78 lines
3.0 KiB
C++
78 lines
3.0 KiB
C++
/*
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* Copyright (C) 2014, 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 LATINIME_DYNAMIC_LANGUAGE_MODEL_PROBABILITY_UTILS_H
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#define LATINIME_DYNAMIC_LANGUAGE_MODEL_PROBABILITY_UTILS_H
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#include <algorithm>
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#include "defines.h"
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#include "suggest/core/dictionary/property/historical_info.h"
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#include "utils/ngram_utils.h"
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#include "utils/time_keeper.h"
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namespace latinime {
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class DynamicLanguageModelProbabilityUtils {
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public:
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static float computeRawProbabilityFromCounts(const int count, const int contextCount,
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const NgramType ngramType) {
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const int minCount = ASSUMED_MIN_COUNTS[static_cast<int>(ngramType)];
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return static_cast<float>(count) / static_cast<float>(std::max(contextCount, minCount));
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}
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static float backoff(const int ngramProbability, const NgramType ngramType) {
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const int probability =
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ngramProbability + ENCODED_BACKOFF_WEIGHTS[static_cast<int>(ngramType)];
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return std::min(std::max(probability, NOT_A_PROBABILITY), MAX_PROBABILITY);
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}
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static int getDecayedProbability(const int probability, const HistoricalInfo historicalInfo) {
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const int elapsedTime = TimeKeeper::peekCurrentTime() - historicalInfo.getTimestamp();
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if (elapsedTime < 0) {
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AKLOGE("The elapsed time is negatime value. Timestamp overflow?");
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return NOT_A_PROBABILITY;
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}
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// TODO: Improve this logic.
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// We don't modify probability depending on the elapsed time.
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return probability;
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}
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static int shouldRemoveEntryDuringGC(const HistoricalInfo historicalInfo) {
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// TODO: Improve this logic.
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const int elapsedTime = TimeKeeper::peekCurrentTime() - historicalInfo.getTimestamp();
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return elapsedTime > DURATION_TO_DISCARD_ENTRY_IN_SECONDS;
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}
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static int getPriorityToPreventFromEviction(const HistoricalInfo historicalInfo) {
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// TODO: Improve this logic.
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// More recently input entries get higher priority.
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return historicalInfo.getTimestamp();
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}
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private:
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DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicLanguageModelProbabilityUtils);
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static_assert(MAX_PREV_WORD_COUNT_FOR_N_GRAM <= 2, "Max supported Ngram is Trigram.");
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static const int ASSUMED_MIN_COUNTS[];
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static const int ENCODED_BACKOFF_WEIGHTS[];
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static const int DURATION_TO_DISCARD_ENTRY_IN_SECONDS;
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};
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} // namespace latinime
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#endif /* LATINIME_DYNAMIC_LANGUAGE_MODEL_PROBABILITY_UTILS_H */
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