1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
|
#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
|
