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#ifndef _PRECOMPUTATION_H_
#define _PRECOMPUTATION_H_
#include <memory>
#include <unordered_map>
#include <unordered_set>
#include <tuple>
#include <vector>
#include <boost/filesystem.hpp>
#include <boost/functional/hash.hpp>
namespace fs = boost::filesystem;
using namespace std;
namespace extractor {
typedef boost::hash<vector<int>> VectorHash;
typedef unordered_map<vector<int>, vector<int>, VectorHash> Index;
class SuffixArray;
/**
* Data structure wrapping an index with all the occurrences of the most
* frequent discontiguous collocations in the source data.
*
* Let a, b, c be contiguous collocations. The index will contain an entry for
* every collocation of the form:
* - aXb, where a and b are frequent
* - aXbXc, where a and b are super-frequent and c is frequent or
* b and c are super-frequent and a is frequent.
*/
class Precomputation {
public:
// Constructs the index using the suffix array.
Precomputation(
shared_ptr<SuffixArray> suffix_array, int num_frequent_patterns,
int num_super_frequent_patterns, int max_rule_span,
int max_rule_symbols, int min_gap_size,
int max_frequent_phrase_len, int min_frequency);
virtual ~Precomputation();
void WriteBinary(const fs::path& filepath) const;
// Returns a reference to the index.
virtual const Index& GetCollocations() const;
static int FIRST_NONTERMINAL;
static int SECOND_NONTERMINAL;
protected:
Precomputation();
private:
// Finds the most frequent contiguous collocations.
vector<vector<int>> FindMostFrequentPatterns(
shared_ptr<SuffixArray> suffix_array, const vector<int>& data,
int num_frequent_patterns, int max_frequent_phrase_len,
int min_frequency);
// Given the locations of the frequent contiguous collocations in a sentence,
// it adds new entries to the index for each discontiguous collocation
// matching the criteria specified in the class description.
void AddCollocations(
const vector<std::tuple<int, int, int>>& matchings, const vector<int>& data,
int max_rule_span, int min_gap_size, int max_rule_symbols);
// Adds an occurrence of a binary collocation.
void AddStartPositions(vector<int>& positions, int pos1, int pos2);
// Adds an occurrence of a ternary collocation.
void AddStartPositions(vector<int>& positions, int pos1, int pos2, int pos3);
Index collocations;
};
} // namespace extractor
#endif
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