2 files changed, 133 insertions, 0 deletions
diff --git a/mteval/wer.cc b/mteval/wer.cc
new file mode 100644
index 00000000..c806b3be
--- /dev/null
+++ b/mteval/wer.cc
@@ -0,0 +1,117 @@
+#include "wer.h"
+
+#include <cstdio>
+#include <cassert>
+#include <iostream>
+#include <limits>
+#include <sstream>
+#ifndef HAVE_OLD_CPP
+# include <unordered_map>
+#else
+# include <tr1/unordered_map>
+namespace std { using std::tr1::unordered_map; }
+#endif
+#include <set>
+#include <valarray>
+#include <boost/functional/hash.hpp>
+#include <stdexcept>
+#include "tdict.h"
+#include "levenshtein.h"
+
+using namespace std;
+
+class WERScore : public ScoreBase<WERScore> {
+  friend class WERScorer;
+
+ public:
+  static const unsigned kEDITDISTANCE = 0;
+  static const unsigned kCHARCOUNT = 1;
+  static const unsigned kDUMMY_LAST_ENTRY = 2;
+
+ WERScore() : stats(0,kDUMMY_LAST_ENTRY) {}
+  float ComputePartialScore() const { return 0.0;}
+  float ComputeScore() const {
+    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");
+ }
+  void PlusEquals(const Score& delta) {
+    stats += static_cast<const WERScore&>(delta).stats;
+  }
+
+  ScoreP GetZero() const {
+    return ScoreP(new WERScore);
+  }
+  ScoreP GetOne() const {
+    return ScoreP(new WERScore);
+  }
+  void Subtract(const Score& rhs, Score* res) const {
+    static_cast<WERScore*>(res)->stats = stats - static_cast<const WERScore&>(rhs).stats;
+  }
+  void Encode(std::string* out) const {
+    ostringstream os;
+    os << stats[kEDITDISTANCE] << ' '
+       << stats[kCHARCOUNT];
+    *out = os.str();
+  }
+  bool IsAdditiveIdentity() const {
+    for (int i = 0; i < kDUMMY_LAST_ENTRY; ++i)
+      if (stats[i] != 0) return false;
+    return true;
+  }
+ private:
+  valarray<int> stats;
+};
+
+ScoreP WERScorer::ScoreFromString(const std::string& data) {
+  istringstream is(data);
+  WERScore* r = new WERScore;
+  is >> r->stats[WERScore::kEDITDISTANCE]
+     >> r->stats[WERScore::kCHARCOUNT];
+  return ScoreP(r);
+}
+
+void WERScore::ScoreDetails(std::string* details) const {
+  char buf[200];
+  sprintf(buf, "WER = %.2f, edits=%d, len=%d",
+     ComputeScore() * 100.0f,
+     stats[kEDITDISTANCE],
+     stats[kCHARCOUNT]);
+  *details = buf;
+}
+
+WERScorer::~WERScorer() {}
+WERScorer::WERScorer(const vector<vector<WordID> >& refs) {}
+
+ScoreP WERScorer::ScoreCCandidate(const vector<WordID>& hyp) const {
+  return ScoreP();
+}
+
+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();
+  return static_cast<float>(edits) / static_cast<float>(char_count);
+}
+
+ScoreP WERScorer::ScoreCandidate(const std::vector<WordID>& hyp) const {
+  float best_score = numeric_limits<float>::max();
+  WERScore* res = new WERScore;
+  for (int i = 0; i < refs.size(); ++i) {
+    int edits, char_count;
+    const vector<WordID>& ref = refs[i];
+    float score = Calculate(hyp, ref, edits, char_count);
+    if (score < best_score) {
+      res->stats[WERScore::kEDITDISTANCE] = edits;
+      res->stats[WERScore::kCHARCOUNT] = char_count;
+      best_score = score;
+    }
+  }
+  return ScoreP(res);
+}
diff --git a/mteval/wer.h b/mteval/wer.h
new file mode 100644
index 00000000..3a799f58
--- /dev/null
+++ b/mteval/wer.h
@@ -0,0 +1,16 @@
+#ifndef WER_H_
+#define WER_H_
+
+#include "scorer.h"
+
+class WERScorer : public SentenceScorer {
+ public:
+  WERScorer(const std::vector<std::vector<WordID> >& references);
+  ~WERScorer();
+  ScoreP ScoreCandidate(const std::vector<WordID>& hyp) const;
+  ScoreP ScoreCCandidate(const std::vector<WordID>& hyp) const;
+  static ScoreP ScoreFromString(const std::string& data);
+  float Calculate(const std::vector<WordID>& hyp, const Sentence& ref, int& edits, int& char_count) const;
+};
+
+#endif