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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_MULTI_BIGRAM_MAP_H
#define LATINIME_MULTI_BIGRAM_MAP_H
#include <cstddef>
#include <unordered_map>
#include "defines.h"
#include "dictionary/interface/dictionary_structure_with_buffer_policy.h"
#include "dictionary/interface/ngram_listener.h"
#include "dictionary/utils/binary_dictionary_bigrams_iterator.h"
#include "dictionary/utils/bloom_filter.h"
#include "utils/int_array_view.h"
namespace latinime {
// Class for caching bigram maps for multiple previous word contexts. This is useful since the
// algorithm needs to look up the set of bigrams for every word pair that occurs in every
// multi-word suggestion.
class MultiBigramMap {
public:
MultiBigramMap() : mBigramMaps() {}
~MultiBigramMap() {}
// 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 getBigramProbability(const DictionaryStructureWithBufferPolicy *const structurePolicy,
const WordIdArrayView prevWordIds, const int nextWordId, const int unigramProbability);
void clear() {
mBigramMaps.clear();
}
private:
DISALLOW_COPY_AND_ASSIGN(MultiBigramMap);
class BigramMap : public NgramListener {
public:
BigramMap() : mBigramMap(DEFAULT_HASH_MAP_SIZE_FOR_EACH_BIGRAM_MAP), mBloomFilter() {}
// Copy constructor needed for std::unordered_map.
BigramMap(const BigramMap &bigramMap)
: mBigramMap(bigramMap.mBigramMap), mBloomFilter(bigramMap.mBloomFilter) {}
virtual ~BigramMap() {}
void init(const DictionaryStructureWithBufferPolicy *const structurePolicy,
const WordIdArrayView prevWordIds);
int getBigramProbability(
const DictionaryStructureWithBufferPolicy *const structurePolicy,
const int nextWordId, const int unigramProbability) const;
virtual void onVisitEntry(const int ngramProbability, const int targetWordId);
private:
static const int DEFAULT_HASH_MAP_SIZE_FOR_EACH_BIGRAM_MAP;
std::unordered_map<int, int> mBigramMap;
BloomFilter mBloomFilter;
};
void addBigramsForWord(const DictionaryStructureWithBufferPolicy *const structurePolicy,
const WordIdArrayView prevWordIds);
int readBigramProbabilityFromBinaryDictionary(
const DictionaryStructureWithBufferPolicy *const structurePolicy,
const WordIdArrayView prevWordIds, const int nextWordId, const int unigramProbability);
static const size_t MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP;
std::unordered_map<int, BigramMap> mBigramMaps;
};
} // namespace latinime
#endif // LATINIME_MULTI_BIGRAM_MAP_H
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