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#include "fast_intersector.h"
#include <cassert>
#include "data_array.h"
#include "phrase.h"
#include "phrase_location.h"
#include "precomputation.h"
#include "suffix_array.h"
#include "vocabulary.h"
namespace extractor {
FastIntersector::FastIntersector(shared_ptr<SuffixArray> suffix_array,
shared_ptr<Precomputation> precomputation,
shared_ptr<Vocabulary> vocabulary,
int max_rule_span,
int min_gap_size) :
suffix_array(suffix_array),
vocabulary(vocabulary),
max_rule_span(max_rule_span),
min_gap_size(min_gap_size) {
Index precomputed_collocations = precomputation->GetCollocations();
for (pair<vector<int>, vector<int>> entry: precomputed_collocations) {
vector<int> phrase = ConvertPhrase(entry.first);
collocations[phrase] = entry.second;
}
}
FastIntersector::FastIntersector() {}
FastIntersector::~FastIntersector() {}
vector<int> FastIntersector::ConvertPhrase(const vector<int>& old_phrase) {
vector<int> new_phrase;
new_phrase.reserve(old_phrase.size());
shared_ptr<DataArray> data_array = suffix_array->GetData();
for (int word_id: old_phrase) {
if (word_id < 0) {
new_phrase.push_back(word_id);
} else {
new_phrase.push_back(
vocabulary->GetTerminalIndex(data_array->GetWord(word_id)));
}
}
return new_phrase;
}
PhraseLocation FastIntersector::Intersect(
PhraseLocation& prefix_location,
PhraseLocation& suffix_location,
const Phrase& phrase) {
vector<int> symbols = phrase.Get();
// We should never attempt to do an intersect query for a pattern starting or
// ending with a non terminal. The RuleFactory should handle these cases,
// initializing the matchings list with the one for the pattern without the
// starting or ending terminal.
assert(vocabulary->IsTerminal(symbols.front())
&& vocabulary->IsTerminal(symbols.back()));
if (collocations.count(symbols)) {
return PhraseLocation(collocations[symbols], phrase.Arity() + 1);
}
bool prefix_ends_with_x =
!vocabulary->IsTerminal(symbols[symbols.size() - 2]);
bool suffix_starts_with_x = !vocabulary->IsTerminal(symbols[1]);
if (EstimateNumOperations(prefix_location, prefix_ends_with_x) <=
EstimateNumOperations(suffix_location, suffix_starts_with_x)) {
return ExtendPrefixPhraseLocation(prefix_location, phrase,
prefix_ends_with_x, symbols.back());
} else {
return ExtendSuffixPhraseLocation(suffix_location, phrase,
suffix_starts_with_x, symbols.front());
}
}
int FastIntersector::EstimateNumOperations(
const PhraseLocation& phrase_location, bool has_margin_x) const {
int num_locations = phrase_location.GetSize();
return has_margin_x ? num_locations * max_rule_span : num_locations;
}
PhraseLocation FastIntersector::ExtendPrefixPhraseLocation(
PhraseLocation& prefix_location, const Phrase& phrase,
bool prefix_ends_with_x, int next_symbol) const {
ExtendPhraseLocation(prefix_location);
vector<int> positions = *prefix_location.matchings;
int num_subpatterns = prefix_location.num_subpatterns;
vector<int> new_positions;
shared_ptr<DataArray> data_array = suffix_array->GetData();
int data_array_symbol = data_array->GetWordId(
vocabulary->GetTerminalValue(next_symbol));
if (data_array_symbol == -1) {
return PhraseLocation(new_positions, num_subpatterns);
}
pair<int, int> range = GetSearchRange(prefix_ends_with_x);
for (size_t i = 0; i < positions.size(); i += num_subpatterns) {
int sent_id = data_array->GetSentenceId(positions[i]);
int sent_end = data_array->GetSentenceStart(sent_id + 1) - 1;
int pattern_end = positions[i + num_subpatterns - 1] + range.first;
if (prefix_ends_with_x) {
pattern_end += phrase.GetChunkLen(phrase.Arity() - 1) - 1;
} else {
pattern_end += phrase.GetChunkLen(phrase.Arity()) - 2;
}
// Searches for the last symbol in the phrase after each prefix occurrence.
for (int j = range.first; j < range.second; ++j) {
if (pattern_end >= sent_end ||
pattern_end - positions[i] >= max_rule_span) {
break;
}
if (data_array->AtIndex(pattern_end) == data_array_symbol) {
new_positions.insert(new_positions.end(), positions.begin() + i,
positions.begin() + i + num_subpatterns);
if (prefix_ends_with_x) {
new_positions.push_back(pattern_end);
}
}
++pattern_end;
}
}
return PhraseLocation(new_positions, phrase.Arity() + 1);
}
PhraseLocation FastIntersector::ExtendSuffixPhraseLocation(
PhraseLocation& suffix_location, const Phrase& phrase,
bool suffix_starts_with_x, int prev_symbol) const {
ExtendPhraseLocation(suffix_location);
vector<int> positions = *suffix_location.matchings;
int num_subpatterns = suffix_location.num_subpatterns;
vector<int> new_positions;
shared_ptr<DataArray> data_array = suffix_array->GetData();
int data_array_symbol = data_array->GetWordId(
vocabulary->GetTerminalValue(prev_symbol));
if (data_array_symbol == -1) {
return PhraseLocation(new_positions, num_subpatterns);
}
pair<int, int> range = GetSearchRange(suffix_starts_with_x);
for (size_t i = 0; i < positions.size(); i += num_subpatterns) {
int sent_id = data_array->GetSentenceId(positions[i]);
int sent_start = data_array->GetSentenceStart(sent_id);
int pattern_start = positions[i] - range.first;
int pattern_end = positions[i + num_subpatterns - 1] +
phrase.GetChunkLen(phrase.Arity()) - 1;
// Searches for the first symbol in the phrase before each suffix
// occurrence.
for (int j = range.first; j < range.second; ++j) {
if (pattern_start < sent_start ||
pattern_end - pattern_start >= max_rule_span) {
break;
}
if (data_array->AtIndex(pattern_start) == data_array_symbol) {
new_positions.push_back(pattern_start);
new_positions.insert(new_positions.end(),
positions.begin() + i + !suffix_starts_with_x,
positions.begin() + i + num_subpatterns);
}
--pattern_start;
}
}
return PhraseLocation(new_positions, phrase.Arity() + 1);
}
void FastIntersector::ExtendPhraseLocation(PhraseLocation& location) const {
if (location.matchings != NULL) {
return;
}
location.num_subpatterns = 1;
location.matchings = make_shared<vector<int>>();
for (int i = location.sa_low; i < location.sa_high; ++i) {
location.matchings->push_back(suffix_array->GetSuffix(i));
}
location.sa_low = location.sa_high = 0;
}
pair<int, int> FastIntersector::GetSearchRange(bool has_marginal_x) const {
if (has_marginal_x) {
return make_pair(min_gap_size + 1, max_rule_span);
} else {
return make_pair(1, 2);
}
}
} // namespace extractor
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