1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef LIBTEXTCLASSIFIER_CACHED_FEATURES_H_
18 #define LIBTEXTCLASSIFIER_CACHED_FEATURES_H_
19 
20 #include <memory>
21 #include <vector>
22 
23 #include "model-executor.h"
24 #include "model_generated.h"
25 #include "types.h"
26 
27 namespace libtextclassifier2 {
28 
29 // Holds state for extracting features across multiple calls and reusing them.
30 // Assumes that features for each Token are independent.
31 class CachedFeatures {
32  public:
33   static std::unique_ptr<CachedFeatures> Create(
34       const TokenSpan& extraction_span,
35       std::unique_ptr<std::vector<float>> features,
36       std::unique_ptr<std::vector<float>> padding_features,
37       const FeatureProcessorOptions* options, int feature_vector_size);
38 
39   // Appends the click context features for the given click position to
40   // 'output_features'.
41   void AppendClickContextFeaturesForClick(
42       int click_pos, std::vector<float>* output_features) const;
43 
44   // Appends the bounds-sensitive features for the given token span to
45   // 'output_features'.
46   void AppendBoundsSensitiveFeaturesForSpan(
47       TokenSpan selected_span, std::vector<float>* output_features) const;
48 
49   // Returns number of features that 'AppendFeaturesForSpan' appends.
OutputFeaturesSize()50   int OutputFeaturesSize() const { return output_features_size_; }
51 
52  private:
CachedFeatures()53   CachedFeatures() {}
54 
55   // Appends token features to the output. The intended_span specifies which
56   // tokens' features should be used in principle. The read_mask_span restricts
57   // which tokens are actually read. For tokens outside of the read_mask_span,
58   // padding tokens are used instead.
59   void AppendFeaturesInternal(const TokenSpan& intended_span,
60                               const TokenSpan& read_mask_span,
61                               std::vector<float>* output_features) const;
62 
63   // Appends features of one padding token to the output.
64   void AppendPaddingFeatures(std::vector<float>* output_features) const;
65 
66   // Appends the features of tokens from the given span to the output. The
67   // features are averaged so that the appended features have the size
68   // corresponding to one token.
69   void AppendBagFeatures(const TokenSpan& bag_span,
70                          std::vector<float>* output_features) const;
71 
72   int NumFeaturesPerToken() const;
73 
74   TokenSpan extraction_span_;
75   const FeatureProcessorOptions* options_;
76   int output_features_size_;
77   std::unique_ptr<std::vector<float>> features_;
78   std::unique_ptr<std::vector<float>> padding_features_;
79 };
80 
81 }  // namespace libtextclassifier2
82 
83 #endif  // LIBTEXTCLASSIFIER_CACHED_FEATURES_H_
84