101 lines
4.3 KiB
C++
101 lines
4.3 KiB
C++
/*
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* Copyright (C) 2013, 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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#include "dictionary/utils/multi_bigram_map.h"
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#include <cstddef>
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#include <unordered_map>
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namespace latinime {
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// Max number of bigram maps (previous word contexts) to be cached. Increasing this number
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// could improve bigram lookup speed for multi-word suggestions, but at the cost of more memory
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// usage. Also, there are diminishing returns since the most frequently used bigrams are
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// typically near the beginning of the input and are thus the first ones to be cached. Note
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// that these bigrams are reset for each new composing word.
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const size_t MultiBigramMap::MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP = 25;
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// Most common previous word contexts currently have 100 bigrams
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const int MultiBigramMap::BigramMap::DEFAULT_HASH_MAP_SIZE_FOR_EACH_BIGRAM_MAP = 100;
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// Look up the bigram probability for the given word pair from the cached bigram maps.
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// Also caches the bigrams if there is space remaining and they have not been cached already.
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int MultiBigramMap::getBigramProbability(
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const DictionaryStructureWithBufferPolicy *const structurePolicy,
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const WordIdArrayView prevWordIds, const int nextWordId,
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const int unigramProbability) {
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if (prevWordIds.empty() || prevWordIds[0] == NOT_A_WORD_ID) {
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return structurePolicy->getProbability(unigramProbability, NOT_A_PROBABILITY);
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}
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const auto mapPosition = mBigramMaps.find(prevWordIds[0]);
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if (mapPosition != mBigramMaps.end()) {
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return mapPosition->second.getBigramProbability(structurePolicy, nextWordId,
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unigramProbability);
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}
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if (mBigramMaps.size() < MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP) {
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addBigramsForWord(structurePolicy, prevWordIds);
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return mBigramMaps[prevWordIds[0]].getBigramProbability(structurePolicy,
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nextWordId, unigramProbability);
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}
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return readBigramProbabilityFromBinaryDictionary(structurePolicy, prevWordIds,
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nextWordId, unigramProbability);
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}
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void MultiBigramMap::BigramMap::init(
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const DictionaryStructureWithBufferPolicy *const structurePolicy,
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const WordIdArrayView prevWordIds) {
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structurePolicy->iterateNgramEntries(prevWordIds, this /* listener */);
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}
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int MultiBigramMap::BigramMap::getBigramProbability(
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const DictionaryStructureWithBufferPolicy *const structurePolicy,
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const int nextWordId, const int unigramProbability) const {
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int bigramProbability = NOT_A_PROBABILITY;
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if (mBloomFilter.isInFilter(nextWordId)) {
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const auto bigramProbabilityIt = mBigramMap.find(nextWordId);
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if (bigramProbabilityIt != mBigramMap.end()) {
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bigramProbability = bigramProbabilityIt->second;
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}
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}
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return structurePolicy->getProbability(unigramProbability, bigramProbability);
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}
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void MultiBigramMap::BigramMap::onVisitEntry(const int ngramProbability, const int targetWordId) {
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if (targetWordId == NOT_A_WORD_ID) {
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return;
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}
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mBigramMap[targetWordId] = ngramProbability;
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mBloomFilter.setInFilter(targetWordId);
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}
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void MultiBigramMap::addBigramsForWord(
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const DictionaryStructureWithBufferPolicy *const structurePolicy,
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const WordIdArrayView prevWordIds) {
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mBigramMaps[prevWordIds[0]].init(structurePolicy, prevWordIds);
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}
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int MultiBigramMap::readBigramProbabilityFromBinaryDictionary(
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const DictionaryStructureWithBufferPolicy *const structurePolicy,
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const WordIdArrayView prevWordIds, const int nextWordId, const int unigramProbability) {
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const int bigramProbability = structurePolicy->getProbabilityOfWord(prevWordIds, nextWordId);
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if (bigramProbability != NOT_A_PROBABILITY) {
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return bigramProbability;
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}
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return structurePolicy->getProbability(unigramProbability, NOT_A_PROBABILITY);
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}
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} // namespace latinime
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