1 files changed, 58 insertions, 0 deletions
diff --git a/decoder/hg_union.cc b/decoder/hg_union.cc
new file mode 100644
index 00000000..37082976
--- /dev/null
+++ b/decoder/hg_union.cc
@@ -0,0 +1,58 @@
+#include "hg_union.h"
+
+#include "hg.h"
+
+using namespace std;
+
+namespace HG {
+
+void Union(const Hypergraph& in, Hypergraph* out) {
+  if (&in == out) return;
+  if (out->nodes_.empty()) {
+    out->nodes_ = in.nodes_;
+    out->edges_ = in.edges_; return;
+  }
+  unsigned noff = out->nodes_.size();
+  unsigned eoff = out->edges_.size();
+  int ogoal = in.nodes_.size() - 1;
+  int cgoal = noff - 1;
+  // keep a single goal node, so add nodes.size - 1
+  out->nodes_.resize(out->nodes_.size() + ogoal);
+  // add all edges
+  out->edges_.resize(out->edges_.size() + in.edges_.size());
+
+  for (int i = 0; i < ogoal; ++i) {
+    const Hypergraph::Node& on = in.nodes_[i];
+    Hypergraph::Node& cn = out->nodes_[i + noff];
+    cn.id_ = i + noff;
+    cn.in_edges_.resize(on.in_edges_.size());
+    for (unsigned j = 0; j < on.in_edges_.size(); ++j)
+      cn.in_edges_[j] = on.in_edges_[j] + eoff;
+
+    cn.out_edges_.resize(on.out_edges_.size());
+    for (unsigned j = 0; j < on.out_edges_.size(); ++j)
+      cn.out_edges_[j] = on.out_edges_[j] + eoff;
+  }
+
+  for (unsigned i = 0; i < in.edges_.size(); ++i) {
+    const Hypergraph::Edge& oe = in.edges_[i];
+    Hypergraph::Edge& ce = out->edges_[i + eoff];
+    ce.id_ = i + eoff;
+    ce.rule_ = oe.rule_;
+    ce.feature_values_ = oe.feature_values_;
+    if (oe.head_node_ == ogoal) {
+      ce.head_node_ = cgoal;
+      out->nodes_[cgoal].in_edges_.push_back(ce.id_);
+    } else {
+      ce.head_node_ = oe.head_node_ + noff;
+    }
+    ce.tail_nodes_.resize(oe.tail_nodes_.size());
+    for (unsigned j = 0; j < oe.tail_nodes_.size(); ++j)
+      ce.tail_nodes_[j] = oe.tail_nodes_[j] + noff;
+  }
+
+  out->TopologicallySortNodesAndEdges(cgoal);
+}
+
+}
+