compute viterbi result once only per node (for best edge)

git-svn-id: https://ws10smt.googlecode.com/svn/trunk@182 ec762483-ff6d-05da-a07a-a48fb63a330f

2 files changed, 12 insertions, 8 deletions

diff --git a/decoder/cdec.cc b/decoder/cdec.cc
index bb29bafb..b43b7826 100644
--- a/decoder/cdec.cc
+++ b/decoder/cdec.cc
@@ -86,6 +86,7 @@ void InitCommandLine(int argc, char** argv, po::variables_map* conf) {
         ("show_expected_length", "Show the expected translation length under the model")
         ("show_partition,z", "Compute and show the partition (inside score)")
         ("show_cfg_search_space", "Show the search space as a CFG")
+    ("show_viterbi_features","Show the feature vector for the viterbi translation")
     ("prelm_density_prune", po::value<double>(), "Applied to -LM forest just before final LM rescoring: keep no more than this many times the number of edges used in the best derivation tree (>=1.0)")
     ("density_prune", po::value<double>(), "Keep no more than this many times the number of edges used in the best derivation tree (>=1.0)")
         ("prelm_beam_prune", po::value<double>(), "Prune paths from -LM forest before LM rescoring, keeping paths within exp(alpha>=0)")
diff --git a/decoder/viterbi.h b/decoder/viterbi.h
index d4a97516..6b8bbed1 100644
--- a/decoder/viterbi.h
+++ b/decoder/viterbi.h
@@ -29,20 +29,23 @@ WeightType Viterbi(const Hypergraph& hg,
       *cur_node_best_weight = WeightType(1);
       continue;
     }
+    Hypergraph::Edge const* edge_best=0;
     for (int j = 0; j < num_in_edges; ++j) {
       const Hypergraph::Edge& edge = hg.edges_[cur_node.in_edges_[j]];
       WeightType score = weight(edge);
-      std::vector<const T*> ants(edge.tail_nodes_.size());
-      for (int k = 0; k < edge.tail_nodes_.size(); ++k) {
-        const int tail_node_index = edge.tail_nodes_[k];
-        score *= vit_weight[tail_node_index];
-        ants[k] = &vit_result[tail_node_index];
-      }
-      if (*cur_node_best_weight < score) {
+      for (int k = 0; k < edge.tail_nodes_.size(); ++k)
+        score *= vit_weight[edge.tail_nodes_[k]];
+      if (!edge_best || *cur_node_best_weight < score) {
         *cur_node_best_weight = score;
-        traverse(edge, ants, cur_node_best_result);
+        edge_best=&edge;
       }
     }
+    assert(edge_best);
+    Hypergraph::Edge const& edgeb=*edge_best;
+    std::vector<const T*> antsb(edgeb.tail_nodes_.size());
+    for (int k = 0; k < edgeb.tail_nodes_.size(); ++k)
+      antsb[k] = &vit_result[edgeb.tail_nodes_[k]];
+    traverse(edgeb, antsb, cur_node_best_result);
   }
   std::swap(*result, vit_result.back());
   return vit_weight.back();