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/*
* Copyright (C) 2013, The Android Open Source Project
*
* 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 LATINIME_FORGETTING_CURVE_UTILS_H
#define LATINIME_FORGETTING_CURVE_UTILS_H
#include <vector>
#include "defines.h"
namespace latinime {
class DictionaryHeaderStructurePolicy;
// TODO: Check the elapsed time and decrease the probability depending on the time. Time field is
// required to introduced to each terminal PtNode and bigram entry.
// TODO: Quit using bigram probability to indicate the delta.
class ForgettingCurveUtils {
public:
class TimeKeeper {
public:
TimeKeeper() : mCurrentTime(0) {}
void setCurrentTime();
int peekCurrentTime() const { return mCurrentTime; };
private:
DISALLOW_COPY_AND_ASSIGN(TimeKeeper);
int mCurrentTime;
};
static const int MAX_UNIGRAM_COUNT;
static const int MAX_UNIGRAM_COUNT_AFTER_GC;
static const int MAX_BIGRAM_COUNT;
static const int MAX_BIGRAM_COUNT_AFTER_GC;
static TimeKeeper sTimeKeeper;
static int getProbability(const int encodedUnigramProbability,
const int encodedBigramProbability);
static int getUpdatedEncodedProbability(const int originalEncodedProbability,
const int newProbability);
static int isValidEncodedProbability(const int encodedProbability);
static int getEncodedProbabilityToSave(const int encodedProbability,
const DictionaryHeaderStructurePolicy *const headerPolicy);
static bool needsToDecay(const bool mindsBlockByDecay, const int unigramCount,
const int bigramCount, const DictionaryHeaderStructurePolicy *const headerPolicy);
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(ForgettingCurveUtils);
class ProbabilityTable {
public:
ProbabilityTable();
int getProbability(const int encodedProbability) const {
if (encodedProbability < 0 || encodedProbability > static_cast<int>(mTable.size())) {
return NOT_A_PROBABILITY;
}
return mTable[encodedProbability];
}
private:
DISALLOW_COPY_AND_ASSIGN(ProbabilityTable);
std::vector<int> mTable;
};
static const int MAX_COMPUTED_PROBABILITY;
static const int MAX_ENCODED_PROBABILITY;
static const int MIN_VALID_ENCODED_PROBABILITY;
static const int ENCODED_PROBABILITY_STEP;
static const float MIN_PROBABILITY_TO_DECAY;
static const int DECAY_INTERVAL_SECONDS;
static const ProbabilityTable sProbabilityTable;
static int decodeProbability(const int encodedProbability);
static int backoff(const int unigramProbability);
};
} // namespace latinime
#endif /* LATINIME_FORGETTING_CURVE_UTILS_H */