Track confidence calculations better. Reduce minimum user text length.

chrome/browser/autocomplete/network_action_predictor.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/autocomplete/network_action_predictor.h"
 
 #include <math.h>
 
 #include <vector>
 
@@ skipping 17 matching lines @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 
 namespace {
 
 const float kConfidenceCutoff[] = {
   0.8f,
   0.5f
 };
 
-const size_t kMinimumUserTextLength = 2;
+const size_t kMinimumUserTextLength = 1;
 const int kMinimumNumberOfHits = 3;
 
 COMPILE_ASSERT(arraysize(kConfidenceCutoff) ==
                NetworkActionPredictor::LAST_PREDICT_ACTION,
                ConfidenceCutoff_count_mismatch);
 
 bool GetURLRowForAutocompleteMatch(Profile* profile,
                                    const AutocompleteMatch& match,
                                    history::URLRow* url_row) {
   DCHECK(url_row);
@@ skipping 75 matching lines @@
 }
 
 void NetworkActionPredictor::ClearTransitionalMatches() {
   transitional_matches_.clear();
 }
 
 // Given a match, return a recommended action.
 NetworkActionPredictor::Action NetworkActionPredictor::RecommendAction(
     const string16& user_text,
     const AutocompleteMatch& match) const {
-  double confidence = 0.0;
+  DCHECK(prerender::GetOmniboxHeuristicToUse() ==
+           prerender::OMNIBOX_HEURISTIC_EXACT ||
+         prerender::GetOmniboxHeuristicToUse() ==
+           prerender::OMNIBOX_HEURISTIC_EXACT_FULL);
 
-  switch (prerender::GetOmniboxHeuristicToUse()) {
-    case prerender::OMNIBOX_HEURISTIC_EXACT:
-    case prerender::OMNIBOX_HEURISTIC_EXACT_FULL:
-      confidence = ExactAlgorithm(user_text, match);
-      break;
-    default:
-      NOTREACHED();
-      break;
-  };
-
+  bool is_in_db = false;
+  const double confidence = CalculateConfidence(user_text, match, &is_in_db);
   DCHECK(confidence >= 0.0 && confidence <= 1.0);
 
-  UMA_HISTOGRAM_COUNTS_100("NetworkActionPredictor.Confidence_" +
-                           prerender::GetOmniboxHistogramSuffix(),
-                           confidence * 100);
+  if (is_in_db) {
+    UMA_HISTOGRAM_COUNTS_100("NetworkActionPredictor.Confidence_" +
+                             prerender::GetOmniboxHistogramSuffix(),
+                             confidence * 100);
+  }
 
   // Map the confidence to an action.
   Action action = ACTION_NONE;
   for (int i = 0; i < LAST_PREDICT_ACTION; ++i) {
     if (confidence >= kConfidenceCutoff[i]) {
       action = static_cast<Action>(i);
       break;
     }
   }
 
@@ skipping 212 matching lines @@
     return false;
 
   history::URLDatabase* url_db = service->InMemoryDatabase();
   if (!url_db)
     return false;
 
   DeleteOldEntries(url_db);
   return true;
 }
 
-double NetworkActionPredictor::ExactAlgorithm(
+double NetworkActionPredictor::CalculateConfidence(
     const string16& user_text,
-    const AutocompleteMatch& match) const {
+    const AutocompleteMatch& match,
+    bool* is_in_db) const {
   const DBCacheKey key = { user_text, match.destination_url };
 
+  *is_in_db = false;
   if (user_text.length() < kMinimumUserTextLength)
     return 0.0;
 
   const DBCacheMap::const_iterator iter = db_cache_.find(key);
   if (iter == db_cache_.end())
     return 0.0;
 
+  *is_in_db = true;
   const DBCacheValue& value = iter->second;
   if (value.number_of_hits < kMinimumNumberOfHits)
     return 0.0;
 
   return static_cast<double>(value.number_of_hits) /
       (value.number_of_hits + value.number_of_misses);
 }
 
 void NetworkActionPredictor::AddRow(
     const DBCacheKey& key,
@@ skipping 67 matching lines @@
 
   content::BrowserThread::PostTask(content::BrowserThread::DB, FROM_HERE,
       base::Bind(&NetworkActionPredictorDatabase::CommitTransaction, db_));
 }
 
 NetworkActionPredictor::TransitionalMatch::TransitionalMatch() {
 }
 
 NetworkActionPredictor::TransitionalMatch::~TransitionalMatch() {
 }