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// 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 "base/i18n/case_conversion.h"
#include "base/metrics/histogram.h"
#include "base/string_util.h"
#include "base/utf_string_conversions.h"
#include "chrome/browser/autocomplete/autocomplete_match.h"
#include "chrome/browser/history/history.h"
#include "chrome/browser/history/in_memory_database.h"
#include "chrome/browser/prerender/prerender_field_trial.h"
#include "chrome/browser/profiles/profile.h"
namespace {
const float kConfidenceCutoff[] = {
0.8f,
0.5f
};
COMPILE_ASSERT(arraysize(kConfidenceCutoff) ==
NetworkActionPredictor::LAST_PREDICT_ACTION,
ConfidenceCutoff_count_mismatch);
double OriginalAlgorithm(const history::URLRow& url_row) {
const double base_score = 1.0;
// This constant is ln(1/0.65) so we end up decaying to 65% of the base score
// for each week that passes.
const double kLnDecayPercent = 0.43078291609245;
base::TimeDelta time_passed = base::Time::Now() - url_row.last_visit();
// Clamp to 0.
const double decay_exponent = std::max(0.0,
kLnDecayPercent * static_cast<double>(time_passed.InMicroseconds()) /
base::Time::kMicrosecondsPerWeek);
const double kMaxDecaySpeedDivisor = 5.0;
const double kNumUsesPerDecaySpeedDivisorIncrement = 2.0;
const double decay_divisor = std::min(kMaxDecaySpeedDivisor,
(url_row.typed_count() + kNumUsesPerDecaySpeedDivisorIncrement - 1) /
kNumUsesPerDecaySpeedDivisorIncrement);
return base_score / exp(decay_exponent / decay_divisor);
}
double ConservativeAlgorithm(const history::URLRow& url_row) {
const double normalized_typed_count =
std::min(url_row.typed_count() / 5.0, 1.0);
const double base_score = atan(10 * normalized_typed_count) / atan(10.0);
// This constant is ln(1/0.65) so we end up decaying to 65% of the base score
// for each week that passes.
const double kLnDecayPercent = 0.43078291609245;
base::TimeDelta time_passed = base::Time::Now() - url_row.last_visit();
const double decay_exponent = std::max(0.0,
kLnDecayPercent * static_cast<double>(time_passed.InMicroseconds()) /
base::Time::kMicrosecondsPerWeek);
return base_score / exp(decay_exponent);
}
bool GetURLRowForAutocompleteMatch(Profile* profile,
const AutocompleteMatch& match,
history::URLRow* url_row) {
DCHECK(url_row);
HistoryService* history_service =
profile->GetHistoryService(Profile::EXPLICIT_ACCESS);
if (!history_service)
return false;
history::URLDatabase* url_db = history_service->InMemoryDatabase();
return url_db && (url_db->GetRowForURL(match.destination_url, url_row) != 0);
}
}
NetworkActionPredictor::NetworkActionPredictor(Profile* profile)
: profile_(profile) {
}
NetworkActionPredictor::~NetworkActionPredictor() {
}
// Given a match, return a recommended action.
NetworkActionPredictor::Action NetworkActionPredictor::RecommendAction(
const string16& user_text,
const AutocompleteMatch& match) const {
double confidence = 0.0;
switch (prerender::GetOmniboxHeuristicToUse()) {
case prerender::OMNIBOX_HEURISTIC_ORIGINAL: {
history::URLRow url_row;
if (GetURLRowForAutocompleteMatch(profile_, match, &url_row))
confidence = OriginalAlgorithm(url_row);
break;
}
case prerender::OMNIBOX_HEURISTIC_CONSERVATIVE: {
history::URLRow url_row;
if (GetURLRowForAutocompleteMatch(profile_, match, &url_row))
confidence = ConservativeAlgorithm(url_row);
break;
}
default:
NOTREACHED();
break;
};
CHECK(confidence >= 0.0 && confidence <= 1.0);
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;
}
}
// Downgrade prerender to preconnect if this is a search match.
if (action == ACTION_PRERENDER &&
(match.type == AutocompleteMatch::SEARCH_WHAT_YOU_TYPED ||
match.type == AutocompleteMatch::SEARCH_SUGGEST ||
match.type == AutocompleteMatch::SEARCH_OTHER_ENGINE)) {
action = ACTION_PRECONNECT;
}
return action;
}
// Return true if the suggestion type warrants a TCP/IP preconnection.
// i.e., it is now quite likely that the user will select the related domain.
// static
bool NetworkActionPredictor::IsPreconnectable(const AutocompleteMatch& match) {
switch (match.type) {
// Matches using the user's default search engine.
case AutocompleteMatch::SEARCH_WHAT_YOU_TYPED:
case AutocompleteMatch::SEARCH_HISTORY:
case AutocompleteMatch::SEARCH_SUGGEST:
// A match that uses a non-default search engine (e.g. for tab-to-search).
case AutocompleteMatch::SEARCH_OTHER_ENGINE:
return true;
default:
return false;
}
}
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