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
196
197
198
199
200
201
202
203
204
205
206
|
#include "phrasebased_translator.h"
#include <queue>
#include <iostream>
#include <tr1/unordered_map>
#include <tr1/unordered_set>
#include <boost/tuple/tuple.hpp>
#include <boost/functional/hash.hpp>
#include "sentence_metadata.h"
#include "tdict.h"
#include "hg.h"
#include "filelib.h"
#include "lattice.h"
#include "phrasetable_fst.h"
#include "array2d.h"
using namespace std;
using namespace std::tr1;
using namespace boost::tuples;
struct Coverage : public vector<bool> {
explicit Coverage(int n, bool v = false) : vector<bool>(n, v), first_gap() {}
void Cover(int i, int j) {
vector<bool>::iterator it = this->begin() + i;
vector<bool>::iterator end = this->begin() + j;
while (it != end)
*it++ = true;
if (first_gap == i) {
first_gap = j;
it = end;
while (*it && it != this->end()) {
++it;
++first_gap;
}
}
}
bool Collides(int i, int j) const {
vector<bool>::const_iterator it = this->begin() + i;
vector<bool>::const_iterator end = this->begin() + j;
while (it != end)
if (*it++) return true;
return false;
}
int GetFirstGap() const { return first_gap; }
private:
int first_gap;
};
struct CoverageHash {
size_t operator()(const Coverage& cov) const {
return hasher_(static_cast<const vector<bool>&>(cov));
}
private:
boost::hash<vector<bool> > hasher_;
};
ostream& operator<<(ostream& os, const Coverage& cov) {
os << '[';
for (int i = 0; i < cov.size(); ++i)
os << (cov[i] ? '*' : '.');
return os << " gap=" << cov.GetFirstGap() << ']';
}
typedef unordered_map<Coverage, int, CoverageHash> CoverageNodeMap;
typedef unordered_set<Coverage, CoverageHash> UniqueCoverageSet;
struct PhraseBasedTranslatorImpl {
PhraseBasedTranslatorImpl(const boost::program_options::variables_map& conf) :
add_pass_through_rules(conf.count("add_pass_through_rules")),
max_distortion(conf["pb_max_distortion"].as<int>()),
kCONCAT_RULE(new TRule("[X] ||| [X,1] [X,2] ||| [X,1] [X,2]", true)),
kNT_TYPE(TD::Convert("X") * -1) {
assert(max_distortion >= 0);
vector<string> gfiles = conf["grammar"].as<vector<string> >();
assert(gfiles.size() == 1);
cerr << "Reading phrasetable from " << gfiles.front() << endl;
ReadFile in(gfiles.front());
fst.reset(LoadTextPhrasetable(in.stream()));
}
struct State {
State(const Coverage& c, int _i, int _j, const FSTNode* q) :
coverage(c), i(_i), j(_j), fst(q) {}
Coverage coverage;
int i;
int j;
const FSTNode* fst;
};
// we keep track of unique coverages that have been extended since it's
// possible to "extend" the same coverage twice, e.g. translate "a b c"
// with phrases "a" "b" "a b" and "c". There are two ways to cover "a b"
void EnqueuePossibleContinuations(const Coverage& coverage, queue<State>* q, UniqueCoverageSet* ucs) {
if (ucs->insert(coverage).second) {
const int gap = coverage.GetFirstGap();
const int end = min(static_cast<int>(coverage.size()), gap + max_distortion + 1);
for (int i = gap; i < end; ++i)
if (!coverage[i]) q->push(State(coverage, i, i, fst.get()));
}
}
bool Translate(const std::string& input,
SentenceMetadata* smeta,
const std::vector<double>& weights,
Hypergraph* minus_lm_forest) {
Lattice lattice;
LatticeTools::ConvertTextOrPLF(input, &lattice);
smeta->SetSourceLength(lattice.size());
size_t est_nodes = lattice.size() * lattice.size() * (1 << max_distortion);
minus_lm_forest->ReserveNodes(est_nodes, est_nodes * 100);
if (add_pass_through_rules) {
SparseVector<double> feats;
feats.set_value(FD::Convert("PassThrough"), 1);
for (int i = 0; i < lattice.size(); ++i) {
const vector<LatticeArc>& arcs = lattice[i];
for (int j = 0; j < arcs.size(); ++j) {
fst->AddPassThroughTranslation(arcs[j].label, feats);
// TODO handle lattice edge features
}
}
}
CoverageNodeMap c;
queue<State> q;
UniqueCoverageSet ucs;
const Coverage empty_cov(lattice.size(), false);
const Coverage goal_cov(lattice.size(), true);
EnqueuePossibleContinuations(empty_cov, &q, &ucs);
c[empty_cov] = 0; // have to handle the left edge specially
while(!q.empty()) {
const State s = q.front();
q.pop();
// cerr << "(" << s.i << "," << s.j << " ptr=" << s.fst << ") cov=" << s.coverage << endl;
const vector<LatticeArc>& arcs = lattice[s.j];
if (s.fst->HasData()) {
Coverage new_cov = s.coverage;
new_cov.Cover(s.i, s.j);
EnqueuePossibleContinuations(new_cov, &q, &ucs);
const vector<TRulePtr>& phrases = s.fst->GetTranslations()->GetRules();
const int phrase_head_index = minus_lm_forest->AddNode(kNT_TYPE)->id_;
for (int i = 0; i < phrases.size(); ++i) {
Hypergraph::Edge* edge = minus_lm_forest->AddEdge(phrases[i], Hypergraph::TailNodeVector());
edge->feature_values_ = edge->rule_->scores_;
edge->i_ = s.i;
edge->j_ = s.j;
minus_lm_forest->ConnectEdgeToHeadNode(edge->id_, phrase_head_index);
}
CoverageNodeMap::iterator cit = c.find(s.coverage);
assert(cit != c.end());
const int tail_node_plus1 = cit->second;
if (tail_node_plus1 == 0) { // left edge
c[new_cov] = phrase_head_index + 1;
} else { // not left edge
int& head_node_plus1 = c[new_cov];
if (!head_node_plus1)
head_node_plus1 = minus_lm_forest->AddNode(kNT_TYPE)->id_ + 1;
Hypergraph::TailNodeVector tail(2, tail_node_plus1 - 1);
tail[1] = phrase_head_index;
const int concat_edge = minus_lm_forest->AddEdge(kCONCAT_RULE, tail)->id_;
minus_lm_forest->ConnectEdgeToHeadNode(concat_edge, head_node_plus1 - 1);
}
}
if (s.j == lattice.size()) continue;
for (int l = 0; l < arcs.size(); ++l) {
const LatticeArc& arc = arcs[l];
const FSTNode* next_fst_state = s.fst->Extend(arc.label);
const int next_j = s.j + arc.dist2next;
if (next_fst_state &&
!s.coverage.Collides(s.i, next_j)) {
q.push(State(s.coverage, s.i, next_j, next_fst_state));
}
}
}
if (add_pass_through_rules)
fst->ClearPassThroughTranslations();
int pregoal_plus1 = c[goal_cov];
if (pregoal_plus1 > 0) {
TRulePtr kGOAL_RULE(new TRule("[Goal] ||| [X,1] ||| [X,1]"));
int goal = minus_lm_forest->AddNode(TD::Convert("Goal") * -1)->id_;
int gedge = minus_lm_forest->AddEdge(kGOAL_RULE, Hypergraph::TailNodeVector(1, pregoal_plus1 - 1))->id_;
minus_lm_forest->ConnectEdgeToHeadNode(gedge, goal);
// they are almost topo, but not quite always
minus_lm_forest->TopologicallySortNodesAndEdges(goal);
minus_lm_forest->Reweight(weights);
return true;
} else {
return false; // composition failed
}
}
const bool add_pass_through_rules;
const int max_distortion;
const TRulePtr kCONCAT_RULE;
const WordID kNT_TYPE;
boost::shared_ptr<FSTNode> fst;
};
PhraseBasedTranslator::PhraseBasedTranslator(const boost::program_options::variables_map& conf) :
pimpl_(new PhraseBasedTranslatorImpl(conf)) {}
bool PhraseBasedTranslator::TranslateImpl(const std::string& input,
SentenceMetadata* smeta,
const std::vector<double>& weights,
Hypergraph* minus_lm_forest) {
return pimpl_->Translate(input, smeta, weights, minus_lm_forest);
}
|
