1 files changed, 65 insertions, 0 deletions
diff --git a/training/dtrain/update.h b/training/dtrain/update.h
new file mode 100644
index 00000000..57671ce1
--- /dev/null
+++ b/training/dtrain/update.h
@@ -0,0 +1,65 @@
+#ifndef _DTRAIN_UPDATE_H_
+#define _DTRAIN_UPDATE_H_
+
+namespace dtrain
+{
+
+bool
+CmpHypsByGold(ScoredHyp a, ScoredHyp b)
+{
+  return a.gold > b.gold;
+}
+
+/*
+ * multipartite ranking
+ *  sort (descending) by bleu
+ *  compare top X (hi) to middle Y (med) and low X (lo)
+ *  cmp middle Y to low X
+ */
+inline size_t
+CollectUpdates(vector<ScoredHyp>* s,
+               SparseVector<weight_t>& updates,
+               float margin=1.0)
+{
+  size_t num_pairs = 0;
+  size_t sz = s->size();
+  if (sz < 2) return 0;
+  sort(s->begin(), s->end(), CmpHypsByGold);
+  size_t sep = round(sz*0.1);
+  size_t sep_hi = sep;
+  if (sz > 4) {
+    while
+      (sep_hi < sz && (*s)[sep_hi-1].gold == (*s)[sep_hi].gold) ++sep_hi;
+  }
+  else sep_hi = 1;
+  for (size_t i = 0; i < sep_hi; i++) {
+    for (size_t j = sep_hi; j < sz; j++) {
+      if (((*s)[i].model-(*s)[j].model) > margin)
+        continue;
+      if ((*s)[i].gold != (*s)[j].gold) {
+        updates += (*s)[i].f-(*s)[j].f;
+        num_pairs++;
+      }
+    }
+  }
+  size_t sep_lo = sz-sep;
+  while (sep_lo > 0 && (*s)[sep_lo-1].gold == (*s)[sep_lo].gold)
+    --sep_lo;
+  for (size_t i = sep_hi; i < sep_lo; i++) {
+    for (size_t j = sep_lo; j < sz; j++) {
+      if (((*s)[i].model-(*s)[j].model) > margin)
+        continue;
+      if ((*s)[i].gold != (*s)[j].gold) {
+        updates += (*s)[i].f-(*s)[j].f;
+        num_pairs++;
+      }
+    }
+  }
+
+  return num_pairs;
+}
+
+} // namespace
+
+#endif
+