.controller.plan(plan_data)
};
for _ in 0..n {
dispatcher.dispatch(world);
}
}
}
#[cfg(test)]
mod tests {
use crate::{BatchController, Dispatcher, DispatcherBuilder, System, World, Write};
/// This test demonstrate that the batch system is able to correctly setup
/// its resources to default datas.
#[test]
fn test_setup() {
let mut dispatcher = DispatcherBuilder::new()
.with_batch(
CustomBatchControllerSystem,
DispatcherBuilder::new()
.with(BuyTomatoSystem, "buy_tomato_system", &[])
.with(BuyPotatoSystem, "buy_potato_system", &[]),
"BatchSystemTest",
&[],
)
.build();
let mut world = World::empty();
dispatcher.setup(&mut world);
let potato_store = world.fetch::<PotatoStore>();
let tomato_store = world.fetch::<TomatoStore>();
assert!(!potato_store.is_store_open);
assert!(!tomato_store.is_store_open);
assert_eq!(potato_store.potato_count, 50);
assert_eq!(tomato_store.tomato_count, 50);
}
/// This test demonstrate that the `CustomBatchControllerSystem` is able to
/// dispatch its systems three times per dispatching in parallel.
///
/// The parallel dispatching happen because there is no dependency between
/// the two systems.
///
/// Also the `OpenStoresSystem' and the `CloseStoresSystem` which request
/// mutable access to the same dependencies used by the store systems
/// are dispatched in sequence; respectivelly before and after the
/// batch.
///
/// Note that the Setup of the dispatcher is able to correctly create the
/// store objects with default data.
#[test]
fn test_parallel_batch_execution() {
let mut dispatcher = DispatcherBuilder::new()
.with(OpenStoresSystem, "open_stores_system", &[])
.with_batch(
CustomBatchControllerSystem,
DispatcherBuilder::new()
.with(BuyTomatoSystem, "buy_tomato_system", &[])
.with(BuyPotatoSystem, "buy_potato_system", &[]),
"BatchSystemTest",
&[],
)
.with(CloseStoresSystem, "close_stores_system", &[])
.build();
let mut world = World::empty();
dispatcher.setup(&mut world);
{
// Initial assertion
let potato_store = world.fetch::<PotatoStore>();
let tomato_store = world.fetch::<TomatoStore>();
assert!(!potato_store.is_store_open);
assert!(!tomato_store.is_store_open);
assert_eq!(potato_store.potato_count, 50);
assert_eq!(tomato_store.tomato_count, 50);
}
// Running phase
for _i in 0..10 {
dispatcher.dispatch(&world);
}
{
// This demonstrate that the batch system dispatch three times per
// dispatch.
let potato_store = world.fetch::<PotatoStore>();
let tomato_store = world.fetch::<TomatoStore>();
assert!(!potato_store.is_store_open);
assert!(!tomato_store.is_store_open);
assert_eq!(potato_store.potato_count, 50 - (3 * 10));
assert_eq!(tomato_store.tomato_count, 50 - (3 * 10));
}
}
/// This test demonstrate that the `CustomBatchControllerSystem` is able to
/// dispatch its systems three times per dispatching in sequence.
///
/// The sequence dispatching happen because there is a dependency between
/// the two systems.
///
/// Also the `OpenStoresSystem' and the `CloseStoresSystem` which request
/// mutable access to the same dependencies used by the store systems
/// are dispatched in sequence; respectivelly before and after the
/// batch.
///
/// The Setup of the dispatcher is able to correctly create the
/// store objects with default data.
/// Note the CustomWallet is created by the Batch setup demonstrating once
/// again that it works.
#[test]
fn test_sequence_batch_execution() {
let mut dispatcher = DispatcherBuilder::new()
.with(OpenStoresSystem, "open_stores_system", &[])
.with_batch(
CustomBatchControllerSystem,
DispatcherBuilder::new()
.with(BuyTomatoWalletSystem, "buy_tomato_system", &[])
.with(BuyPotatoWalletSystem, "buy_potato_system", &[]),
"BatchSystemTest",
&[],
)
.with(CloseStoresSystem, "close_stores_system", &[])
.build();
let mut world = World::empty();
dispatcher.setup(&mut world);
{
// Initial assertion
let potato_store = world.fetch::<PotatoStore>();
let tomato_store = world.fetch::<TomatoStore>();
let customer_wallet = world.fetch::<CustomerWallet>();
assert!(!potato_store.is_store_open);
assert!(!tomato_store.is_store_open);
assert_eq!(potato_store.potato_count, 50);
assert_eq!(tomato_store.tomato_count, 50);
assert_eq!(customer_wallet.cents_count, 2000);
}
// Running phase
for _i in 0..10 {
dispatcher.dispatch(&world);
}
{
// This demonstrate that the batch system dispatch three times per
// dispatch.
let potato_store = world.fetch::<PotatoStore>();
let tomato_store = world.fetch::<TomatoStore>();
let customer_wallet = world.fetch::<CustomerWallet>();
assert!(!potato_store.is_store_open);
assert!(!tomato_store.is_store_open);
assert_eq!(potato_store.potato_count, 50 - (3 * 10));
assert_eq!(tomato_store.tomato_count, 50 - (3 * 10));
assert_eq!(customer_wallet.cents_count, 2000 - ((50 + 150) * 3 * 10));
}
}
// Resources
#[derive(Debug, Clone, Copy)]
pub struct PotatoStore {
pub is_store_open: bool,
pub potato_count: i32,
}
impl Default for PotatoStore {
fn default() -> Self {
PotatoStore {
is_store_open: false,
potato_count: 50,
}
}
}
#[derive(Debug, Clone, Copy)]
pub struct TomatoStore {
pub is_store_open: bool,
pub tomato_count: i32,
}
impl Default for TomatoStore {
fn default() -> Self {
TomatoStore {
is_store_open: false,
tomato_count: 50,
}
}
}
#[derive(Debug, Clone, Copy)]
pub struct CustomerWallet {
pub cents_count: i32,
}
impl Default for CustomerWallet {
fn default() -> Self {
CustomerWallet { cents_count: 2000 }
}
}
// Open / Close Systems
pub struct OpenStoresSystem;
impl<'a> System<'a> for OpenStoresSystem {
type SystemData = (Write<'a, PotatoStore>, Write<'a, TomatoStore>);
fn run(&mut self, mut data: Self::SystemData) {
data.0.is_store_open = true;
data.1.is_store_open = true;
}
}
pub struct CloseStoresSystem;
impl<'a> System<'a> for CloseStoresSystem {
type SystemData = (Write<'a, PotatoStore>, Write<'a, TomatoStore>);
fn run(&mut self, mut data: Self::SystemData) {
data.0.is_store_open = false;
data.1.is_store_open = false;
}
}
// Buy Systems
pub struct BuyPotatoSystem;
impl<'a> System<'a> for BuyPotatoSystem {
type SystemData = Write<'a, PotatoStore>;
fn run(&mut self, mut potato_store: Self::SystemData) {
assert!(potato_store.is_store_open);
potato_store.potato_count -= 1;
}
}
pub struct BuyTomatoSystem;
impl<'a> System<'a> for BuyTomatoSystem {
type SystemData = Write<'a, TomatoStore>;
fn run(&mut self, mut tomato_store: Self::SystemData) {
assert!(tomato_store.is_store_open);
tomato_store.tomato_count -= 1;
}
}
// Buy systems with wallet
pub struct BuyPotatoWalletSystem;
impl<'a> System<'a> for BuyPotatoWalletSystem {
type SystemData = (Write<'a, PotatoStore>, Write<'a, CustomerWallet>);
fn run(&mut self, (mut potato_store, mut customer_wallet): Self::SystemData) {
assert!(potato_store.is_store_open);
potato_store.potato_count -= 1;
customer_wallet.cents_count -= 50;
}
}
pub struct BuyTomatoWalletSystem;
impl<'a> System<'a> for BuyTomatoWalletSystem {
type SystemData = (Write<'a, TomatoStore>, Write<'a, CustomerWallet>);
fn run(&mut self, (mut tomato_store, mut customer_wallet): Self::SystemData) {
assert!(tomato_store.is_store_open);
tomato_store.tomato_count -= 1;
customer_wallet.cents_count -= 150;
}
}
// Custom Batch Controller which dispatch the systems three times
pub struct CustomBatchControllerSystem;
impl<'a, 'b> BatchController<'a, 'b, '_> for CustomBatchControllerSystem {
type BatchSystemData = ();
fn run(&mut self, world: &World, dispatcher: &mut Dispatcher<'a, 'b>) {
for _i in 0..3 {
dispatcher.dispatch(world);
}
}
}
}