1 files changed, 88 insertions, 0 deletions
diff --git a/rst_parser/arc_factored.h b/rst_parser/arc_factored.h
new file mode 100644
index 00000000..e99be482
--- /dev/null
+++ b/rst_parser/arc_factored.h
@@ -0,0 +1,88 @@
+#ifndef _ARC_FACTORED_H_
+#define _ARC_FACTORED_H_
+
+#include <iostream>
+#include <cassert>
+#include <vector>
+#include <utility>
+#include "array2d.h"
+#include "sparse_vector.h"
+#include "prob.h"
+#include "weights.h"
+
+struct SpanningTree {
+  SpanningTree() : roots(1, -1) {}
+  std::vector<short> roots; // unless multiroot trees are supported, this
+                            // will have a single member
+  std::vector<std::pair<short, short> > h_m_pairs;
+};
+
+class ArcFactoredForest {
+ public:
+  explicit ArcFactoredForest(short num_words) :
+      num_words_(num_words),
+      root_edges_(num_words),
+      edges_(num_words, num_words) {
+    for (int h = 0; h < num_words; ++h) {
+      for (int m = 0; m < num_words; ++m) {
+        edges_(h, m).h = h + 1;
+        edges_(h, m).m = m + 1;
+      }
+      root_edges_[h].h = 0;
+      root_edges_[h].m = h + 1;
+    }
+  }
+
+  // compute the maximum spanning tree based on the current weighting
+  // using the O(n^2) CLE algorithm
+  void MaximumSpanningTree(SpanningTree* st) const;
+
+  struct Edge {
+    Edge() : h(), m(), features(), edge_prob(prob_t::Zero()) {}
+    short h;
+    short m;
+    SparseVector<weight_t> features;
+    prob_t edge_prob;
+  };
+
+  const Edge& operator()(short h, short m) const {
+    assert(m > 0);
+    assert(m <= num_words_);
+    assert(h >= 0);
+    assert(h <= num_words_);
+    return h ? edges_(h - 1, m - 1) : root_edges_[m - 1];
+  }
+
+  Edge& operator()(short h, short m) {
+    assert(m > 0);
+    assert(m <= num_words_);
+    assert(h >= 0);
+    assert(h <= num_words_);
+    return h ? edges_(h - 1, m - 1) : root_edges_[m - 1];
+  }
+
+  template <class V>
+  void Reweight(const V& weights) {
+    for (int m = 0; m < num_words_; ++m) {
+      for (int h = 0; h < num_words_; ++h) {
+        if (h != m) {
+          Edge& e = edges_(h, m);
+          e.edge_prob.logeq(e.features.dot(weights));
+        }
+      }
+      Edge& e = root_edges_[m];
+      e.edge_prob.logeq(e.features.dot(weights));
+    }
+  }
+
+ private:
+  unsigned num_words_;
+  std::vector<Edge> root_edges_;
+  Array2D<Edge> edges_;
+};
+
+inline std::ostream& operator<<(std::ostream& os, const ArcFactoredForest::Edge& edge) {
+  return os << "(" << edge.h << " < " << edge.m << ")";
+}
+
+#endif