[Merged by Bors] - Add Exponential Moving Average into diagnostics

crates/bevy_diagnostic/src/diagnostic.rs

@@ -37,6 +37,8 @@ pub struct Diagnostic {
  pub suffix: Cow<'static, str>,
  history: VecDeque<DiagnosticMeasurement>,
  sum: f64,
+ ema: f64,
+ ema_smoothing_factor: f64,
  max_history_length: usize,
  pub is_enabled: bool,
 }
@@ -45,6 +47,15 @@ impl Diagnostic {
  /// Add a new value as a [`DiagnosticMeasurement`]. Its timestamp will be [`Instant::now`].
  pub fn add_measurement(&mut self, value: f64) {
  let time = Instant::now();
+
+ if let Some(previous) = self.measurement() {
+ let delta = (time - previous.time).as_secs_f64();
+ let alpha = (delta / self.ema_smoothing_factor).clamp(0.0, 1.0);
+ self.ema += alpha * (value - self.ema);
+ } else {
+ self.ema = value;
+ }
+
  if self.max_history_length > 1 {
  if self.history.len() == self.max_history_length {
  if let Some(removed_diagnostic) = self.history.pop_front() {
@@ -57,6 +68,7 @@ impl Diagnostic {
  self.history.clear();
  self.sum = value;
  }
+
  self.history
  .push_back(DiagnosticMeasurement { time, value });
  }
@@ -83,6 +95,8 @@ impl Diagnostic {
  history: VecDeque::with_capacity(max_history_length),
  max_history_length,
  sum: 0.0,
+ ema: 0.0,
+ ema_smoothing_factor: 2.0 / 21.0,
  is_enabled: true,
  }
  }
@@ -94,6 +108,22 @@ impl Diagnostic {
  self
  }
 
+ /// The smoothing factor used for the exponential smoothing used for
+ /// [`smoothed`](Self::smoothed).
+ ///
+ /// If measurements come in less fequently than `smoothing_factor` seconds
+ /// apart, no smoothing will be applied. As measurements come in more
+ /// frequently, the smoothing takes a greater effect such that it takes
+ /// approximately `smoothing_factor` seconds for 83% of an instantaneous
+ /// change in measurement to e reflected in the smoothed value.
+ ///
+ /// A smoothing factor of 0.0 will effectively disable smoothing.
+ #[must_use]
+ pub fn with_smoothing_factor(mut self, smoothing_factor: f64) -> Self {
+ self.ema_smoothing_factor = smoothing_factor;
+ self
+ }
+
  /// Get the latest measurement from this diagnostic.
  #[inline]
  pub fn measurement(&self) -> Option<&DiagnosticMeasurement> {
@@ -105,7 +135,7 @@ impl Diagnostic {
  self.measurement().map(|measurement| measurement.value)
  }
 
- /// Return the mean (average) of this diagnostic's values.
+ /// Return the simple moving average of this diagnostic's recent values.
  /// N.B. this a cheap operation as the sum is cached.
  pub fn average(&self) -> Option<f64> {
  if !self.history.is_empty() {
@@ -115,6 +145,19 @@ impl Diagnostic {
  }
  }
 
+ /// Return the exponential moving average of this diagnostic.
+ ///
+ /// This is by default tuned to behave reasonably well for a typical
+ /// measurement that changes every frame such as frametime. This can be
+ /// adjusted using [`with_smoothing_factor`](Self::with_smoothing_factor).
+ pub fn smoothed(&self) -> Option<f64> {
+ if !self.history.is_empty() {
+ Some(self.ema)
+ } else {
+ None
+ }
+ }
+
  /// Return the number of elements for this diagnostic.
  pub fn history_len(&self) -> usize {
  self.history.len()

crates/bevy_diagnostic/src/frame_time_diagnostics_plugin.rs

@@ -25,7 +25,8 @@ impl FrameTimeDiagnosticsPlugin {
  pub fn setup_system(mut diagnostics: ResMut<Diagnostics>) {
  diagnostics.add(Diagnostic::new(Self::FRAME_TIME, "frame_time", 20).with_suffix("ms"));
  diagnostics.add(Diagnostic::new(Self::FPS, "fps", 20));
- diagnostics.add(Diagnostic::new(Self::FRAME_COUNT, "frame_count", 1));
+ diagnostics
+ .add(Diagnostic::new(Self::FRAME_COUNT, "frame_count", 1).with_smoothing_factor(0.0));
  }
 
  pub fn diagnostic_system(

crates/bevy_diagnostic/src/log_diagnostics_plugin.rs

@@ -53,16 +53,16 @@ impl LogDiagnosticsPlugin {
  }
 
  fn log_diagnostic(diagnostic: &Diagnostic) {
- if let Some(value) = diagnostic.value() {
+ if let Some(value) = diagnostic.smoothed() {
  if diagnostic.get_max_history_length() > 1 {
  if let Some(average) = diagnostic.average() {
  info!(
  target: "bevy diagnostic",
- // Suffix is only used for 's' as in seconds currently,
- // so we reserve one column for it; however,
- // Do not reserve one column for the suffix in the average
+ // Suffix is only used for 's' or 'ms' currently,
+ // so we reserve two columns for it; however,
+ // Do not reserve columns for the suffix in the average
  // The ) hugging the value is more aesthetically pleasing
- "{name:<name_width$}: {value:>11.6}{suffix:1} (avg {average:>.6}{suffix:})",
+ "{name:<name_width$}: {value:>11.6}{suffix:2} (avg {average:>.6}{suffix:})",
  name = diagnostic.name,
  suffix = diagnostic.suffix,
  name_width = crate::MAX_DIAGNOSTIC_NAME_WIDTH,

examples/stress_tests/bevymark.rs

@@ -96,35 +96,28 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
 
  let texture = asset_server.load("branding/icon.png");
 
+ let text_section = move |color, value: &str| {
+ TextSection::new(
+ value,
+ TextStyle {
+ font: asset_server.load("fonts/FiraSans-Bold.ttf"),
+ font_size: 40.0,
+ color,
+ },
+ )
+ };
+
  commands.spawn(Camera2dBundle::default());
  commands.spawn((
  TextBundle::from_sections([
- TextSection::new(
- "Bird Count: ",
- TextStyle {
- font: asset_server.load("fonts/FiraSans-Bold.ttf"),
- font_size: 40.0,
- color: Color::rgb(0.0, 1.0, 0.0),
- },
- ),
- TextSection::from_style(TextStyle {
- font: asset_server.load("fonts/FiraSans-Bold.ttf"),
- font_size: 40.0,
- color: Color::rgb(0.0, 1.0, 1.0),
- }),
- TextSection::new(
- "\nAverage FPS: ",
- TextStyle {
- font: asset_server.load("fonts/FiraSans-Bold.ttf"),
- font_size: 40.0,
- color: Color::rgb(0.0, 1.0, 0.0),
- },
- ),
- TextSection::from_style(TextStyle {
- font: asset_server.load("fonts/FiraSans-Bold.ttf"),
- font_size: 40.0,
- color: Color::rgb(0.0, 1.0, 1.0),
- }),
+ text_section(Color::GREEN, "Bird Count"),
+ text_section(Color::CYAN, ""),
+ text_section(Color::GREEN, "\nFPS (raw): "),
+ text_section(Color::CYAN, ""),
+ text_section(Color::GREEN, "\nFPS (SMA): "),
+ text_section(Color::CYAN, ""),
+ text_section(Color::GREEN, "\nFPS (EMA): "),
+ text_section(Color::CYAN, ""),
  ])
  .with_style(Style {
  position_type: PositionType::Absolute,
@@ -261,8 +254,14 @@ fn counter_system(
  }
 
  if let Some(fps) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
- if let Some(average) = fps.average() {
- text.sections[3].value = format!("{average:.2}");
+ if let Some(raw) = fps.value() {
+ text.sections[3].value = format!("{raw:.2}");
+ }
+ if let Some(sma) = fps.average() {
+ text.sections[5].value = format!("{sma:.2}");
+ }
+ if let Some(ema) = fps.smoothed() {
+ text.sections[7].value = format!("{ema:.2}");
  }
  };
 }

examples/ui/text.rs

@@ -93,9 +93,9 @@ fn text_color_system(time: Res<Time>, mut query: Query<&mut Text, With<ColorText
 fn text_update_system(diagnostics: Res<Diagnostics>, mut query: Query<&mut Text, With<FpsText>>) {
  for mut text in &mut query {
  if let Some(fps) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
- if let Some(average) = fps.average() {
+ if let Some(value) = fps.smoothed() {
  // Update the value of the second section
- text.sections[1].value = format!("{average:.2}");
+ text.sections[1].value = format!("{value:.2}");
  }
  }
  }

examples/ui/text_debug.rs

@@ -157,16 +157,16 @@ fn change_text_system(
  for mut text in &mut query {
  let mut fps = 0.0;
  if let Some(fps_diagnostic) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
- if let Some(fps_avg) = fps_diagnostic.average() {
- fps = fps_avg;
+ if let Some(fps_smoothed) = fps_diagnostic.smoothed() {
+ fps = fps_smoothed;
  }
  }
 
  let mut frame_time = time.delta_seconds_f64();
  if let Some(frame_time_diagnostic) = diagnostics.get(FrameTimeDiagnosticsPlugin::FRAME_TIME)
  {
- if let Some(frame_time_avg) = frame_time_diagnostic.average() {
- frame_time = frame_time_avg;
+ if let Some(frame_time_smoothed) = frame_time_diagnostic.smoothed() {
+ frame_time = frame_time_smoothed;
  }
  }