[translate] Add translate ranker model loader.

components/translate/core/browser/translate_ranker_impl.cc

Index: components/translate/core/browser/translate_ranker_impl.cc
diff --git a/components/translate/core/browser/translate_ranker_impl.cc b/components/translate/core/browser/translate_ranker_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ed4a9b1f2df21957ae73d17330d31d48db803f2c
--- /dev/null
+++ b/components/translate/core/browser/translate_ranker_impl.cc
@@ -0,0 +1,282 @@
+// Copyright 2016 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 "components/translate/core/browser/translate_ranker_impl.h"
+
+#include <cmath>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/command_line.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/profiler/scoped_tracker.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "base/task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "components/metrics/proto/translate_event.pb.h"
+#include "components/translate/core/browser/proto/ranker_model.pb.h"
+#include "components/translate/core/browser/proto/translate_ranker_model.pb.h"
+#include "components/translate/core/browser/ranker_model.h"
+#include "components/translate/core/browser/translate_download_manager.h"
+#include "components/translate/core/browser/translate_prefs.h"
+#include "components/translate/core/browser/translate_url_fetcher.h"
+#include "components/translate/core/common/translate_switches.h"
+#include "components/variations/variations_associated_data.h"
+#include "url/gurl.h"
+
+namespace translate {
+
+namespace {
+
+using chrome_intelligence::RankerModel;
+using chrome_intelligence::RankerModelProto;
+using chrome_intelligence::TranslateRankerModel;
+
+const double kTranslationOfferThreshold = 0.5;
+
+const char kTranslateRankerModelFileName[] = "Translate Ranker Model";
+const char kUmaPrefix[] = "Translate.Ranker";
+const char kUnknown[] = "UNKNOWN";
+
+double Sigmoid(double x) {
+  return 1.0 / (1.0 + exp(-x));
+}
+
+double SafeRatio(int numerator, int denominator) {
+  return denominator ? (numerator / static_cast<double>(denominator)) : 0.0;
+}
+
+double ScoreComponent(const google::protobuf::Map<std::string, float>& weights,
+                      const std::string& key) {
+  auto i = weights.find(base::ToLowerASCII(key));
+  if (i == weights.end())
+    i = weights.find(kUnknown);
+  return i == weights.end() ? 0.0 : i->second;
+}
+
+RankerModelStatus ValidateModel(const RankerModel& model) {
+  if (model.proto().model_case() != RankerModelProto::kTranslate)
+    return RankerModelStatus::VALIDATION_FAILED;
+
+  if (model.proto().translate().model_revision_case() !=
+      TranslateRankerModel::kLogisticRegressionModel) {
+    return RankerModelStatus::INCOMPATIBLE;
+  }
+
+  return RankerModelStatus::OK;
+}
+
+}  // namespace
+
+const base::Feature kTranslateRankerQuery{"TranslateRankerQuery",
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
+
+const base::Feature kTranslateRankerEnforcement{
+    "TranslateRankerEnforcement", base::FEATURE_DISABLED_BY_DEFAULT};
+
+const base::Feature kTranslateRankerLogging{"TranslateRankerLogging",
+                                            base::FEATURE_DISABLED_BY_DEFAULT};
+
+TranslateRankerFeatures::TranslateRankerFeatures() {}
+
+TranslateRankerFeatures::TranslateRankerFeatures(int accepted,
+                                                 int denied,
+                                                 int ignored,
+                                                 const std::string& src,
+                                                 const std::string& dst,
+                                                 const std::string& cntry,
+                                                 const std::string& locale)
+    : accepted_count(accepted),
+      denied_count(denied),
+      ignored_count(ignored),
+      total_count(accepted_count + denied_count + ignored_count),
+      src_lang(src),
+      dst_lang(dst),
+      country(cntry),
+      app_locale(locale),
+      accepted_ratio(SafeRatio(accepted_count, total_count)),
+      denied_ratio(SafeRatio(denied_count, total_count)),
+      ignored_ratio(SafeRatio(ignored_count, total_count)) {}
+
+TranslateRankerFeatures::TranslateRankerFeatures(const TranslatePrefs& prefs,
+                                                 const std::string& src,
+                                                 const std::string& dst,
+                                                 const std::string& locale)
+    : TranslateRankerFeatures(prefs.GetTranslationAcceptedCount(src),
+                              prefs.GetTranslationDeniedCount(src),
+                              prefs.GetTranslationIgnoredCount(src),
+                              src,
+                              dst,
+                              prefs.GetCountry(),
+                              locale) {}
+
+TranslateRankerFeatures::~TranslateRankerFeatures() {}
+
+void TranslateRankerFeatures::WriteTo(std::ostream& stream) const {
+  stream << "src_lang='" << src_lang << "', "
+         << "dst_lang='" << dst_lang << "', "
+         << "country='" << country << "', "
+         << "app_locale='" << app_locale << "', "
+         << "accept_count=" << accepted_count << ", "
+         << "denied_count=" << denied_count << ", "
+         << "ignored_count=" << ignored_count << ", "
+         << "total_count=" << total_count << ", "
+         << "accept_ratio=" << accepted_ratio << ", "
+         << "decline_ratio=" << denied_ratio << ", "
+         << "ignore_ratio=" << ignored_ratio;
+}
+
+TranslateRankerImpl::TranslateRankerImpl(const base::FilePath& model_path,
+                                         const GURL& model_url)
+    : weak_ptr_factory_(this) {
+  model_loader_ = base::MakeUnique<RankerModelLoader>(
+      base::Bind(&ValidateModel),
+      base::Bind(&TranslateRankerImpl::OnModelAvailable,
+                 weak_ptr_factory_.GetWeakPtr()),
+      model_path, model_url, kUmaPrefix);
+  model_loader_->Start();
+}
+
+TranslateRankerImpl::~TranslateRankerImpl() {}
+
+// static
+base::FilePath TranslateRankerImpl::GetModelPath(
+    const base::FilePath& data_dir) {
+  if (data_dir.empty())
+    return base::FilePath();
+
+  // Otherwise, look for the file in data dir.
+  return data_dir.AppendASCII(kTranslateRankerModelFileName);
+}
+
+// static
+GURL TranslateRankerImpl::GetModelURL() {
+  // Allow override of the ranker model URL from the command line.
+  std::string raw_url;
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kTranslateRankerModelURL)) {
+    raw_url =
+        command_line->GetSwitchValueASCII(switches::kTranslateRankerModelURL);
+  } else {
+    // Otherwise take the ranker model URL from the ranker query variation.
+    raw_url = variations::GetVariationParamValueByFeature(
+        kTranslateRankerQuery, switches::kTranslateRankerModelURL);
+  }
+
+  DVLOG(3) << switches::kTranslateRankerModelURL << " = " << raw_url;
+
+  return GURL(raw_url);
+}
+
+bool TranslateRankerImpl::IsLoggingEnabled() {
+  return base::FeatureList::IsEnabled(kTranslateRankerLogging);
+}
+
+bool TranslateRankerImpl::IsQueryEnabled() {
+  return base::FeatureList::IsEnabled(kTranslateRankerQuery);
+}
+
+bool TranslateRankerImpl::IsEnforcementEnabled() {
+  return base::FeatureList::IsEnabled(kTranslateRankerEnforcement);
+}
+
+int TranslateRankerImpl::GetModelVersion() const {
+  return model_ ? model_->proto().translate().version() : 0;
+}
+
+bool TranslateRankerImpl::ShouldOfferTranslation(
+    const TranslatePrefs& translate_prefs,
+    const std::string& src_lang,
+    const std::string& dst_lang) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
+  // The ranker is a gate in the "show a translation prompt" flow. To retain
+  // the pre-existing functionality, it defaults to returning true in the
+  // absence of a model or if enforcement is disabled. As this is ranker is
+  // subsumed into a more general assist ranker, this default will go away
+  // (or become False).
+  const bool kDefaultResponse = true;
+
+  // If we don't have a model, request one and return the default.
+  if (model_ == nullptr) {
+    return kDefaultResponse;
+  }
+
+  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.ShouldOfferTranslation");
+
+  // TODO(rogerm): Remove ScopedTracker below once crbug.com/646711 is closed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "646711 translate::TranslateRankerImpl::ShouldOfferTranslation"));
+
+  TranslateRankerFeatures features(
+      translate_prefs, src_lang, dst_lang,
+      TranslateDownloadManager::GetInstance()->application_locale());
+
+  double score = CalculateScore(features);
+
+  DVLOG(2) << "TranslateRankerImpl::ShouldOfferTranslation: "
+           << "Score = " << score << ", Features=[" << features << "]";
+
+  bool result = (score >= kTranslationOfferThreshold);
+
+  UMA_HISTOGRAM_BOOLEAN("Translate.Ranker.QueryResult", result);
+
+  return result;
+}
+
+double TranslateRankerImpl::CalculateScore(
+    const TranslateRankerFeatures& features) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
+  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.CalculateScore");
+  DCHECK(model_ != nullptr);
+  const TranslateRankerModel::LogisticRegressionModel& logit =
+      model_->proto().translate().logistic_regression_model();
+
+  double dot_product =
+      (features.accepted_count * logit.accept_count_weight()) +
+      (features.denied_count * logit.decline_count_weight()) +
+      (features.ignored_count * logit.ignore_count_weight()) +
+      (features.accepted_ratio * logit.accept_ratio_weight()) +
+      (features.denied_ratio * logit.decline_ratio_weight()) +
+      (features.ignored_ratio * logit.ignore_ratio_weight()) +
+      ScoreComponent(logit.source_language_weight(), features.src_lang) +
+      ScoreComponent(logit.dest_language_weight(), features.dst_lang) +
+      ScoreComponent(logit.country_weight(), features.country) +
+      ScoreComponent(logit.locale_weight(), features.app_locale);
+
+  return Sigmoid(dot_product + logit.bias());
+}
+
+void TranslateRankerImpl::FlushTranslateEvents(
+    std::vector<metrics::TranslateEventProto>* events) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
+  DVLOG(3) << "Flushing translate ranker events.";
+  events->swap(event_cache_);
+  event_cache_.clear();
+}
+
+void TranslateRankerImpl::AddTranslateEvent(
+    const metrics::TranslateEventProto& event) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
+  DVLOG(3) << "Adding translate ranker event.";
+  if (IsLoggingEnabled())
+    event_cache_.push_back(event);
+}
+
+void TranslateRankerImpl::OnModelAvailable(std::unique_ptr<RankerModel> model) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
+  model_ = std::move(model);
+}
+
+}  // namespace translate
+
+std::ostream& operator<<(std::ostream& stream,
+                         const translate::TranslateRankerFeatures& features) {
+  features.WriteTo(stream);
+  return stream;
+}