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