[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..94a732a06a395859c705d2cb57e8ab4f54ff4df8
--- /dev/null
+++ b/components/translate/core/browser/translate_ranker_impl.cc
@@ -0,0 +1,270 @@
+// 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/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 {
+
+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 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;
+}
+
+}  // 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(const TranslatePrefs& prefs,
+                                                 const std::string& src,
+                                                 const std::string& dst,
+                                                 const std::string& locale)
+    : accepted_count(prefs.GetTranslationAcceptedCount(src)),
+      denied_count(prefs.GetTranslationDeniedCount(src)),
+      ignored_count(prefs.GetTranslationIgnoredCount(src)),
+      total_count(accepted_count + denied_count + ignored_count),
+      src_lang(src),
+      dst_lang(dst),
+      country(prefs.GetCountry()),
+      app_locale(locale),
+      accepted_ratio(total_count ? (accepted_count / total_count) : 0.0),
+      denied_ratio(total_count ? (denied_count / total_count) : 0.0),
+      ignored_ratio(total_count ? (ignored_count / total_count) : 0.0) {}
+
+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)
+    : task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      model_loader_(this, model_path, model_url, kUmaPrefix) {
+  model_loader_.Start();
+}
+
+TranslateRankerImpl::~TranslateRankerImpl() {}
+
+// static
+base::FilePath TranslateRankerImpl::GetModelPath(
+    const base::FilePath& data_dir) {
+  // Allow override of the ranker model path from the command line.
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kTranslateRankerModelPath)) {
+    return base::FilePath(command_line->GetSwitchValueNative(
+        switches::kTranslateRankerModelPath));
+  }
+
+  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.
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kTranslateRankerModelURL)) {
+    return GURL(
+        command_line->GetSwitchValueASCII(switches::kTranslateRankerModelURL));
+  }
+
+  // Otherwise take the ranker model URL from the ranker query variation.
+  const std::string raw_url = variations::GetVariationParamValueByFeature(
+      kTranslateRankerQuery, switches::kTranslateRankerModelURL);
+
+  DVLOG(3) << switches::kTranslateRankerModelURL << " = " << raw_url;
+
+  return GURL(raw_url);
+}
+
+bool TranslateRankerImpl::IsEnabled() {
+  return IsQueryEnabled() || IsEnforcementEnabled();
+}
+
+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_->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 chrome_intelligence::TranslateRankerModel::LogisticRegressionModel&
+      logit = model_->translate().v1();
+
+  double dot_product =
+      (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<std::unique_ptr<metrics::TranslateEventProto>>* events) {
+  events->swap(event_cache_);
+  event_cache_.clear();
+}
+
+void TranslateRankerImpl::AddTranslateEvent(
+    std::unique_ptr<metrics::TranslateEventProto> event) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
+  if (IsLoggingEnabled())
+    event_cache_.push_back(std::move(event));
+}
+
+RankerModelStatus TranslateRankerImpl::Validate(
+    const chrome_intelligence::RankerModel& model) const {
+  if (model.model_type_case() != chrome_intelligence::RankerModel::kTranslate)
+    return RankerModelStatus::VALIDATION_FAILED;
+
+  if (model.translate().model_iteration_case() !=
+      chrome_intelligence::TranslateRankerModel::kV1) {
+    return RankerModelStatus::INCOMPATIBLE;
+  }
+
+  return RankerModelStatus::OK;
+}
+
+void TranslateRankerImpl::OnModelAvailable(
+    std::unique_ptr<chrome_intelligence::RankerModel> model) {
+  // Move ownership of |model| to this translate ranker, but be sure to do so
+  // on using this ranker's task runner to avoid threading issues.
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&TranslateRankerImpl::OnModelAvailableImpl,
+                 base::Unretained(this), base::Passed(std::move(model))));
+}
+
+void TranslateRankerImpl::OnModelAvailableImpl(
+    std::unique_ptr<chrome_intelligence::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;
+}