1 files changed, 206 insertions, 0 deletions
diff --git a/decoder/phrasebased_translator.cc b/decoder/phrasebased_translator.cc
new file mode 100644
index 00000000..5eb70876
--- /dev/null
+++ b/decoder/phrasebased_translator.cc
@@ -0,0 +1,206 @@
+#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>()),
+      kSOURCE_RULE(new TRule("[X] ||| [X,1] ||| [X,1]", true)),
+      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_;
+          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;
+  TRulePtr kSOURCE_RULE;
+  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::Translate(const std::string& input,
+                                      SentenceMetadata* smeta,
+                                      const std::vector<double>& weights,
+                                      Hypergraph* minus_lm_forest) {
+  return pimpl_->Translate(input, smeta, weights, minus_lm_forest);
+}