feat: command benchmarks

Part of #12.

benches/ecs/commands.rs

@@ -0,0 +1,64 @@
+use super::types::*;
+use bevy::ecs::{prelude::*, world::CommandQueue};
+use criterion::Criterion;
+use std::{hint::black_box, iter::repeat};
+
+/// Benchmark that flushes an empty [`CommandQueue`], applying it to the world.
+pub fn empty_queue(c: &mut Criterion) {
+    c.bench_function("ecs::commands::apply_queue", |b| {
+        let mut world = World::new();
+        let mut queue = CommandQueue::default();
+
+        b.iter(move || {
+            queue.apply(&mut world);
+        });
+    });
+}
+
+/// Benchmark that pushes a command that does nothing to the queue, then applies it.
+pub fn nothing(c: &mut Criterion) {
+    fn nothing(_: &mut World) {}
+
+    c.bench_function("ecs::commands::empty", |b| {
+        let mut world = World::new();
+        let mut queue = CommandQueue::default();
+
+        b.iter(move || {
+            let mut commands = Commands::new(&mut queue, &world);
+            commands.push(black_box(nothing));
+            queue.apply(&mut world);
+        });
+    });
+}
+
+/// Benchmark that spawns an entity using [`Commands`].
+///
+/// This is meant to be compared with [`world::spawn`](super::world::spawn).
+pub fn spawn(c: &mut Criterion) {
+    c.bench_function("ecs::commands::spawn", |b| {
+        let mut world = World::new();
+        let mut queue = CommandQueue::default();
+
+        b.iter(move || {
+            let mut commands = Commands::new(&mut queue, &world);
+            commands.spawn((A(0), B(0)));
+            queue.apply(&mut world);
+        });
+    });
+}
+
+/// Benchamrks spawning a batch of entities using [`Commands`].
+///
+/// This is meant to be compared with [`world::spawn_batch`](super::world::spawn_batch).
+pub fn spawn_batch(c: &mut Criterion) {
+    c.bench_function("ecs::commands::spawn_batch", |b| {
+        let mut world = World::new();
+        let mut queue = CommandQueue::default();
+
+        b.iter(move || {
+            let mut commands = Commands::new(&mut queue, &world);
+            commands.spawn_batch(repeat((A(0), (B(0)))).take(50));
+            queue.apply(&mut world);
+        });
+    });
+}

benches/ecs/mod.rs

@@ -1,10 +1,15 @@
+mod commands;
 mod types;
 mod world;
 
 use criterion::criterion_group;
 
 criterion_group!(
     group,
+    commands::empty_queue,
+    commands::nothing,
+    commands::spawn,
+    commands::spawn_batch,
     world::spawn,
     world::spawn_batch,
     world::despawn,