[On-device adaptive brightness] Only adjust brightness after model is sufficiently trained

Adapter now keeps track of number of model iterations and only starts changing
brightness based on min_model_iteration_count.

Bug: 881215
Change-Id: Ie9dcf15090f2e808630ad82a2bd2cfebad7cf00a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1621477
Commit-Queue: Jia Meng <jiameng@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Michael Martis <martis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662908}

chrome/browser/chromeos/power/auto_screen_brightness/adapter.cc

@@ -208,6 +208,7 @@ void Adapter::OnUserBrightnessChangeRequested() {
     decision_at_first_recent_user_brightness_request_ =
         CanAdjustBrightness(now);
     first_recent_user_brightness_request_time_ = now;
+    model_iteration_count_at_user_brightness_change_ = model_.iteration_count;
   }
 
   if (params_.user_adjustment_effect != UserAdjustmentEffect::kContinueAuto) {
@@ -383,6 +384,15 @@ void Adapter::InitParams(const ModelConfig& model_config) {
   params_.user_adjustment_effect =
       static_cast<UserAdjustmentEffect>(user_adjustment_effect_as_int);
 
+  params_.min_model_iteration_count = base::GetFieldTrialParamByFeatureAsInt(
+      features::kAutoScreenBrightness, "min_model_iteration_count",
+      params_.min_model_iteration_count);
+  if (params_.min_model_iteration_count <= 0) {
+    LogParameterError(ParameterError::kAdapterError);
+    enabled_by_model_configs_ = false;
+    return;
+  }
+
   UMA_HISTOGRAM_ENUMERATION("AutoScreenBrightness.UserAdjustmentEffect",
                             params_.user_adjustment_effect);
 }
@@ -510,6 +520,13 @@ Adapter::AdapterDecision Adapter::CanAdjustBrightness(base::TimeTicks now) {
     return decision;
   }
 
+  if (params_.model_curve == ModelCurve::kPersonal &&
+      model_.iteration_count < params_.min_model_iteration_count) {
+    decision.no_brightness_change_cause =
+        NoBrightnessChangeCause::kWaitingForTrainedPersonalCurve;
+    return decision;
+  }
+
   // Wait until we've had enough ALS data to calc avg.
   if (now - als_init_time_ < params_.auto_brightness_als_horizon) {
     decision.no_brightness_change_cause =
@@ -603,6 +620,12 @@ void Adapter::AdjustBrightness(BrightnessChangeCause cause,
   UMA_HISTOGRAM_ENUMERATION("AutoScreenBrightness.BrightnessChange.Cause",
                             cause);
 
+  if (params_.model_curve == ModelCurve::kPersonal) {
+    UMA_HISTOGRAM_COUNTS_1000(
+        "AutoScreenBrightness.BrightnessChange.ModelIteration",
+        model_.iteration_count);
+  }
+
   WriteLogMessages(log_als_avg, brightness, cause);
   model_brightness_change_counter_++;
 
@@ -764,6 +787,13 @@ void Adapter::LogAdapterDecision(
     base::UmaHistogramCounts1000(histogram_prefix + "Unknown.AlsStd",
                                  logged_stddev);
   }
+
+  // Log model iteration count.
+  if (params_.model_curve == ModelCurve::kPersonal) {
+    base::UmaHistogramCounts1000(
+        histogram_prefix + "ModelIteration",
+        model_iteration_count_at_user_brightness_change_);
+  }
 }
 
 }  // namespace auto_screen_brightness

chrome/browser/chromeos/power/auto_screen_brightness/adapter.h

@@ -86,7 +86,7 @@ class Adapter : public AlsReader::Observer,
     double darkening_log_lux_threshold = 0.6;
     double stabilization_threshold = 0.15;
 
-    ModelCurve model_curve = ModelCurve::kLatest;
+    ModelCurve model_curve = ModelCurve::kPersonal;
 
     // Average ambient value is calculated over the past
     // |auto_brightness_als_horizon|. This is only used for brightness update,
@@ -98,6 +98,10 @@ class Adapter : public AlsReader::Observer,
         UserAdjustmentEffect::kDisableAuto;
 
     std::string metrics_key;
+
+    // If |model_curve| is |kPersonal| then we only use a personal curve if the
+    // the model has been trained at least |min_model_iteration_count|.
+    int min_model_iteration_count = 1;
   };
 
   // These values are persisted to logs. Entries should not be renumbered and
@@ -143,7 +147,10 @@ class Adapter : public AlsReader::Observer,
     kMinimalAlsChange = 7,
     // Adapter should only use personal curves but none is available.
     kMissingPersonalCurve = 8,
-    kMaxValue = kMissingPersonalCurve
+    // Adapter should only use a personal curve that has been trained for a min
+    // number of iterations.
+    kWaitingForTrainedPersonalCurve = 9,
+    kMaxValue = kWaitingForTrainedPersonalCurve
   };
 
   struct AdapterDecision {
@@ -359,6 +366,8 @@ class Adapter : public AlsReader::Observer,
   base::Optional<AdapterDecision>
       decision_at_first_recent_user_brightness_request_;
 
+  int model_iteration_count_at_user_brightness_change_ = 0;
+
   // The thresholds are calculated from the |average_log_ambient_lux_|.
   // They are only updated when brightness is changed (either by user or model).
   base::Optional<double> brightening_threshold_;

chrome/browser/chromeos/power/auto_screen_brightness/adapter_unittest.cc

@@ -922,9 +922,77 @@ TEST_F(AdapterTest, UsePersonalCurve) {
                        adapter_->GetCurrentAvgLogAlsForTesting().value()));
 }
 
+TEST_F(AdapterTest, UsePersonalCurveAfter3) {
+  std::map<std::string, std::string> params = default_params_;
+  params["model_curve"] = "1";
+  params["min_model_iteration_count"] = "3";
+
+  // Init modeller with only a global curve.
+  Init(AlsReader::AlsInitStatus::kSuccess, BrightnessMonitor::Status::kSuccess,
+       Model(global_curve_, base::nullopt, 0), GetTestModelConfig(), params);
+
+  EXPECT_EQ(adapter_->GetStatusForTesting(), Adapter::Status::kSuccess);
+
+  // Sufficient ALS data has come in but no brightness change is triggered
+  // because there is no personal curve.
+  ForwardTimeAndReportAls({1, 2, 3, 4, 5, 6, 7, 8});
+  EXPECT_EQ(test_observer_.num_changes(), 0);
+  EXPECT_EQ(adapter_->GetCurrentAvgLogAlsForTesting(), base::nullopt);
+
+  // Personal curve is received, it does not lead to any immediate brightness
+  // change.
+  thread_bundle_.FastForwardBy(base::TimeDelta::FromSeconds(1));
+  fake_modeller_.ReportModelTrained(*personal_curve_);
+  EXPECT_EQ(test_observer_.num_changes(), 0);
+  EXPECT_EQ(adapter_->GetCurrentAvgLogAlsForTesting(), base::nullopt);
+
+  // Another ALS comes in, which does not trigger a brightness change.
+  ReportAls(20);
+  EXPECT_EQ(test_observer_.num_changes(), 0);
+  EXPECT_EQ(adapter_->GetCurrentAvgLogAlsForTesting(), base::nullopt);
+
+  // Another training is done.
+  thread_bundle_.FastForwardBy(base::TimeDelta::FromSeconds(1));
+  fake_modeller_.ReportModelTrained(*personal_curve_);
+  EXPECT_EQ(test_observer_.num_changes(), 0);
+  EXPECT_EQ(adapter_->GetCurrentAvgLogAlsForTesting(), base::nullopt);
+
+  // Another ALS comes in, which does not trigger a brightness change.
+  ReportAls(30);
+  EXPECT_EQ(test_observer_.num_changes(), 0);
+  EXPECT_EQ(adapter_->GetCurrentAvgLogAlsForTesting(), base::nullopt);
+
+  // Another training is done.
+  const base::Optional<MonotoneCubicSpline> personal_curve_2 =
+      MonotoneCubicSpline::CreateMonotoneCubicSpline({-4, 12, 20},
+                                                     {30, 60, 100});
+  DCHECK(personal_curve_2);
+
+  thread_bundle_.FastForwardBy(base::TimeDelta::FromSeconds(1));
+  fake_modeller_.ReportModelTrained(*personal_curve_2);
+  EXPECT_EQ(test_observer_.num_changes(), 0);
+  EXPECT_EQ(adapter_->GetCurrentAvgLogAlsForTesting(), base::nullopt);
+
+  // Another ALS comes in, which triggers a brightness change.
+  ReportAls(40);
+  EXPECT_EQ(test_observer_.num_changes(), 1);
+  EXPECT_EQ(test_observer_.GetCause(),
+            power_manager::BacklightBrightnessChange_Cause_MODEL);
+
+  CheckAvgLog({7, 8, 20, 30, 40},
+              adapter_->GetCurrentAvgLogAlsForTesting().value());
+
+  // Brightness is changed according to the personal curve.
+  EXPECT_DOUBLE_EQ(test_observer_.GetBrightnessPercent(),
+                   personal_curve_2->Interpolate(
+                       adapter_->GetCurrentAvgLogAlsForTesting().value()));
+}
+
 TEST_F(AdapterTest, UseGlobalCurve) {
   std::map<std::string, std::string> params = default_params_;
   params["model_curve"] = "0";
+  // This param has no effect.
+  params["min_model_iteration_count"] = "3";
 
   Init(AlsReader::AlsInitStatus::kSuccess, BrightnessMonitor::Status::kSuccess,
        Model(global_curve_, personal_curve_, 0), GetTestModelConfig(), params);

tools/metrics/histograms/enums.xml

@@ -4238,6 +4238,7 @@ Unknown properties are collapsed to zero. -->
   <int value="6" label="FluctuatingAlsDecrease"/>
   <int value="7" label="MinimalAlsChange"/>
   <int value="8" label="MissingPersonalCurve"/>
+  <int value="9" label="WaitingForTrainedPersonalCurve"/>
 </enum>
 
 <enum name="AutoScreenBrightnessParameterError">

tools/metrics/histograms/histograms.xml

@@ -10604,6 +10604,19 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram base="true"
+    name="AutoScreenBrightness.AdapterDecisionAtUserChange.ModelIteration"
+    units="count" expires_after="2019-12-31">
+<!-- Name completed by histogram_suffixes name="AdapterDecision" -->
+
+  <owner>jiameng@chromium.org</owner>
+  <summary>
+    When user changes brightness manually, we will ask the model whether it also
+    thinks brightness should be changed. We also log the number of model
+    iterations if we've set to use personal curve only. Chrome OS only.
+  </summary>
+</histogram>
+
 <histogram
     name="AutoScreenBrightness.AdapterDecisionAtUserChange.NoBrightnessChange.Cause"
     enum="AutoScreenBrightnessNoBrightnessChangeCause"
@@ -10638,6 +10651,12 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="AutoScreenBrightness.BrightnessChange.Cause"
+    enum="AutoScreenBrightnessBrightnessChangeCause" expires_after="2019-12-31">
+  <owner>jiameng@chromium.org</owner>
+  <summary>Reason for the model to change brightness. Chrome OS only.</summary>
+</histogram>
+
 <histogram name="AutoScreenBrightness.BrightnessChange.ElapsedTime" units="ms"
     expires_after="2019-12-31">
   <owner>jiameng@chromium.org</owner>
@@ -10646,6 +10665,15 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="AutoScreenBrightness.BrightnessChange.ModelIteration"
+    units="count" expires_after="2019-12-31">
+  <owner>jiameng@chromium.org</owner>
+  <summary>
+    Number of model iterations when brightness is changed by a personal curve.
+    Chrome OS only.
+  </summary>
+</histogram>
+
 <histogram name="AutoScreenBrightness.BrightnessMonitorStatus"
     enum="AutoScreenBrightnessBrightnessMonitorStatus"
     expires_after="2019-12-31">
@@ -145912,6 +145940,8 @@ should be kept until we use this API.  -->
       name="AutoScreenBrightness.AdapterDecisionAtUserChange.Darken.AlsDelta"/>
   <affected-histogram
       name="AutoScreenBrightness.AdapterDecisionAtUserChange.Darken.AlsStd"/>
+  <affected-histogram
+      name="AutoScreenBrightness.AdapterDecisionAtUserChange.ModelIteration"/>
   <affected-histogram
       name="AutoScreenBrightness.AdapterDecisionAtUserChange.Unknown.AlsStd"/>
 </histogram_suffixes>