103 lines
3.4 KiB
C++
103 lines
3.4 KiB
C++
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LIBTEXTCLASSIFIER_SMARTSELECT_TOKEN_FEATURE_EXTRACTOR_H_
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#define LIBTEXTCLASSIFIER_SMARTSELECT_TOKEN_FEATURE_EXTRACTOR_H_
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#include <memory>
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#include <vector>
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#include "base.h"
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#include "smartselect/types.h"
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#include "util/strings/stringpiece.h"
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#include "unicode/regex.h"
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namespace libtextclassifier {
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struct TokenFeatureExtractorOptions {
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// Number of buckets used for hashing charactergrams.
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int num_buckets = 0;
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// Orders of charactergrams to extract. E.g., 2 means character bigrams, 3
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// character trigrams etc.
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std::vector<int> chargram_orders;
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// Whether to extract the token case feature.
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bool extract_case_feature = false;
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// If true, will use the unicode-aware functionality for extracting features.
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bool unicode_aware_features = false;
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// Whether to extract the selection mask feature.
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bool extract_selection_mask_feature = false;
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// Regexp features to extract.
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std::vector<std::string> regexp_features;
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// Whether to remap digits to a single number.
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bool remap_digits = false;
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// Whether to lowercase all tokens.
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bool lowercase_tokens = false;
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// Maximum length of a word.
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int max_word_length = 20;
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};
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class TokenFeatureExtractor {
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public:
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explicit TokenFeatureExtractor(const TokenFeatureExtractorOptions& options);
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// Extracts features from a token.
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// - is_in_span is a bool indicator whether the token is a part of the
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// selection span (true) or not (false).
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// - sparse_features are indices into a sparse feature vector of size
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// options.num_buckets which are set to 1.0 (others are implicitly 0.0).
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// - dense_features are values of a dense feature vector of size 0-2
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// (depending on the options) for the token
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bool Extract(const Token& token, bool is_in_span,
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std::vector<int>* sparse_features,
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std::vector<float>* dense_features) const;
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int DenseFeaturesCount() const {
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return options_.extract_case_feature +
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options_.extract_selection_mask_feature + regex_patterns_.size();
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}
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protected:
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// Hashes given token to given number of buckets.
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int HashToken(StringPiece token) const;
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// Extracts the charactergram features from the token.
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std::vector<int> ExtractCharactergramFeatures(const Token& token) const;
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// Extracts the charactergram features from the token in a non-unicode-aware
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// way.
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std::vector<int> ExtractCharactergramFeaturesAscii(const Token& token) const;
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// Extracts the charactergram features from the token in a unicode-aware way.
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std::vector<int> ExtractCharactergramFeaturesUnicode(
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const Token& token) const;
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private:
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TokenFeatureExtractorOptions options_;
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std::vector<std::unique_ptr<icu::RegexPattern>> regex_patterns_;
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};
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} // namespace libtextclassifier
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#endif // LIBTEXTCLASSIFIER_SMARTSELECT_TOKEN_FEATURE_EXTRACTOR_H_
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