[On-device adaptive brightness] Change default global curve and brightness thresholds.

The global curve has been updated based on preliminary experiments and current
device-specific ALS->brightness config.

Bug: 881215
Change-Id: I19e00e328e0f3dd8afff86766127d268a9f58248
Reviewed-on: https://chromium-review.googlesource.com/c/1351332
Commit-Queue: Jia Meng <jiameng@chromium.org>
Reviewed-by: Andrew Moylan <amoylan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611434}

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

@@ -48,13 +48,13 @@ class Adapter : public AlsReader::Observer,
     kMaxValue = kLatest
   };
 
-  // TODO(jiameng): we currently use past 2 seconds of ambient values to
+  // TODO(jiameng): we currently use past 5 seconds of ambient values to
   // calculate average ambient when we predict optimal brightness. This is
   // shorter than the duration used for training data (10 seconds), because it's
   // important that we can quickly adjust the brightness when ambient value
   // changes. This duration should be revised.
   static constexpr base::TimeDelta kAmbientLightShortHorizon =
-      base::TimeDelta::FromSeconds(2);
+      base::TimeDelta::FromSeconds(5);
 
   // Size of |ambient_light_values_|.
   static constexpr int kNumberAmbientValuesToTrack =
@@ -69,16 +69,16 @@ class Adapter : public AlsReader::Observer,
     // from the current value before brightness could be changed: brightness
     // will actually be changed if |min_time_between_brightness_changes| has
     // passed from the previous change.
-    double brightening_lux_threshold_ratio = 0.1;
-    double darkening_lux_threshold_ratio = 0.2;
+    double brightening_lux_threshold_ratio = 0.3;
+    double darkening_lux_threshold_ratio = 0.4;
 
     // If average ambient value changes by more than the "immediate" thresholds
     // then brightness transition will happen immediately, without waiting for
     // |min_time_between_brightness_changes| to elapse. This value should be
     // greater than or equal to the max of brightening/darkening thresholds
     // above.
-    double immediate_brightening_lux_threshold_ratio = 0.3;
-    double immediate_darkening_lux_threshold_ratio = 0.4;
+    double immediate_brightening_lux_threshold_ratio = 0.4;
+    double immediate_darkening_lux_threshold_ratio = 0.5;
 
     // Whether brightness should be set to the predicted value when the first
     // ambient reading comes in. If false, we'll wait for

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

@@ -427,6 +427,7 @@ TEST_F(AdapterTest, UserBrightnessRequestBeforeAnyModelUpdate) {
 TEST_F(AdapterTest, BrightnessLuxThresholds) {
   Init(AlsReader::AlsInitStatus::kSuccess, BrightnessMonitor::Status::kSuccess,
        global_curve_, personal_curve_, default_params_);
+  EXPECT_EQ(Adapter::kNumberAmbientValuesToTrack, 5);
 
   EXPECT_EQ(adapter_->GetStatusForTesting(), Adapter::Status::kSuccess);
   EXPECT_TRUE(adapter_->GetGlobalCurveForTesting());
@@ -457,7 +458,8 @@ TEST_F(AdapterTest, BrightnessLuxThresholds) {
   // A 3rd ALS comes in, but still not enough to trigger brightness change.
   fake_als_reader_.ReportAmbientLightUpdate(15);
   EXPECT_EQ(test_observer_.num_changes(), 1);
-  EXPECT_DOUBLE_EQ(adapter_->GetAverageAmbientForTesting(), (21 + 15) / 2.0);
+  EXPECT_DOUBLE_EQ(adapter_->GetAverageAmbientForTesting(),
+                   (20 + 21 + 15) / 3.0);
   EXPECT_DOUBLE_EQ(adapter_->GetBrighteningThresholdForTesting(), 22);
   EXPECT_DOUBLE_EQ(adapter_->GetDarkeningThresholdForTesting(), 16);
 
@@ -467,15 +469,26 @@ TEST_F(AdapterTest, BrightnessLuxThresholds) {
   scoped_task_environment_.RunUntilIdle();
 
   EXPECT_EQ(test_observer_.num_changes(), 2);
-  EXPECT_EQ(Adapter::kNumberAmbientValuesToTrack, 2);
-  const double expected_average_ambient =
-      (15.0 + 7.0) / Adapter::kNumberAmbientValuesToTrack;
+  const double expected_average_ambient = (20 + 21 + 15 + 7) / 4.0;
   EXPECT_DOUBLE_EQ(adapter_->GetAverageAmbientForTesting(),
                    expected_average_ambient);
   EXPECT_DOUBLE_EQ(adapter_->GetBrighteningThresholdForTesting(),
                    expected_average_ambient * 1.1);
   EXPECT_DOUBLE_EQ(adapter_->GetDarkeningThresholdForTesting(),
                    expected_average_ambient * 0.8);
+
+  // Next check |ambient_light_values_| has capacity
+  // |Adapter::kNumberAmbientValuesToTrack|.
+  fake_als_reader_.ReportAmbientLightUpdate(8);
+  scoped_task_environment_.RunUntilIdle();
+  EXPECT_DOUBLE_EQ(adapter_->GetAverageAmbientForTesting(),
+                   (20 + 21 + 15 + 7 + 8) / 5.0);
+
+  fake_als_reader_.ReportAmbientLightUpdate(9);
+  scoped_task_environment_.RunUntilIdle();
+
+  EXPECT_DOUBLE_EQ(adapter_->GetAverageAmbientForTesting(),
+                   (21 + 15 + 7 + 8 + 9) / 5.0);
 }
 
 TEST_F(AdapterTest, ImmediateBrightnessTransitionThresholds) {
@@ -530,7 +543,7 @@ TEST_F(AdapterTest, BrightnessNotUpdatedOnStartup) {
   scoped_task_environment_.RunUntilIdle();
   EXPECT_EQ(test_observer_.num_changes(), 0);
 
-  scoped_task_environment_.FastForwardBy(base::TimeDelta::FromSeconds(2));
+  scoped_task_environment_.FastForwardBy(base::TimeDelta::FromSeconds(5));
   EXPECT_EQ(test_observer_.num_changes(), 0);
 
   // 2nd ALS comes in so that we have |kAmbientLightShortHorizonSeconds| of

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

@@ -31,7 +31,8 @@ namespace auto_screen_brightness {
 namespace {
 
 // Creates a global/default brightness curve.
-// TODO(crbug.com/881215): add actual default curve and then add unit test too.
+// TODO(crbug.com/881215): default curve may be revised, if so, need to update
+// unit tests as well.
 MonotoneCubicSpline CreateGlobalCurve() {
   const std::string global_curve = GetFieldTrialParamValueByFeature(
       features::kAutoScreenBrightness, "global_curve");
@@ -43,8 +44,14 @@ MonotoneCubicSpline CreateGlobalCurve() {
     // TODO(jiameng): log error to UMA.
   }
 
-  const std::vector<double> default_log_lux = {0, 100};
-  const std::vector<double> default_brightness = {50, 100};
+  const std::vector<double> default_log_lux = {
+      3.69, 4.83, 6.54, 7.68, 8.25, 8.82,
+  };
+
+  const std::vector<double> default_brightness = {
+      36.14, 47.62, 85.83, 93.27, 93.27, 100,
+  };
+
   return MonotoneCubicSpline(default_log_lux, default_brightness);
 }
 

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

@@ -561,7 +561,13 @@ TEST_F(ModellerImplTest, GlobaCurveFromInvalidExperimentParam) {
       features::kAutoScreenBrightness, {{"global_curve", global_curve_spec}});
 
   // Defined by default values.
-  const MonotoneCubicSpline expected_global_curve({0, 100}, {50, 100});
+  const MonotoneCubicSpline expected_global_curve(
+      {
+          3.69, 4.83, 6.54, 7.68, 8.25, 8.82,
+      },
+      {
+          36.14, 47.62, 85.83, 93.27, 93.27, 100,
+      });
 
   Init(AlsReader::AlsInitStatus::kSuccess, BrightnessMonitor::Status::kSuccess);
   EXPECT_EQ(modeller_->GetGlobalCurveForTesting(), expected_global_curve);