1 files changed, 62 insertions, 0 deletions
diff --git a/decoder/ff_wordalign.cc b/decoder/ff_wordalign.cc
index 338f1a72..ef3310b4 100644
--- a/decoder/ff_wordalign.cc
+++ b/decoder/ff_wordalign.cc
@@ -556,6 +556,68 @@ void BlunsomSynchronousParseHack::TraversalFeaturesImpl(const SentenceMetadata&
   SetStateMask(it->second, it->second + yield.size(), state);
 }
 
+IdentityCycleDetector::IdentityCycleDetector(const std::string& param) : FeatureFunction(2) {
+  length_min_ = 3;
+  if (!param.empty())
+    length_min_ = atoi(param.c_str());
+  assert(length_min_ >= 0);
+  ostringstream os;
+  os << "IdentityCycle_LenGT" << length_min_;
+  fid_ = FD::Convert(os.str());
+}
+
+inline bool IsIdentityTranslation(const void* state) {
+  return static_cast<const unsigned char*>(state)[0];
+}
+
+inline int SourceIndex(const void* state) {
+  unsigned char i = static_cast<const unsigned char*>(state)[1];
+  if (i == 255) return -1;
+  return i;
+}
+
+void IdentityCycleDetector::TraversalFeaturesImpl(const SentenceMetadata& smeta,
+                                     const Hypergraph::Edge& edge,
+                                     const std::vector<const void*>& ant_contexts,
+                                     SparseVector<double>* features,
+                                     SparseVector<double>* estimated_features,
+                                     void* context) const {
+  unsigned char* out_state = static_cast<unsigned char*>(context);
+  unsigned char& out_is_identity = out_state[0];
+  unsigned char& out_src_index = out_state[1];
+
+  if (edge.Arity() == 0) {
+    assert(edge.rule_->EWords() == 1);
+    assert(edge.rule_->FWords() == 1);
+    out_src_index = edge.i_;
+    out_is_identity = false;
+    if (edge.rule_->e_[0] == edge.rule_->f_[0]) {
+      const WordID word = edge.rule_->e_[0];
+      static map<WordID, bool> big_enough;
+      map<WordID,bool>::iterator it = big_enough_.find(word);
+      if (it == big_enough_.end()) {
+        out_is_identity = big_enough_[word] = strlen(TD::Convert(word)) >= length_min_;
+      } else {
+        out_is_identity = it->second;
+      }
+    }
+  } else if (edge.Arity() == 1) {
+    memcpy(context, ant_contexts[0], 2);
+  } else if (edge.Arity() == 2) {
+    bool left_identity = IsIdentityTranslation(ant_contexts[0]);
+    int left_index = SourceIndex(ant_contexts[0]);
+    bool right_identity = IsIdentityTranslation(ant_contexts[1]);
+    int right_index = SourceIndex(ant_contexts[1]);
+    if ((left_identity && left_index == right_index && !right_identity) ||
+        (right_identity && left_index == right_index && !left_identity)) {
+      features->set_value(fid_, 1.0);
+    }
+    out_is_identity = right_identity;
+    out_src_index = right_index;
+  } else { assert("really really bad"); }
+}
+
+
 InputIdentity::InputIdentity(const std::string& param) {}
 
 void InputIdentity::FireFeature(WordID src,