HUP Experimental Scoring framework.

High level summary:
(a) Introduce a new set of Finch variation params and use it in the Omnibox bundled experiment
(b) Group together HUP scoring params in a HUPScoringParams struct and initialize it based on the new experiment params
(c) Modify HUP scoring by applying optional demotion 

This change is fairly safe because of the following reasons:
(1) It is disabled by default
(2) It never changes the relative order of HUP matches
(3) It can only demote a HUP match
(4) It is fairly isolated and unobtrusive

BUG=295756
TESTS=OmniboxFieldTrialTest,HistoryURLProviderTest

Review URL: https://codereview.chromium.org/23707058

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242569 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 85 insertions, 0 deletions

diff --git a/chrome/browser/omnibox/omnibox_field_trial.h b/chrome/browser/omnibox/omnibox_field_trial.h
index 9e9ee55..a75eccc 100644
--- a/chrome/browser/omnibox/omnibox_field_trial.h
+++ b/chrome/browser/omnibox/omnibox_field_trial.h
@@ -15,6 +15,74 @@
 #include "chrome/browser/autocomplete/autocomplete_input.h"
 #include "chrome/common/autocomplete_match_type.h"
 
+namespace base {
+class TimeDelta;
+}
+
+// The set of parameters customizing the HUP scoring.
+struct HUPScoringParams {
+  // A set of parameters describing how to cap a given count score.  First,
+  // we apply a half-life based decay of the given count and then find the
+  // maximum relevance score in the corresponding bucket list.
+  class ScoreBuckets {
+   public:
+    // (decayed_count, max_relevance) pair.
+    typedef std::pair<double, int> CountMaxRelevance;
+
+    ScoreBuckets();
+    ~ScoreBuckets();
+
+    // Computes a half-life time decay given the |elapsed_time|.
+    double HalfLifeTimeDecay(const base::TimeDelta& elapsed_time) const;
+
+    int relevance_cap() const { return relevance_cap_; }
+    void set_relevance_cap(int relevance_cap) {
+      relevance_cap_ = relevance_cap;
+    }
+
+    int half_life_days() const { return half_life_days_; }
+    void set_half_life_days(int half_life_days) {
+      half_life_days_ = half_life_days;
+    }
+
+    std::vector<CountMaxRelevance>& buckets() { return buckets_; }
+    const std::vector<CountMaxRelevance>& buckets() const { return buckets_; }
+
+   private:
+    // History matches with relevance score greater or equal to |relevance_cap_|
+    // are not affected by this experiment.
+    // Set to -1, if there is no relevance cap in place and all matches are
+    // subject to demotion.
+    int relevance_cap_;
+
+    // Half life time for a decayed count as measured since the last visit.
+    // Set to -1 if not used.
+    int half_life_days_;
+
+    // The relevance score caps for given decayed count values.
+    // Each pair (decayed_count, max_score) indicates what the maximum relevance
+    // score is of a decayed count equal or greater than decayed_count.
+    //
+    // Consider this example:
+    //   [(1, 1000), (0.5, 500), (0, 100)]
+    // If decayed count is 2 (which is >= 1), the corresponding match's maximum
+    // relevance will be capped at 1000.  In case of 0.5, the score is capped
+    // at 500.  Anything below 0.5 is capped at 100.
+    //
+    // This list is sorted by the pair's first element in descending order.
+    std::vector<CountMaxRelevance> buckets_;
+  };
+
+  HUPScoringParams() : experimental_scoring_enabled(false) {}
+
+  bool experimental_scoring_enabled;
+
+  ScoreBuckets typed_count_buckets;
+
+  // Used only when the typed count is 0.
+  ScoreBuckets visited_count_buckets;
+};
+
 // This class manages the Omnibox field trials.
 class OmniboxFieldTrial {
  public:
@@ -175,6 +243,14 @@ class OmniboxFieldTrial {
       AutocompleteInput::PageClassification current_page_classification);
 
   // ---------------------------------------------------------
+  // For the HistoryURL provider new scoring experiment that is part of the
+  // bundled omnibox field trial.
+
+  // Initializes the HUP |scoring_params| based on the active HUP scoring
+  // experiment.  If there is no such experiment, this function simply sets
+  // |scoring_params|->experimental_scoring_enabled to false.
+  static void GetExperimentalHUPScoringParams(HUPScoringParams* scoring_params);
+
   // For the HQPBookmarkValue experiment that's part of the
   // bundled omnibox field trial.
 
@@ -228,6 +304,15 @@ class OmniboxFieldTrial {
   // Rule values.
   static const char kReorderForLegalDefaultMatchRuleEnabled[];
 
+  // Parameter names used by the HUP new scoring experiments.
+  static const char kHUPNewScoringEnabledParam[];
+  static const char kHUPNewScoringTypedCountRelevanceCapParam[];
+  static const char kHUPNewScoringTypedCountHalfLifeTimeParam[];
+  static const char kHUPNewScoringTypedCountScoreBucketsParam[];
+  static const char kHUPNewScoringVisitedCountRelevanceCapParam[];
+  static const char kHUPNewScoringVisitedCountHalfLifeTimeParam[];
+  static const char kHUPNewScoringVisitedCountScoreBucketsParam[];
+
  private:
   friend class OmniboxFieldTrialTest;