Omnibox - Boost Frequency Scores Based on Number of Matching Pages

components/omnibox/browser/scored_history_match.cc

Index: components/omnibox/browser/scored_history_match.cc
diff --git a/components/omnibox/browser/scored_history_match.cc b/components/omnibox/browser/scored_history_match.cc
index bdde8e547430e18c6a9659cc48203cde566edf58..534b194eab14072354c7060533b30a0c9294dc61 100644
--- a/components/omnibox/browser/scored_history_match.cc
+++ b/components/omnibox/browser/scored_history_match.cc
@@ -109,6 +109,8 @@ float ScoredHistoryMatch::bookmark_value_;
 float ScoredHistoryMatch::typed_value_;
 bool ScoredHistoryMatch::fix_few_visits_bug_;
 bool ScoredHistoryMatch::frequency_uses_sum_;
+OmniboxFieldTrial::NumMatchesScores*
+    ScoredHistoryMatch::num_matches_to_document_specificity_score_ = nullptr;
 size_t ScoredHistoryMatch::max_visits_to_score_;
 bool ScoredHistoryMatch::allow_tld_matches_;
 bool ScoredHistoryMatch::allow_scheme_matches_;
@@ -133,8 +135,8 @@ ScoredHistoryMatch::ScoredHistoryMatch()
                          WordStarts(),
                          RowWordStarts(),
                          false,
-                         base::Time::Max()) {
-}
+                         1,
+                         base::Time::Max()) {}
 
 ScoredHistoryMatch::ScoredHistoryMatch(
     const history::URLRow& row,
@@ -144,6 +146,7 @@ ScoredHistoryMatch::ScoredHistoryMatch(
     const WordStarts& terms_to_word_starts_offsets,
     const RowWordStarts& word_starts,
     bool is_url_bookmarked,
+    size_t num_matching_pages,
     base::Time now)
     : HistoryMatch(row, 0, false, false), raw_score(0) {
   // NOTE: Call Init() before doing any validity checking to ensure that the
@@ -261,8 +264,11 @@ ScoredHistoryMatch::ScoredHistoryMatch(
   const float topicality_score = GetTopicalityScore(
       terms_vector.size(), url, terms_to_word_starts_offsets, word_starts);
   const float frequency_score = GetFrequency(now, is_url_bookmarked, visits);
-  raw_score = base::saturated_cast<int>(GetFinalRelevancyScore(
-      topicality_score, frequency_score, *hqp_relevance_buckets_));
+  const float specificity_score =
+      GetDocumentSpecificityScore(num_matching_pages);
+  raw_score = base::saturated_cast<int>(
+      GetFinalRelevancyScore(topicality_score, frequency_score,
+                             specificity_score, *hqp_relevance_buckets_));
 
   if (also_do_hup_like_scoring_ && likely_can_inline) {
     // HistoryURL-provider-like scoring gives any match that is
@@ -412,6 +418,10 @@ void ScoredHistoryMatch::Init() {
   max_visits_to_score_ = OmniboxFieldTrial::HQPMaxVisitsToScore();
   frequency_uses_sum_ = OmniboxFieldTrial::HQPFreqencyUsesSum();
   fix_few_visits_bug_ = OmniboxFieldTrial::HQPFixFewVisitsBug();
+  num_matches_to_document_specificity_score_ =
+      new OmniboxFieldTrial::NumMatchesScores();
+  (*num_matches_to_document_specificity_score_) =
+      OmniboxFieldTrial::HQPNumMatchesScores();
   allow_tld_matches_ = OmniboxFieldTrial::HQPAllowMatchInTLDValue();
   allow_scheme_matches_ = OmniboxFieldTrial::HQPAllowMatchInSchemeValue();
   num_title_words_to_allow_ = OmniboxFieldTrial::HQPNumTitleWordsToAllow();
@@ -616,18 +626,32 @@ float ScoredHistoryMatch::GetFrequency(const base::Time& now,
          ScoredHistoryMatch::max_visits_to_score_;
 }
 
+float ScoredHistoryMatch::GetDocumentSpecificityScore(
+    const size_t num_matching_pages) const {
+  // The floating point value below doesn't matter.

[Peter Kasting, 2016/12/06 05:19:30]

I'm not sure that's true.

Since upper_bound() returns the first element greater than the given value, if
the server sends a score of 1.0 or less for a particular number of pages, this
will fail to match.

A more accurate comment would probably be "The floating point value below must
be less than the lowest score the server would send down" or similar, and a
safer value might be -1.

[Mark P, 2016/12/08 00:21:31]

Good point.  I never imagined a field trial specifying a score of less than 1,
but having an appropriate comment and defensive code makes sense.  Who knows
what I'll want in the future?  :-) Done.

+  OmniboxFieldTrial::NumMatchesScores::const_iterator it =
+      std::upper_bound(num_matches_to_document_specificity_score_->begin(),
+                       num_matches_to_document_specificity_score_->end(),
+                       std::pair<size_t, double>{num_matching_pages, 1.0});
+  if (it == num_matches_to_document_specificity_score_->end())
+    return 1.0;
+  return it->second;

[Peter Kasting, 2016/12/06 05:19:30]

Nit: Could use ?:

[Mark P, 2016/12/08 00:21:31]

Done (after reversing the order, as that read better to me).

[Peter Kasting, 2016/12/08 00:51:40]

My concern with the order reversal is that it sort of violates "don't have
'else' with a negated condition, or the 'else' reads like a double-negative". 
Except here the "else" is the ':'.

So I'd put it back the other way, but up to you.

[Mark P, 2016/12/08 04:37:35]

I understand the point, but I find != end to read to me like a positive
(exists), and when I read == end, I have to mentally reverse it (!exists).

+};
+
 // static
 float ScoredHistoryMatch::GetFinalRelevancyScore(
     float topicality_score,
     float frequency_score,
+    float specificity_score,
     const std::vector<ScoreMaxRelevance>& hqp_relevance_buckets) {
   DCHECK(hqp_relevance_buckets.size() > 0);
   DCHECK_EQ(hqp_relevance_buckets[0].first, 0.0);
 
   if (topicality_score == 0)
     return 0;
-  // Here's how to interpret intermediate_score: Suppose the omnibox
-  // has one input term.  Suppose we have a URL for which the omnibox
+  // Here's how to interpret intermediate_score: Suppose the omnibox has one
+  // input term.  Suppose the input matches many documents.  (This implies
+  // specificity_score == 1.0.)  Suppose we have a URL for which the omnibox
   // input term has a single URL hostname hit at a word boundary.  (This
   // implies topicality_score = 1.0.).  Then the intermediate_score for
   // this URL will depend entirely on the frequency_score with
@@ -651,7 +675,8 @@ float ScoredHistoryMatch::GetFinalRelevancyScore(
   //
   // The score maxes out at 1399 (i.e., cannot beat a good inlineable result
   // from HistoryURL provider).
-  const float intermediate_score = topicality_score * frequency_score;
+  const float intermediate_score =
+      topicality_score * frequency_score * specificity_score;
 
   // Find the threshold where intermediate score is greater than bucket.
   size_t i = 1;