From 957d90991b4ec80b9877126c736bd60768b094aa Mon Sep 17 00:00:00 2001
From: Kenneth Heafield <github@kheafield.com>
Date: Mon, 17 Oct 2011 16:58:26 +0100
Subject: Chris, I'd like you to review this for use with your rules that
 contain <s> and </s>.

---
 decoder/ff_klm.cc | 72 +++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 49 insertions(+), 23 deletions(-)

diff --git a/decoder/ff_klm.cc b/decoder/ff_klm.cc
index 6d9aca54..658aef80 100644
--- a/decoder/ff_klm.cc
+++ b/decoder/ff_klm.cc
@@ -71,6 +71,8 @@ string KLanguageModel<Model>::usage(bool /*param*/,bool /*verbose*/) {
   return "KLanguageModel";
 }
 
+namespace {
+
 struct VMapper : public lm::ngram::EnumerateVocab {
   VMapper(vector<lm::WordIndex>* out) : out_(out), kLM_UNKNOWN_TOKEN(0) { out_->clear(); }
   void Add(lm::WordIndex index, const StringPiece &str) {
@@ -83,66 +85,90 @@ struct VMapper : public lm::ngram::EnumerateVocab {
   const lm::WordIndex kLM_UNKNOWN_TOKEN;
 };
 
-template <class Model>
-class KLanguageModelImpl {
+#pragma pack(push)
+#pragma pack(1)
 
-  static inline const lm::ngram::ChartState& RemnantLMState(const void* state) {
-    return *static_cast<const lm::ngram::ChartState*>(state);
+struct BoundaryAnnotatedState {
+  lm::ngram::ChartState state;
+  bool seen_bos, seen_eos;
+};
+
+#pragma pack(pop)
+
+void BoundaryCheck(bool &annotated, bool sub, double &ret) {
+  if (!sub) return;
+  if (annotated) {
+    ret -= 100.0;
+  } else {
+    annotated = true;
   }
+}
 
+} // namespace
+
+template <class Model>
+class KLanguageModelImpl {
  public:
   double LookupWords(const TRule& rule, const vector<const void*>& ant_states, double* oovs, void* remnant) {
     *oovs = 0;
     const vector<WordID>& e = rule.e();
-    lm::ngram::RuleScore<Model> ruleScore(*ngram_, *static_cast<lm::ngram::ChartState*>(remnant));
+    BoundaryAnnotatedState &annotated = *static_cast<BoundaryAnnotatedState*>(remnant);
+    lm::ngram::RuleScore<Model> ruleScore(*ngram_, annotated.state);
+    annotated.seen_bos = false;
+    annotated.seen_eos = false;
     unsigned i = 0;
+    double ret = 0.0;
     if (e.size()) {
       if (e[i] == kCDEC_SOS) {
         ++i;
         ruleScore.BeginSentence();
+        annotated.seen_bos = true;
       } else if (e[i] <= 0) {  // special case for left-edge NT
-        const lm::ngram::ChartState& prevState = RemnantLMState(ant_states[-e[0]]);
-        ruleScore.BeginNonTerminal(prevState, 0.0f);  // TODO
+        const BoundaryAnnotatedState &sub = *static_cast<const BoundaryAnnotatedState*>(ant_states[-e[0]]);
+        ruleScore.BeginNonTerminal(sub.state, 0.0f);
+        annotated.seen_bos = sub.seen_bos;
+        annotated.seen_eos = sub.seen_eos;
         ++i;
       }
     }
     for (; i < e.size(); ++i) {
       if (e[i] <= 0) {
-        const lm::ngram::ChartState& prevState = RemnantLMState(ant_states[-e[i]]);
-        ruleScore.NonTerminal(prevState, 0.0f);  // TODO
+        const BoundaryAnnotatedState &sub = *static_cast<const BoundaryAnnotatedState*>(ant_states[-e[i]]);
+        ruleScore.NonTerminal(sub.state, 0.0f);
+        BoundaryCheck(annotated.seen_bos, sub.seen_bos, ret);
+        BoundaryCheck(annotated.seen_eos, sub.seen_eos, ret);
       } else {
         const WordID cdec_word_or_class = ClassifyWordIfNecessary(e[i]);  // in future,
                                                                           // maybe handle emission
         const lm::WordIndex cur_word = MapWord(cdec_word_or_class); // map to LM's id
         if (cur_word == 0) (*oovs) += 1.0;
+        BoundaryCheck(annotated.seen_eos, cur_word == kEOS_, ret);
         ruleScore.Terminal(cur_word);
       }
     }
-    double ret = ruleScore.Finish();
-    static_cast<lm::ngram::ChartState*>(remnant)->ZeroRemaining();
+    ret += ruleScore.Finish();
+    annotated.state.ZeroRemaining();
     return ret;
   }
 
   // this assumes no target words on final unary -> goal rule.  is that ok?
   // for <s> (n-1 left words) and (n-1 right words) </s>
-  double FinalTraversalCost(const void* state, double* oovs) {
+  double FinalTraversalCost(const void* state_void, double* oovs) {
+    const BoundaryAnnotatedState &annotated = *static_cast<const BoundaryAnnotatedState*>(state_void);
     if (add_sos_eos_) {  // rules do not produce <s> </s>, so do it here
+      assert(!annotated.seen_bos);
+      assert(!annotated.seen_eos);
       lm::ngram::ChartState cstate;
       lm::ngram::RuleScore<Model> ruleScore(*ngram_, cstate);
       ruleScore.BeginSentence();
-      ruleScore.NonTerminal(RemnantLMState(state), 0.0f);
+      ruleScore.NonTerminal(annotated.state, 0.0f);
       ruleScore.Terminal(kEOS_);
       return ruleScore.Finish();
     } else {  // rules DO produce <s> ... </s>
-      double p = 0;
-      cerr << "not implemented"; abort(); // TODO
-      //if (!GetFlag(state, HAS_EOS_ON_RIGHT)) { p -= 100; }
-      //if (UnscoredSize(state) > 0) {  // are there unscored words
-      //  if (kSOS_ != IthUnscoredWord(0, state)) {
-      //    p -= 100 * UnscoredSize(state);
-      //  }
-      //}
-      return p;
+      double ret = 0.0;
+      if (!annotated.seen_bos) ret -= 100.0;
+      if (!annotated.seen_eos) ret -= 100.0;
+      return ret;
     }
   }
 
@@ -230,7 +256,7 @@ class KLanguageModelImpl {
     delete ngram_;
   }
 
-  int ReserveStateSize() const { return sizeof(lm::ngram::ChartState); }
+  int ReserveStateSize() const { return sizeof(BoundaryAnnotatedState); }
 
  private:
   const WordID kCDEC_UNK;
-- 
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