Remove hit weight experiment.

Results of the experiment show that higher hit weights yield greater coverage, but at the expense of accuracy. The decreased accuracy outweighs the increased coverage.

BUG=111069


Review URL: https://chromiumcodereview.appspot.com/10453013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@139086 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 5 insertions, 43 deletions

diff --git a/chrome/browser/predictors/autocomplete_action_predictor.cc b/chrome/browser/predictors/autocomplete_action_predictor.cc
index a64d04f..8a2f65c 100644
--- a/chrome/browser/predictors/autocomplete_action_predictor.cc
+++ b/chrome/browser/predictors/autocomplete_action_predictor.cc
@@ -75,8 +75,6 @@ namespace predictors {
 
 const int AutocompleteActionPredictor::kMaximumDaysToKeepEntry = 14;
 
-double AutocompleteActionPredictor::hit_weight_ = 1.0;
-
 AutocompleteActionPredictor::AutocompleteActionPredictor(Profile* profile)
     : profile_(profile),
       table_(PredictorDatabaseFactory::GetForProfile(
@@ -242,8 +240,7 @@ void AutocompleteActionPredictor::OnOmniboxOpenedUrl(
   const AutocompleteMatch& match = log.result.match_at(log.selected_index);
 
   UMA_HISTOGRAM_BOOLEAN(
-      StringPrintf("Prerender.OmniboxNavigationsCouldPrerender_%.1f%s",
-                   get_hit_weight(),
+      StringPrintf("Prerender.OmniboxNavigationsCouldPrerender_%s",
                    prerender::PrerenderManager::GetModeString()).c_str(),
       prerender::IsOmniboxEnabled(profile_));
 
@@ -424,7 +421,7 @@ double AutocompleteActionPredictor::CalculateConfidenceForDbEntry(
   if (value.number_of_hits < kMinimumNumberOfHits)
     return 0.0;
 
-  const double number_of_hits = value.number_of_hits * hit_weight_;
+  const double number_of_hits = static_cast<double>(value.number_of_hits);
   return number_of_hits / (number_of_hits + value.number_of_misses);
 }
 
diff --git a/chrome/browser/predictors/autocomplete_action_predictor.h b/chrome/browser/predictors/autocomplete_action_predictor.h
index 8827b48..42353fd 100644
--- a/chrome/browser/predictors/autocomplete_action_predictor.h
+++ b/chrome/browser/predictors/autocomplete_action_predictor.h
@@ -55,9 +55,6 @@ class AutocompleteActionPredictor
   explicit AutocompleteActionPredictor(Profile* profile);
   virtual ~AutocompleteActionPredictor();
 
-  static void set_hit_weight(double weight) { hit_weight_ = weight; }
-  static double get_hit_weight() { return hit_weight_; }
-
   // Registers an AutocompleteResult for a given |user_text|. This will be used
   // when the user navigates from the Omnibox to determine early opportunities
   // to predict their actions.
@@ -122,11 +119,6 @@ class AutocompleteActionPredictor
 
   static const int kMaximumDaysToKeepEntry;
 
-  // Multiplying factor applied to the |number_of_hits| for a database entry
-  // when calculating the confidence. It is currently set by a field trial so is
-  // static. Once the field trial ends, this will be a constant value.
-  static double hit_weight_;
-
   // NotificationObserver
   virtual void Observe(int type,
                        const content::NotificationSource& source,
diff --git a/chrome/browser/prerender/prerender_field_trial.cc b/chrome/browser/prerender/prerender_field_trial.cc
index 228c6cd..43c71f6 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -200,26 +200,6 @@ void ConfigureOmniboxPrerender() {
           2012, 12, 30, &g_omnibox_trial_default_group_number));
   omnibox_prerender_trial->AppendGroup("OmniboxPrerenderDisabled",
                                        kDisabledProbability);
-
-  // Field trial to set weighting of hits.
-  const base::FieldTrial::Probability kFourProbability = 33;
-  const base::FieldTrial::Probability kEightProbability = 33;
-
-  scoped_refptr<base::FieldTrial> weighting_trial(
-      base::FieldTrialList::FactoryGetFieldTrial(
-          "OmniboxPrerenderHitWeightingTrial", kDivisor,
-          "OmniboxPrerenderWeight1.0", 2012, 8, 30, NULL));
-  const int kOmniboxWeightFourGroup =
-      weighting_trial->AppendGroup("OmniboxPrerenderWeight4.0",
-                                   kFourProbability);
-  const int kOmniboxWeightEightGroup =
-      weighting_trial->AppendGroup("OmniboxPrerenderWeight8.0",
-                                   kEightProbability);
-  const int group = weighting_trial->group();
-  if (group == kOmniboxWeightFourGroup)
-    predictors::AutocompleteActionPredictor::set_hit_weight(4.0);
-  else if (group == kOmniboxWeightEightGroup)
-    predictors::AutocompleteActionPredictor::set_hit_weight(8.0);
 }
 
 bool IsOmniboxEnabled(Profile* profile) {
diff --git a/chrome/browser/prerender/prerender_histograms.cc b/chrome/browser/prerender/prerender_histograms.cc
index f150608..19b62c7 100644
--- a/chrome/browser/prerender/prerender_histograms.cc
+++ b/chrome/browser/prerender/prerender_histograms.cc
@@ -48,10 +48,7 @@ std::string GetHistogramName(Origin origin, uint8 experiment_id,
 
   switch (origin) {
     case ORIGIN_OMNIBOX:
-      return ComposeHistogramName(
-          StringPrintf("omnibox_%.1f",
-                       AutocompleteActionPredictor::get_hit_weight()).c_str(),
-          name);
+      return ComposeHistogramName("omnibox", name);
     case ORIGIN_LINK_REL_PRERENDER:
       return ComposeHistogramName("web", name);
     case ORIGIN_GWS_PRERENDER:  // Handled above.
@@ -154,8 +151,7 @@ void PrerenderHistograms::RecordPrerender(Origin origin, const GURL& url) {
 void PrerenderHistograms::RecordPrerenderStarted(Origin origin) const {
   if (OriginIsOmnibox(origin)) {
     UMA_HISTOGRAM_COUNTS(
-        StringPrintf("Prerender.OmniboxPrerenderCount_%.1f%s",
-                     AutocompleteActionPredictor::get_hit_weight(),
+        StringPrintf("Prerender.OmniboxPrerenderCount_%s",
                      PrerenderManager::GetModeString()).c_str(),
         1);
   }
@@ -164,8 +160,7 @@ void PrerenderHistograms::RecordPrerenderStarted(Origin origin) const {
 void PrerenderHistograms::RecordUsedPrerender(Origin origin) const {
   if (OriginIsOmnibox(origin)) {
     UMA_HISTOGRAM_COUNTS(
-        StringPrintf("Prerender.OmniboxNavigationsUsedPrerenderCount_%.1f%s",
-                     AutocompleteActionPredictor::get_hit_weight(),
+        StringPrintf("Prerender.OmniboxNavigationsUsedPrerenderCount_%s",
                      PrerenderManager::GetModeString()).c_str(),
         1);
   }
diff --git a/chrome/browser/resources/predictors/predictors.js b/chrome/browser/resources/predictors/predictors.js
index 5a722e8..69ff649 100644
--- a/chrome/browser/resources/predictors/predictors.js
+++ b/chrome/browser/resources/predictors/predictors.js
@@ -74,7 +74,6 @@ function updateDatabaseView(database) {
     }
   }
   $('countBanner').textContent = 'Entries: ' + databaseSection.children.length;
-  $('countBanner').textContent += '  Hit Weight: ' + database.hit_weight;
 }
 
 document.addEventListener('DOMContentLoaded',
diff --git a/chrome/browser/ui/webui/predictors/predictors_handler.cc b/chrome/browser/ui/webui/predictors/predictors_handler.cc
index 173e7a8..36c6945 100644
--- a/chrome/browser/ui/webui/predictors/predictors_handler.cc
+++ b/chrome/browser/ui/webui/predictors/predictors_handler.cc
@@ -48,7 +48,6 @@ void PredictorsHandler::RequestAutocompleteActionPredictorDb(
       db->Append(entry);
     }
     dict.Set("db", db);
-    dict.SetDouble("hit_weight", AutocompleteActionPredictor::get_hit_weight());
   }
 
   web_ui()->CallJavascriptFunction("updateDatabaseTable", dict);