Overhaul bezier curve benchmarks (bevyengine#17016)

# Objective

- Part of bevyengine#16647.
- The benchmarks for bezier curves have several issues and do not yet
use the new `bench!` naming scheme.

## Solution

- Make all `bevy_math` benchmarks use the `bench!` macro for their name.
- Delete the `build_accel_cubic()` benchmark, since it was an exact
duplicate of `build_pos_cubic()`.
- Remove `collect::<Vec<_>>()` call in `build_pos_cubic()` and replace
it with a `for` loop.
- Combine all of the benchmarks that measure `curve.position()` under a
single group, `curve_position`, and extract the common bench routine
into a helper function.
- Move the time calculation for the `curve.ease()` benchmark into the
setup closure so it is not tracked.
- Rename the benchmarks to be more descriptive on what they do.
  - `easing_1000` -> `segment_ease`
  - `cubic_position_Vec2` -> `curve_position/vec2`
  - `cubic_position_Vec3A` -> `curve_position/vec3a`
  - `cubic_position_Vec3` -> `curve_position/vec3`
  - `build_pos_cubic_100_points` -> `curve_iter_positions`

## Testing

- `cargo test -p benches --bench math`
- `cargo bench -p benches --bench math`
  - Then open `./target/criterion/report/index.html` to see the report!

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

benches/benches/bevy_math/bezier.rs

@@ -1,96 +1,99 @@
+use benches::bench;
+use bevy_math::{prelude::*, VectorSpace};
 use core::hint::black_box;
+use criterion::{
+    criterion_group, measurement::Measurement, BatchSize, BenchmarkGroup, BenchmarkId, Criterion,
+};
 
-use criterion::{criterion_group, Criterion};
+criterion_group!(benches, segment_ease, curve_position, curve_iter_positions);
 
-use bevy_math::prelude::*;
+fn segment_ease(c: &mut Criterion) {
+    let segment = black_box(CubicSegment::new_bezier(vec2(0.25, 0.1), vec2(0.25, 1.0)));
 
-fn easing(c: &mut Criterion) {
-    let cubic_bezier = CubicSegment::new_bezier(vec2(0.25, 0.1), vec2(0.25, 1.0));
-    c.bench_function("easing_1000", |b| {
-        b.iter(|| {
-            (0..1000).map(|i| i as f32 / 1000.0).for_each(|t| {
-                black_box(cubic_bezier.ease(black_box(t)));
-            });
-        });
+    c.bench_function(bench!("segment_ease"), |b| {
+        let mut t = 0;
+
+        b.iter_batched(
+            || {
+                // Increment `t` by 1, but use modulo to constrain it to `0..=1000`.
+                t = (t + 1) % 1001;
+
+                // Return time as a decimal between 0 and 1, inclusive.
+                t as f32 / 1000.0
+            },
+            |t| segment.ease(t),
+            BatchSize::SmallInput,
+        );
     });
 }
 
-fn cubic_2d(c: &mut Criterion) {
-    let bezier = CubicBezier::new([[
+fn curve_position(c: &mut Criterion) {
+    /// A helper function that benchmarks calling [`CubicCurve::position()`] over a generic [`VectorSpace`].
+    fn bench_curve<M: Measurement, P: VectorSpace>(
+        group: &mut BenchmarkGroup<M>,
+        name: &str,
+        curve: CubicCurve<P>,
+    ) {
+        group.bench_with_input(BenchmarkId::from_parameter(name), &curve, |b, curve| {
+            b.iter(|| curve.position(black_box(0.5)));
+        });
+    }
+
+    let mut group = c.benchmark_group(bench!("curve_position"));
+
+    let bezier_2 = CubicBezier::new([[
         vec2(0.0, 0.0),
         vec2(0.0, 1.0),
         vec2(1.0, 0.0),
         vec2(1.0, 1.0),
     ]])
     .to_curve()
-    .expect("Unable to build a curve from this data");
-    c.bench_function("cubic_position_Vec2", |b| {
-        b.iter(|| black_box(bezier.position(black_box(0.5))));
-    });
-}
+    .unwrap();
 
-fn cubic(c: &mut Criterion) {
-    let bezier = CubicBezier::new([[
-        vec3a(0.0, 0.0, 0.0),
-        vec3a(0.0, 1.0, 0.0),
-        vec3a(1.0, 0.0, 0.0),
-        vec3a(1.0, 1.0, 1.0),
-    ]])
-    .to_curve()
-    .expect("Unable to build a curve from this data");
-    c.bench_function("cubic_position_Vec3A", |b| {
-        b.iter(|| black_box(bezier.position(black_box(0.5))));
-    });
-}
+    bench_curve(&mut group, "vec2", bezier_2);
 
-fn cubic_vec3(c: &mut Criterion) {
-    let bezier = CubicBezier::new([[
+    let bezier_3 = CubicBezier::new([[
         vec3(0.0, 0.0, 0.0),
         vec3(0.0, 1.0, 0.0),
         vec3(1.0, 0.0, 0.0),
         vec3(1.0, 1.0, 1.0),
     ]])
     .to_curve()
-    .expect("Unable to build a curve from this data");
-    c.bench_function("cubic_position_Vec3", |b| {
-        b.iter(|| black_box(bezier.position(black_box(0.5))));
-    });
-}
+    .unwrap();
 
-fn build_pos_cubic(c: &mut Criterion) {
-    let bezier = CubicBezier::new([[
+    bench_curve(&mut group, "vec3", bezier_3);
+
+    let bezier_3a = CubicBezier::new([[
         vec3a(0.0, 0.0, 0.0),
         vec3a(0.0, 1.0, 0.0),
         vec3a(1.0, 0.0, 0.0),
         vec3a(1.0, 1.0, 1.0),
     ]])
     .to_curve()
-    .expect("Unable to build a curve from this data");
-    c.bench_function("build_pos_cubic_100_points", |b| {
-        b.iter(|| black_box(bezier.iter_positions(black_box(100)).collect::<Vec<_>>()));
-    });
+    .unwrap();
+
+    bench_curve(&mut group, "vec3a", bezier_3a);
+
+    group.finish();
 }
 
-fn build_accel_cubic(c: &mut Criterion) {
+fn curve_iter_positions(c: &mut Criterion) {
     let bezier = CubicBezier::new([[
         vec3a(0.0, 0.0, 0.0),
         vec3a(0.0, 1.0, 0.0),
         vec3a(1.0, 0.0, 0.0),
         vec3a(1.0, 1.0, 1.0),
     ]])
     .to_curve()
-    .expect("Unable to build a curve from this data");
-    c.bench_function("build_accel_cubic_100_points", |b| {
-        b.iter(|| black_box(bezier.iter_positions(black_box(100)).collect::<Vec<_>>()));
+    .unwrap();
+
+    c.bench_function(bench!("curve_iter_positions"), |b| {
+        b.iter(|| {
+            for x in bezier.iter_positions(black_box(100)) {
+                // Discard `x`, since we just care about `iter_positions()` being consumed, but make
+                // the compiler believe `x` is being used so it doesn't eliminate the iterator.
+                black_box(x);
+            }
+        });
     });
 }
-
-criterion_group!(
-    benches,
-    easing,
-    cubic_2d,
-    cubic_vec3,
-    cubic,
-    build_pos_cubic,
-    build_accel_cubic,
-);