chromium/components/assist_ranker/example_preprocessing.h

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_ASSIST_RANKER_EXAMPLE_PREPROCESSING_H_
#define COMPONENTS_ASSIST_RANKER_EXAMPLE_PREPROCESSING_H_

#include "components/assist_ranker/proto/example_preprocessor.pb.h"
#include "components/assist_ranker/proto/ranker_example.pb.h"
#include "third_party/protobuf/src/google/protobuf/map.h"

namespace assist_ranker {

// Preprocessor for preprocessing RankerExample into formats that is needed by
// Ranker Predictors.
class ExamplePreprocessor { … };

// An iterator that goes through all features of a RankerExample and converts
// each field as a struct Field{full_name, value, error}.
//   (1) A numeric feature (bool_value, int32_value, float_value) is converted
//       to {feature_name, float(original_value), kSuccess}.
//   (2) A string feature is converted to
//       {feature_name_string_value, 1.0, kSuccess}.
//   (3) A string_value from a string list feature is converted to
//       {feature_name_string_value, 1.0, error_code} where non-empty list
//       gets error_code kSuccess, empty list gets kInvalidFeatureListIndex.
// Example:
//   std::vector<float> ExampleToStdFloat(const RankerExample& example,
//                                        const Map& feature_indices) {
//     std::vector<float> vectorized(feature_indices.size());
//     for (const auto& field : ExampleFloatIterator(example)) {
//       if (field.error == ExamplePreprocessor::kSuccess) {
//         const int index = feature_indices[field.fullname];
//         vectorized[index] = field.value;
//       }
//     }
//     return vectorized;
//   }
class ExampleFloatIterator { … };

}  // namespace assist_ranker

#endif  // COMPONENTS_ASSIST_RANKER_EXAMPLE_PREPROCESSING_H_