Tweaks the ranking of past searches so they get autocompleted.

If you don't like the scoring I've given them, please suggest an
alternative.

BUG=61518
TEST=none

Review URL: http://codereview.chromium.org/4751001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@65566 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 29 insertions, 9 deletions

diff --git a/chrome/browser/autocomplete/autocomplete.h b/chrome/browser/autocomplete/autocomplete.h
index 25c8341..4f24852 100644
--- a/chrome/browser/autocomplete/autocomplete.h
+++ b/chrome/browser/autocomplete/autocomplete.h
@@ -42,10 +42,11 @@
 // --------------------------------------------------------------------|-----
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
 // HistoryURL (exact or inline autocomplete match)                     | 1400
+// Search Primary Provider (past query in history within 2 days)       | 1399**
 // Search Primary Provider (what you typed)                            | 1300
 // HistoryURL (what you typed)                                         | 1200
 // Keyword (substituting, exact match)                                 | 1100
-// Search Primary Provider (past query in history)                     | 1050--
+// Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (navigational suggestion)                   |  800++
@@ -63,10 +64,11 @@
 // --------------------------------------------------------------------|-----
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
 // HistoryURL (exact or inline autocomplete match)                     | 1400
+// Search Primary Provider (past query in history within 2 days)       | 1399**
 // HistoryURL (what you typed)                                         | 1200
 // Search Primary Provider (what you typed)                            | 1150
 // Keyword (substituting, exact match)                                 | 1100
-// Search Primary Provider (past query in history)                     | 1050--
+// Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (navigational suggestion)                   |  800++
@@ -102,8 +104,9 @@
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
 // Keyword (substituting, exact match)                                 | 1450
 // HistoryURL (exact or inline autocomplete match)                     | 1400
+// Search Primary Provider (past query in history within 2 days)       | 1399**
 // Search Primary Provider (what you typed)                            | 1300
-// Search Primary Provider (past query in history)                     | 1050--
+// Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (navigational suggestion)                   |  800++
@@ -119,8 +122,9 @@
 //
 // FORCED_QUERY input type:
 // --------------------------------------------------------------------|-----
+// Search Primary Provider (past query in history within 2 days)       | 1399**
 // Search Primary Provider (what you typed)                            | 1300
-// Search Primary Provider (past query in history)                     | 1050--
+// Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // Search Primary Provider (navigational suggestion)                   |  800++
 // HistoryContents (any match in title of nonstarred page)             |  700++
@@ -140,6 +144,8 @@
 // ++: a series of matches with relevance from n up to (n + max_matches).
 // --: relevance score falls off over time (discounted 50 points @ 15 minutes,
 //     450 points @ two weeks)
+// --: relevance score falls off over two days (discounted 99 points after two
+//     days).
 
 class AutocompleteInput;
 struct AutocompleteMatch;
diff --git a/chrome/browser/autocomplete/search_provider.cc b/chrome/browser/autocomplete/search_provider.cc
index 408e647..ef8eb13 100644
--- a/chrome/browser/autocomplete/search_provider.cc
+++ b/chrome/browser/autocomplete/search_provider.cc
@@ -565,11 +565,25 @@ int SearchProvider::CalculateRelevanceForWhatYouTyped() const {
 
 int SearchProvider::CalculateRelevanceForHistory(const Time& time,
                                                  bool is_keyword) const {
-  // The relevance of past searches falls off over time.  This curve is chosen
-  // so that the relevance of a search 15 minutes ago is discounted about 50
-  // points, while the relevance of a search two weeks ago is discounted about
-  // 450 points.
-  const double elapsed_time = std::max((Time::Now() - time).InSecondsF(), 0.);
+  // The relevance of past searches falls off over time. There are two distinct
+  // equations used. If the first equation is used (searches to the primary
+  // provider with a type other than URL) the score starts at 1399 and falls to
+  // 1300. If the second equation is used the relevance of a search 15 minutes
+  // ago is discounted about 50 points, while the relevance of a search two
+  // weeks ago is discounted about 450 points.
+  double elapsed_time = std::max((Time::Now() - time).InSecondsF(), 0.);
+
+  if (providers_.is_primary_provider(is_keyword) &&
+      input_.type() != AutocompleteInput::URL) {
+    // Searches with the past two days get a different curve.
+    const double autocomplete_time= 2 * 24 * 60 * 60;
+    if (elapsed_time < autocomplete_time) {
+      return 1399 - static_cast<int>(99 *
+          std::pow(elapsed_time / autocomplete_time, 2.5));
+    }
+    elapsed_time -= autocomplete_time;
+  }
+
   const int score_discount =
       static_cast<int>(6.5 * std::pow(elapsed_time, 0.3));