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// Copyright 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.!
#ifndef MODEL_INTERFACE_H_
#define MODEL_INTERFACE_H_
#include <memory>
#include <set>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
#include "common.h"
#include "sentencepiece_processor.h"
#include "third_party/absl/strings/string_view.h"
#include "third_party/darts_clone/darts.h"
#include "util.h"
namespace sentencepiece {
// "_this_is_a_pen" => ["_this", "_is", "_a", "_pen"]
std::vector<absl::string_view> SplitIntoWords(absl::string_view text);
using EncodeResult = std::vector<std::pair<absl::string_view, int>>;
using NBestEncodeResult = std::vector<std::pair<EncodeResult, float>>;
class ModelProto;
// Given a list of strings, finds the longest string which is a
// prefix of a query.
class PrefixMatcher {
public:
// Initializes the PrefixMatcher with `dic`.
explicit PrefixMatcher(const std::set<absl::string_view> &dic);
// Finds the longest string in dic, which is a prefix of `w`.
// Returns the UTF8 byte length of matched string.
// `found` is set if a prefix match exists.
// If no entry is found, consumes one Unicode character.
int PrefixMatch(absl::string_view w, bool *found = nullptr) const;
// Replaces entries in `w` with `out`.
std::string GlobalReplace(absl::string_view w, absl::string_view out) const;
private:
std::unique_ptr<Darts::DoubleArray> trie_;
};
// Underlying model interface.
// Given a normalized string, returns a sequence of sentence pieces with ids.
class ModelInterface {
public:
using PieceToIdMap =
std::unordered_map<absl::string_view, int, string_util::string_view_hash>;
static const char *kUNK();
static const char *kBOS();
static const char *kEOS();
static const char *kPAD();
// `model_proto` should not be deleted until ModelInterface is destroyed.
explicit ModelInterface(const ModelProto &model_proto);
ModelInterface() {}
virtual ~ModelInterface();
// Returns Status.
// Encode/Decode functions are valid only when status is OK.
virtual util::Status status() const { return status_; }
virtual const ModelProto &model_proto() const { return *model_proto_; }
// Given a normalized string, returns a sequence of sentence pieces with ids.
// The concatenation of pieces must be the same as `normalized`.
virtual EncodeResult Encode(absl::string_view normalized) const = 0;
// The same as above, but returns nbest result with score.
virtual NBestEncodeResult NBestEncode(absl::string_view normalized,
int nbest_size) const {
LOG(ERROR) << "Not implemented.";
return NBestEncodeResult();
}
virtual EncodeResult SampleEncode(absl::string_view normalized,
float alpha) const {
LOG(ERROR) << "Not implemented.";
return EncodeResult();
}
// Returns the size of sentence pieces, which is the same
// as the size of vocabulary for NMT.
virtual int GetPieceSize() const;
// Returns the vocab id of `piece`.
// Returns UNK(0) if `piece` is unknown
virtual int PieceToId(absl::string_view piece) const;
// Returns the string representation of vocab with `id`.
// id must be 0 <= id < GetPieceSize().
virtual std::string IdToPiece(int id) const;
// Returns the score of `id`.
// Score represents a log probability of the piece.
// We can roughly estimate the unigram frequency of the piece.
virtual float GetScore(int id) const;
// Returns true if `id` is unknown symbol.
virtual bool IsUnknown(int id) const;
// Returns true if `id` is control symbol.
virtual bool IsControl(int id) const;
// Returns true if `id` is unused symbol.
virtual bool IsUnused(int id) const;
// Returns true if `id` is user defined symbol.
virtual bool IsUserDefined(int id) const;
protected:
void InitializePieces(bool use_prefix_matcher);
const ModelProto *model_proto_ = nullptr;
// PrefixMatcher for user defined symbols.
std::unique_ptr<PrefixMatcher> matcher_;
// piece -> id map for normal pieces
PieceToIdMap pieces_;
// piece -> id map for control and unknown
PieceToIdMap reserved_id_map_;
// unknown id.
int unk_id_ = 0;
// status.
util::Status status_;
};
} // namespace sentencepiece
#endif // MODEL_INTERFACE_H_
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