bevy_ecs/schedule/executor/
simple.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
#[cfg(feature = "trace")]
use bevy_utils::tracing::info_span;
use fixedbitset::FixedBitSet;
use std::panic::AssertUnwindSafe;

use crate::{
    schedule::{
        executor::is_apply_deferred, BoxedCondition, ExecutorKind, SystemExecutor, SystemSchedule,
    },
    world::World,
};

use super::__rust_begin_short_backtrace;

/// A variant of [`SingleThreadedExecutor`](crate::schedule::SingleThreadedExecutor) that calls
/// [`apply_deferred`](crate::system::System::apply_deferred) immediately after running each system.
#[derive(Default)]
pub struct SimpleExecutor {
    /// Systems sets whose conditions have been evaluated.
    evaluated_sets: FixedBitSet,
    /// Systems that have run or been skipped.
    completed_systems: FixedBitSet,
}

impl SystemExecutor for SimpleExecutor {
    fn kind(&self) -> ExecutorKind {
        ExecutorKind::Simple
    }

    fn init(&mut self, schedule: &SystemSchedule) {
        let sys_count = schedule.system_ids.len();
        let set_count = schedule.set_ids.len();
        self.evaluated_sets = FixedBitSet::with_capacity(set_count);
        self.completed_systems = FixedBitSet::with_capacity(sys_count);
    }

    fn run(
        &mut self,
        schedule: &mut SystemSchedule,
        world: &mut World,
        _skip_systems: Option<&FixedBitSet>,
    ) {
        // If stepping is enabled, make sure we skip those systems that should
        // not be run.
        #[cfg(feature = "bevy_debug_stepping")]
        if let Some(skipped_systems) = _skip_systems {
            // mark skipped systems as completed
            self.completed_systems |= skipped_systems;
        }

        for system_index in 0..schedule.systems.len() {
            #[cfg(feature = "trace")]
            let name = schedule.systems[system_index].name();
            #[cfg(feature = "trace")]
            let should_run_span = info_span!("check_conditions", name = &*name).entered();

            let mut should_run = !self.completed_systems.contains(system_index);
            for set_idx in schedule.sets_with_conditions_of_systems[system_index].ones() {
                if self.evaluated_sets.contains(set_idx) {
                    continue;
                }

                // evaluate system set's conditions
                let set_conditions_met =
                    evaluate_and_fold_conditions(&mut schedule.set_conditions[set_idx], world);

                if !set_conditions_met {
                    self.completed_systems
                        .union_with(&schedule.systems_in_sets_with_conditions[set_idx]);
                }

                should_run &= set_conditions_met;
                self.evaluated_sets.insert(set_idx);
            }

            // evaluate system's conditions
            let system_conditions_met =
                evaluate_and_fold_conditions(&mut schedule.system_conditions[system_index], world);

            should_run &= system_conditions_met;

            #[cfg(feature = "trace")]
            should_run_span.exit();

            // system has either been skipped or will run
            self.completed_systems.insert(system_index);

            if !should_run {
                continue;
            }

            let system = &mut schedule.systems[system_index];
            if is_apply_deferred(system) {
                continue;
            }

            let res = std::panic::catch_unwind(AssertUnwindSafe(|| {
                __rust_begin_short_backtrace::run(&mut **system, world);
            }));
            if let Err(payload) = res {
                eprintln!("Encountered a panic in system `{}`!", &*system.name());
                std::panic::resume_unwind(payload);
            }
        }

        self.evaluated_sets.clear();
        self.completed_systems.clear();
    }

    fn set_apply_final_deferred(&mut self, _: bool) {
        // do nothing. simple executor does not do a final sync
    }
}

impl SimpleExecutor {
    /// Creates a new simple executor for use in a [`Schedule`](crate::schedule::Schedule).
    /// This calls each system in order and immediately calls [`System::apply_deferred`](crate::system::System::apply_deferred).
    pub const fn new() -> Self {
        Self {
            evaluated_sets: FixedBitSet::new(),
            completed_systems: FixedBitSet::new(),
        }
    }
}

fn evaluate_and_fold_conditions(conditions: &mut [BoxedCondition], world: &mut World) -> bool {
    // not short-circuiting is intentional
    #[allow(clippy::unnecessary_fold)]
    conditions
        .iter_mut()
        .map(|condition| __rust_begin_short_backtrace::readonly_run(&mut **condition, world))
        .fold(true, |acc, res| acc && res)
}

#[cfg(test)]
#[test]
fn skip_automatic_sync_points() {
    // Schedules automatically insert apply_deferred systems, but these should
    // not be executed as they only serve as markers and are not initialized
    use crate::prelude::*;
    let mut sched = Schedule::default();
    sched.set_executor_kind(ExecutorKind::Simple);
    sched.add_systems((|_: Commands| (), || ()).chain());
    let mut world = World::new();
    sched.run(&mut world);
}