Added character-level BLEU metric

7 files changed, 194 insertions, 19 deletions

diff --git a/mteval/comb_scorer.cc b/mteval/comb_scorer.cc
index 9fc37868..63f327ca 100644
--- a/mteval/comb_scorer.cc
+++ b/mteval/comb_scorer.cc
@@ -95,3 +95,96 @@ ScoreP BLEUTERCombinationScorer::ScoreFromString(const std::string& in) {
   r->ter = SentenceScorer::CreateScoreFromString(TER, in.substr(1 + bss));
   return ScoreP(r);
 }
+
+
+class BLEUCBLEUCombinationScore : public ScoreBase<BLEUCBLEUCombinationScore> {
+  friend class BLEUCBLEUCombinationScorer;
+ public:
+  ~BLEUCBLEUCombinationScore();
+  float ComputePartialScore() const { return 0.0;}
+  float ComputeScore() const {
+    return (bleu->ComputeScore() + cbleu->ComputeScore()) / 2.0f;
+  }
+  void ScoreDetails(string* details) const {
+    char buf[160];
+    sprintf(buf, "Combi = %.2f, BLEU = %.2f, CBLEU = %.2f",
+      ComputeScore()*100.0f, bleu->ComputeScore()*100.0f, cbleu->ComputeScore()*100.0f);
+    *details = buf;
+  }
+  void PlusPartialEquals(const Score& rhs, int oracle_e_cover, int oracle_f_cover, int src_len){}
+
+  void PlusEquals(const Score& delta, const float scale) {
+    bleu->PlusEquals(*static_cast<const BLEUCBLEUCombinationScore&>(delta).bleu, scale);
+    cbleu->PlusEquals(*static_cast<const BLEUCBLEUCombinationScore&>(delta).cbleu, scale);
+  }
+  void PlusEquals(const Score& delta) {
+    bleu->PlusEquals(*static_cast<const BLEUCBLEUCombinationScore&>(delta).bleu);
+    cbleu->PlusEquals(*static_cast<const BLEUCBLEUCombinationScore&>(delta).cbleu);
+  }
+
+
+
+  ScoreP GetOne() const {
+    BLEUCBLEUCombinationScore* res = new BLEUCBLEUCombinationScore;
+    res->bleu = bleu->GetOne();
+    res->cbleu = cbleu->GetOne();
+    return ScoreP(res);
+  }
+  ScoreP GetZero() const {
+    BLEUCBLEUCombinationScore* res = new BLEUCBLEUCombinationScore;
+    res->bleu = bleu->GetZero();
+    res->cbleu = cbleu->GetZero();
+    return ScoreP(res);
+  }
+  void Subtract(const Score& rhs, Score* res) const {
+    bleu->Subtract(*static_cast<const BLEUCBLEUCombinationScore&>(rhs).bleu,
+                   static_cast<BLEUCBLEUCombinationScore*>(res)->bleu.get());
+    cbleu->Subtract(*static_cast<const BLEUCBLEUCombinationScore&>(rhs).cbleu,
+                  static_cast<BLEUCBLEUCombinationScore*>(res)->cbleu.get());
+  }
+  void Encode(std::string* out) const {
+    string bs, ts;
+    bleu->Encode(&bs);
+    cbleu->Encode(&ts);
+    out->clear();
+    (*out) += static_cast<char>(bs.size());
+    (*out) += bs;
+    (*out) += ts;
+  }
+  bool IsAdditiveIdentity() const {
+    return bleu->IsAdditiveIdentity() && cbleu->IsAdditiveIdentity();
+  }
+ private:
+  ScoreP bleu;
+  ScoreP cbleu;
+};
+
+BLEUCBLEUCombinationScore::~BLEUCBLEUCombinationScore() {
+}
+
+BLEUCBLEUCombinationScorer::BLEUCBLEUCombinationScorer(const vector<vector<WordID> >& refs) {
+  bleu_ = SentenceScorer::CreateSentenceScorer(IBM_BLEU, refs);
+  cbleu_ = SentenceScorer::CreateSentenceScorer(CBLEU, refs);
+}
+
+BLEUCBLEUCombinationScorer::~BLEUCBLEUCombinationScorer() {
+}
+
+ScoreP BLEUCBLEUCombinationScorer::ScoreCCandidate(const vector<WordID>& hyp) const {
+  return ScoreP();
+}
+
+ScoreP BLEUCBLEUCombinationScorer::ScoreCandidate(const std::vector<WordID>& hyp) const {
+  BLEUCBLEUCombinationScore* res = new BLEUCBLEUCombinationScore;
+  res->bleu = bleu_->ScoreCandidate(hyp);
+  res->cbleu = cbleu_->ScoreCandidate(hyp);
+  return ScoreP(res);
+}
+
+ScoreP BLEUCBLEUCombinationScorer::ScoreFromString(const std::string& in) {
+  int bss = in[0];
+  BLEUCBLEUCombinationScore* r = new BLEUCBLEUCombinationScore;
+  r->bleu = SentenceScorer::CreateScoreFromString(IBM_BLEU, in.substr(1, bss));
+  r->cbleu = SentenceScorer::CreateScoreFromString(CBLEU, in.substr(1 + bss));
+  return ScoreP(r);
+}
diff --git a/mteval/comb_scorer.h b/mteval/comb_scorer.h
index d17d089d..1e2f0c25 100644
--- a/mteval/comb_scorer.h
+++ b/mteval/comb_scorer.h
@@ -14,4 +14,15 @@ class BLEUTERCombinationScorer : public SentenceScorer {
   ScorerP bleu_,ter_;
 };
 
+class BLEUCBLEUCombinationScorer : public SentenceScorer {
+ public:
+  BLEUCBLEUCombinationScorer(const std::vector<std::vector<WordID> >& refs);
+  ~BLEUCBLEUCombinationScorer();
+  ScoreP ScoreCandidate(const std::vector<WordID>& hyp) const;
+  ScoreP ScoreCCandidate(const std::vector<WordID>& hyp) const;
+  static ScoreP ScoreFromString(const std::string& in);
+ private:
+  ScorerP bleu_, cbleu_;
+};
+
 #endif
diff --git a/mteval/ns.cc b/mteval/ns.cc
index 2c8bd806..1d37c436 100644
--- a/mteval/ns.cc
+++ b/mteval/ns.cc
@@ -65,38 +65,41 @@ string EvaluationMetric::DetailedScore(const SufficientStats& stats) const {
 }
 
 enum BleuType { IBM, Koehn, NIST, QCRI };
-template <unsigned int N = 4u, BleuType BrevityType = IBM>
+template <unsigned int N = 4u, BleuType BrevityType = IBM, bool CharBased = false>
 struct BleuSegmentEvaluator : public SegmentEvaluator {
   BleuSegmentEvaluator(const vector<vector<WordID> >& refs, const EvaluationMetric* em) : evaluation_metric(em) {
-    assert(refs.size() > 0);
+    const vector<vector<WordID> >& local_refs = (CharBased ? Characterize(refs) : refs);
+
+    assert(local_refs.size() > 0);
     float tot = 0;
     int smallest = 9999999;
-    for (vector<vector<WordID> >::const_iterator ci = refs.begin();
-         ci != refs.end(); ++ci) {
+    for (vector<vector<WordID> >::const_iterator ci = local_refs.begin();
+         ci != local_refs.end(); ++ci) {
       lengths_.push_back(ci->size());
       tot += lengths_.back();
       if (lengths_.back() < smallest) smallest = lengths_.back();
       CountRef(*ci);
     }
     if (BrevityType == Koehn)
-      lengths_[0] = tot / refs.size();
+      lengths_[0] = tot / local_refs.size();
     if (BrevityType == NIST)
       lengths_[0] = smallest;
   }
 
   void Evaluate(const vector<WordID>& hyp, SufficientStats* out) const {
+    const vector<WordID>& local_hyp = (CharBased ? Characterize(hyp) : hyp);
     out->fields.resize(N + N + 2);
     out->id_ = evaluation_metric->MetricId();
     for (unsigned i = 0; i < N+N+2; ++i) out->fields[i] = 0;
 
-    ComputeNgramStats(hyp, &out->fields[0], &out->fields[N], true);
+    ComputeNgramStats(local_hyp, &out->fields[0], &out->fields[N], true);
     float& hyp_len = out->fields[2*N];
     float& ref_len = out->fields[2*N + 1];
-    hyp_len = hyp.size();
+    hyp_len = local_hyp.size();
     ref_len = lengths_[0];
     if (lengths_.size() > 1 && (BrevityType == IBM || BrevityType == QCRI)) {
       float bestd = 2000000;
-      float hl = hyp.size();
+      float hl = local_hyp.size();
       float bl = -1;
       for (vector<float>::const_iterator ci = lengths_.begin(); ci != lengths_.end(); ++ci) {
         if (fabs(*ci - hl) < bestd) {
@@ -187,12 +190,12 @@ struct BleuSegmentEvaluator : public SegmentEvaluator {
   mutable NGramCountMap ngrams_;
 };
 
-template <unsigned int N = 4u, BleuType BrevityType = IBM>
+template <unsigned int N = 4u, BleuType BrevityType = IBM, bool CharBased = false>
 struct BleuMetric : public EvaluationMetric {
   BleuMetric() : EvaluationMetric(BrevityType == IBM ? "IBM_BLEU" : (BrevityType == Koehn ? "KOEHN_BLEU" : (BrevityType == NIST ? "NIST_BLEU" : "QCRI_BLEU"))) {}
   unsigned SufficientStatisticsVectorSize() const { return N*2 + 2; }
   boost::shared_ptr<SegmentEvaluator> CreateSegmentEvaluator(const vector<vector<WordID> >& refs) const {
-    return boost::shared_ptr<SegmentEvaluator>(new BleuSegmentEvaluator<N,BrevityType>(refs, this));
+    return boost::shared_ptr<SegmentEvaluator>(new BleuSegmentEvaluator<N,BrevityType, CharBased>(refs, this));
   }
   float ComputeBreakdown(const SufficientStats& stats, float* bp, vector<float>* out) const {
     if (out) { out->clear(); }
@@ -290,6 +293,8 @@ EvaluationMetric* EvaluationMetric::Instance(const string& imetric_id) {
       m = new CERMetric;
     } else if (metric_id == "WER") {
       m = new WERMetric;
+    } else if (metric_id == "CBLEU") {
+      return new BleuMetric<5, IBM, true>;
     } else {
       cerr << "Implement please: " << metric_id << endl;
       abort();
@@ -322,4 +327,3 @@ void SufficientStats::Encode(string* out) const {
     os << ' ' << fields[i];
   *out = os.str();
 }
-
diff --git a/mteval/ns.h b/mteval/ns.h
index f6329b65..16edfdf0 100644
--- a/mteval/ns.h
+++ b/mteval/ns.h
@@ -8,6 +8,9 @@
 #include "wordid.h"
 #include <iostream>
 
+std::vector<WordID> Characterize(const std::vector<WordID>& reference);
+std::vector<std::vector<WordID> > Characterize(const std::vector<std::vector<WordID> >& references);
+
 class SufficientStats {
  public:
   SufficientStats() : id_() {}
diff --git a/mteval/scorer.cc b/mteval/scorer.cc
index 4c05dbd8..71e05e9c 100644
--- a/mteval/scorer.cc
+++ b/mteval/scorer.cc
@@ -49,12 +49,17 @@ ScoreType ScoreTypeFromString(const string& st) {
     return METEOR;
   if (sl == "wer")
     return WER;
+  if (sl == "cbleu")
+    return CBLEU;
+  if (sl == "bleu_cbleu")
+    return BLEU_plus_CBLEU_over_2;
   cerr << "Don't understand score type '" << st << "', defaulting to ibm_bleu.\n";
+  assert (false);
   return IBM_BLEU;
 }
 
 static char const* score_names[]={
-  "IBM_BLEU", "NIST_BLEU", "Koehn_BLEU", "TER", "BLEU_minus_TER_over_2", "SER", "AER", "IBM_BLEU_3", "METEOR", "WER"
+  "IBM_BLEU", "NIST_BLEU", "Koehn_BLEU", "TER", "BLEU_minus_TER_over_2", "SER", "AER", "IBM_BLEU_3", "METEOR", "WER", "CBLEU", "BLEU_plus_CBLEU_over_2"
 };
 
 std::string StringFromScoreType(ScoreType st) {
@@ -291,6 +296,21 @@ ScoreP BLEUScorerBase::ScoreFromString(const string& in) {
   return ScoreP(r);
 }
 
+class CBLEUScorer : public BLEUScorerBase {
+ public:
+  CBLEUScorer(const vector<vector<WordID> >& references,
+  int n=5) : BLEUScorerBase(Characterize(references), n), lengths_(references.size()) {
+    for (unsigned i=0; i < references.size(); ++i)
+      lengths_[i] = Characterize(references[i]).size();
+  }
+
+  float ComputeRefLength(const vector<WordID>& hyp) const {
+    return 1000;
+  }
+ private:
+  vector<int> lengths_;
+};
+
 class IBM_BLEUScorer : public BLEUScorerBase {
  public:
     IBM_BLEUScorer(const vector<vector<WordID> >& references,
@@ -362,8 +382,10 @@ ScorerP SentenceScorer::CreateSentenceScorer(const ScoreType type,
     case TER: r = new TERScorer(refs);break;
     case SER: r = new SERScorer(refs);break;
     case BLEU_minus_TER_over_2: r = new BLEUTERCombinationScorer(refs);break;
+    case BLEU_plus_CBLEU_over_2: r = new BLEUCBLEUCombinationScorer(refs); break;
     case METEOR: r = new ExternalSentenceScorer(ScoreServerManager::Instance("meteor"), refs); break;
     case WER: r = new WERScorer(refs);break;
+    case CBLEU: r = new CBLEUScorer(refs, 5); break;
     default:
       assert(!"Not implemented!");
   }
@@ -410,6 +432,10 @@ ScoreP SentenceScorer::CreateScoreFromString(const ScoreType type, const string&
       return ExternalSentenceScorer::ScoreFromString(ScoreServerManager::Instance("meteor"), in);
     case WER:
       return WERScorer::ScoreFromString(in);
+    case CBLEU:
+      return CBLEUScorer::ScoreFromString(in);
+    case BLEU_plus_CBLEU_over_2:
+      return BLEUCBLEUCombinationScorer::ScoreFromString(in);
     default:
       assert(!"Not implemented!");
   }
@@ -685,3 +711,33 @@ void DocStreamScorer::update(const std::string& ref) {
 	TD::ConvertSentence(ref, &refs[0]);
 	scorer = ScorerP(SentenceScorer::CreateSentenceScorer(type, refs, src_line));
 }
+
+vector<WordID> Characterize(const vector<WordID>& reference) {
+  vector<WordID> r;
+  string space = " ";
+  for (WordID word_id: reference) {
+    string word = TD::Convert(word_id);
+    unsigned i = 0;
+    while (i < word.length()) {
+      unsigned char_length = UTF8Len(word[i]);
+      string c = word.substr(i, char_length);
+      i += char_length;
+      r.push_back(TD::Convert(c));
+    }
+    r.push_back(TD::Convert(space));
+  }
+
+  // Remove the last space
+  if (r.size() > 0) {
+    r.pop_back();
+  }
+  return r;
+}
+
+vector<vector<WordID>> Characterize(const vector<vector<WordID> >& references) {
+  vector<vector<WordID> > r;
+  for (const vector<WordID>& reference : references) {
+    r.push_back(Characterize(reference));
+  }
+  return r;
+}
diff --git a/mteval/scorer.h b/mteval/scorer.h
index a411f14b..e7de0118 100644
--- a/mteval/scorer.h
+++ b/mteval/scorer.h
@@ -17,10 +17,14 @@ class ErrorSurface;
 class Hypergraph;  // needed for alignment
 
 //TODO: BLEU N (N separate arg, not part of enum)?
-enum ScoreType { IBM_BLEU, NIST_BLEU, Koehn_BLEU, TER, BLEU_minus_TER_over_2, SER, AER, IBM_BLEU_3, METEOR, WER };
+enum ScoreType { IBM_BLEU, NIST_BLEU, Koehn_BLEU, TER, BLEU_minus_TER_over_2, SER, AER, IBM_BLEU_3, METEOR, WER, CBLEU, BLEU_plus_CBLEU_over_2 };
 ScoreType ScoreTypeFromString(const std::string& st);
 std::string StringFromScoreType(ScoreType st);
 
+std::vector<WordID> Characterize(const std::vector<WordID>& reference);
+std::vector<std::vector<WordID> > Characterize(const std::vector<std::vector<WordID> >& references);
+
+
 class Score : public boost::intrusive_refcount<Score> {
  public:
   virtual ~Score();
diff --git a/mteval/wer.cc b/mteval/wer.cc
index c806b3be..b8cfd3d8 100644
--- a/mteval/wer.cc
+++ b/mteval/wer.cc
@@ -31,16 +31,17 @@ class WERScore : public ScoreBase<WERScore> {
  WERScore() : stats(0,kDUMMY_LAST_ENTRY) {}
   float ComputePartialScore() const { return 0.0;}
   float ComputeScore() const {
+    if (static_cast<float>(stats[kCHARCOUNT]) < 0.5)
+      return 0;
     return static_cast<float>(stats[kEDITDISTANCE]) / static_cast<float>(stats[kCHARCOUNT]);
   }
   void ScoreDetails(string* details) const;
   void PlusPartialEquals(const Score& rhs, int oracle_e_cover, int oracle_f_cover, int src_len){}
   void PlusEquals(const Score& delta, const float scale) {
-    if (scale==1)
-      stats += static_cast<const WERScore&>(delta).stats;
-    if (scale==-1)
-      stats -= static_cast<const WERScore&>(delta).stats;
-    throw std::runtime_error("WERScore::PlusEquals with scale != +-1");
+    const WERScore& delta_stats = static_cast<const WERScore&>(delta);
+    for (unsigned i = 0; i < kDUMMY_LAST_ENTRY; ++i) {
+        stats[i] += scale * static_cast<float>(delta_stats.stats[i]);
+    }
  }
   void PlusEquals(const Score& delta) {
     stats += static_cast<const WERScore&>(delta).stats;
@@ -88,7 +89,7 @@ void WERScore::ScoreDetails(std::string* details) const {
 }
 
 WERScorer::~WERScorer() {}
-WERScorer::WERScorer(const vector<vector<WordID> >& refs) {}
+WERScorer::WERScorer(const vector<vector<WordID> >& refs) {this->refs = refs;}
 
 ScoreP WERScorer::ScoreCCandidate(const vector<WordID>& hyp) const {
   return ScoreP();
@@ -97,6 +98,9 @@ ScoreP WERScorer::ScoreCCandidate(const vector<WordID>& hyp) const {
 float WERScorer::Calculate(const std::vector<WordID>& hyp, const Sentence& ref, int& edits, int& char_count) const {
   edits = cdec::LevenshteinDistance(hyp, ref);
   char_count = ref.size();
+  if (char_count == 0) {
+    return 0;
+  }
   return static_cast<float>(edits) / static_cast<float>(char_count);
 }