major restructure of the training code

1 files changed, 254 insertions, 0 deletions

diff --git a/training/dtrain/score.cc b/training/dtrain/score.cc
new file mode 100644
index 00000000..34fc86a9
--- /dev/null
+++ b/training/dtrain/score.cc
@@ -0,0 +1,254 @@
+#include "score.h"
+
+namespace dtrain
+{
+
+
+/*
+ * bleu
+ *
+ * as in "BLEU: a Method for Automatic Evaluation
+ *        of Machine Translation"
+ * (Papineni et al. '02)
+ *
+ * NOTE: 0 if for one n \in {1..N} count is 0
+ */
+score_t
+BleuScorer::Bleu(NgramCounts& counts, const unsigned hyp_len, const unsigned ref_len)
+{
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  unsigned M = N_;
+  vector<score_t> v = w_;
+  if (ref_len < N_) {
+    M = ref_len;
+    for (unsigned i = 0; i < M; i++) v[i] = 1/((score_t)M);
+  }
+  score_t sum = 0;
+  for (unsigned i = 0; i < M; i++) {
+    if (counts.sum_[i] == 0 || counts.clipped_[i] == 0) return 0.;
+    sum += v[i] * log((score_t)counts.clipped_[i]/counts.sum_[i]);
+  }
+  return brevity_penalty(hyp_len, ref_len) * exp(sum);
+}
+
+score_t
+BleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                  const unsigned /*rank*/, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  NgramCounts counts = make_ngram_counts(hyp, ref, N_);
+  return Bleu(counts, hyp_len, ref_len);
+}
+
+/*
+ * 'stupid' bleu
+ *
+ * as in "ORANGE: a Method for Evaluating
+ *        Automatic Evaluation Metrics
+ *        for Machine Translation"
+ * (Lin & Och '04)
+ *
+ * NOTE: 0 iff no 1gram match
+ */
+score_t
+StupidBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned /*rank*/, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  NgramCounts counts = make_ngram_counts(hyp, ref, N_);
+  unsigned M = N_;
+  vector<score_t> v = w_;
+  if (ref_len < N_) {
+    M = ref_len;
+    for (unsigned i = 0; i < M; i++) v[i] = 1/((score_t)M);
+  }
+  score_t sum = 0, add = 0;
+  for (unsigned i = 0; i < M; i++) {
+    if (i == 0 && (counts.sum_[i] == 0 || counts.clipped_[i] == 0)) return 0.;
+    if (i == 1) add = 1;
+    sum += v[i] * log(((score_t)counts.clipped_[i] + add)/((counts.sum_[i] + add)));
+  }
+  return  brevity_penalty(hyp_len, ref_len) * exp(sum);
+}
+
+/*
+ * smooth bleu
+ *
+ * as in "An End-to-End Discriminative Approach
+ *        to Machine Translation"
+ * (Liang et al. '06)
+ *
+ * NOTE: max is 0.9375 (with N=4)
+ */
+score_t
+SmoothBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned /*rank*/, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  NgramCounts counts = make_ngram_counts(hyp, ref, N_);
+  unsigned M = N_;
+  if (ref_len < N_) M = ref_len;
+  score_t sum = 0.;
+  vector<score_t> i_bleu;
+  for (unsigned i = 0; i < M; i++) i_bleu.push_back(0.);
+  for (unsigned i = 0; i < M; i++) {
+    if (counts.sum_[i] == 0 || counts.clipped_[i] == 0) {
+      break;
+    } else {
+      score_t i_ng = log((score_t)counts.clipped_[i]/counts.sum_[i]);
+      for (unsigned j = i; j < M; j++) {
+        i_bleu[j] += (1/((score_t)j+1)) * i_ng;
+      }
+    }
+    sum += exp(i_bleu[i])/pow(2.0, (double)(N_-i));
+  }
+  return brevity_penalty(hyp_len, ref_len) * sum;
+}
+
+/*
+ * 'sum' bleu
+ *
+ * sum up Ngram precisions
+ */
+score_t
+SumBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned /*rank*/, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  NgramCounts counts = make_ngram_counts(hyp, ref, N_);
+  unsigned M = N_;
+  if (ref_len < N_) M = ref_len;
+  score_t sum = 0.;
+  unsigned j = 1;
+  for (unsigned i = 0; i < M; i++) {
+    if (counts.sum_[i] == 0 || counts.clipped_[i] == 0) break;
+    sum += ((score_t)counts.clipped_[i]/counts.sum_[i])/pow(2.0, (double) (N_-j+1));
+    j++;
+  }
+  return brevity_penalty(hyp_len, ref_len) * sum;
+}
+
+/*
+ * 'sum' (exp) bleu
+ *
+ * sum up exp(Ngram precisions)
+ */
+score_t
+SumExpBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned /*rank*/, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  NgramCounts counts = make_ngram_counts(hyp, ref, N_);
+  unsigned M = N_;
+  if (ref_len < N_) M = ref_len;
+  score_t sum = 0.;
+  unsigned j = 1;
+  for (unsigned i = 0; i < M; i++) {
+    if (counts.sum_[i] == 0 || counts.clipped_[i] == 0) break;
+    sum += exp(((score_t)counts.clipped_[i]/counts.sum_[i]))/pow(2.0, (double) (N_-j+1));
+    j++;
+  }
+  return brevity_penalty(hyp_len, ref_len) * sum;
+}
+
+/*
+ * 'sum' (whatever) bleu
+ *
+ * sum up exp(weight * log(Ngram precisions))
+ */
+score_t
+SumWhateverBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned /*rank*/, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (hyp_len == 0 || ref_len == 0) return 0.;
+  NgramCounts counts = make_ngram_counts(hyp, ref, N_);
+  unsigned M = N_;
+  vector<score_t> v = w_;
+  if (ref_len < N_) {
+    M = ref_len;
+    for (unsigned i = 0; i < M; i++) v[i] = 1/((score_t)M);
+  }
+  score_t sum = 0.;
+  unsigned j = 1;
+  for (unsigned i = 0; i < M; i++) {
+    if (counts.sum_[i] == 0 || counts.clipped_[i] == 0) break;
+    sum += exp(v[i] * log(((score_t)counts.clipped_[i]/counts.sum_[i])))/pow(2.0, (double) (N_-j+1));
+    j++;
+  }
+  return brevity_penalty(hyp_len, ref_len) * sum;
+}
+
+/*
+ * approx. bleu
+ *
+ * as in "Online Large-Margin Training of Syntactic
+ *        and Structural Translation Features"
+ * (Chiang et al. '08)
+ *
+ * NOTE: Needs some more code in dtrain.cc .
+ *       No scaling by src len.
+ */
+score_t
+ApproxBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned rank, const unsigned src_len)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (ref_len == 0) return 0.;
+  score_t score = 0.;
+  NgramCounts counts(N_);
+  if (hyp_len > 0) {
+    counts = make_ngram_counts(hyp, ref, N_);
+    NgramCounts tmp = glob_onebest_counts_ + counts;
+    score = Bleu(tmp, hyp_len, ref_len);
+  }
+  if (rank == 0) { // 'context of 1best translations'
+    glob_onebest_counts_ += counts;
+    glob_onebest_counts_ *= discount_;
+    glob_hyp_len_ = discount_ * (glob_hyp_len_ + hyp_len);
+    glob_ref_len_ = discount_ * (glob_ref_len_ + ref_len);
+    glob_src_len_ = discount_ * (glob_src_len_ + src_len);
+  }
+  return score;
+}
+
+/*
+ * Linear (Corpus) Bleu
+ *
+ * as in "Lattice Minimum Bayes-Risk Decoding
+ *        for Statistical Machine Translation"
+ * (Tromble et al. '08)
+ *
+ */
+score_t
+LinearBleuScorer::Score(vector<WordID>& hyp, vector<WordID>& ref,
+                        const unsigned rank, const unsigned /*src_len*/)
+{
+  unsigned hyp_len = hyp.size(), ref_len = ref.size();
+  if (ref_len == 0) return 0.;
+  unsigned M = N_;
+  if (ref_len < N_) M = ref_len;
+  NgramCounts counts(M);
+  if (hyp_len > 0)
+    counts = make_ngram_counts(hyp, ref, M);
+  score_t ret = 0.;
+  for (unsigned i = 0; i < M; i++) {
+    if (counts.sum_[i] == 0 || onebest_counts_.sum_[i] == 0) break;
+    ret += counts.sum_[i]/onebest_counts_.sum_[i];
+  }
+  ret = -(hyp_len/(score_t)onebest_len_) + (1./M) * ret;
+  if (rank == 0) {
+    onebest_len_ += hyp_len;
+    onebest_counts_ += counts;
+  }
+  return ret;
+}
+
+
+} // namespace
+