1 files changed, 130 insertions, 0 deletions
diff --git a/decoder/viterbi.h b/decoder/viterbi.h
new file mode 100644
index 00000000..46a4f528
--- /dev/null
+++ b/decoder/viterbi.h
@@ -0,0 +1,130 @@
+#ifndef _VITERBI_H_
+#define _VITERBI_H_
+
+#include <vector>
+#include "prob.h"
+#include "hg.h"
+#include "tdict.h"
+
+// V must implement:
+//  void operator()(const vector<const T*>& ants, T* result);
+template<typename T, typename Traversal, typename WeightType, typename WeightFunction>
+WeightType Viterbi(const Hypergraph& hg,
+                   T* result,
+                   const Traversal& traverse = Traversal(),
+                   const WeightFunction& weight = WeightFunction()) {
+  const int num_nodes = hg.nodes_.size();
+  std::vector<T> vit_result(num_nodes);
+  std::vector<WeightType> vit_weight(num_nodes, WeightType::Zero());
+
+  for (int i = 0; i < num_nodes; ++i) {
+    const Hypergraph::Node& cur_node = hg.nodes_[i];
+    WeightType* const cur_node_best_weight = &vit_weight[i];
+    T*          const cur_node_best_result = &vit_result[i];
+    
+    const int num_in_edges = cur_node.in_edges_.size();
+    if (num_in_edges == 0) {
+      *cur_node_best_weight = WeightType(1);
+      continue;
+    }
+    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) {
+        *cur_node_best_weight = score;
+        traverse(edge, ants, cur_node_best_result);
+      }
+    }
+  }
+  std::swap(*result, vit_result.back());
+  return vit_weight.back();
+}
+
+struct PathLengthTraversal {
+  void operator()(const Hypergraph::Edge& edge,
+                  const std::vector<const int*>& ants,
+                  int* result) const {
+    (void) edge;
+    *result = 1;
+    for (int i = 0; i < ants.size(); ++i) *result += *ants[i];
+  }
+};
+
+struct ESentenceTraversal {
+  void operator()(const Hypergraph::Edge& edge,
+                  const std::vector<const std::vector<WordID>*>& ants,
+                  std::vector<WordID>* result) const {
+    edge.rule_->ESubstitute(ants, result);
+  }
+};
+
+struct ELengthTraversal {
+  void operator()(const Hypergraph::Edge& edge,
+                  const std::vector<const int*>& ants,
+                  int* result) const {
+    *result = edge.rule_->ELength() - edge.rule_->Arity();
+    for (int i = 0; i < ants.size(); ++i) *result += *ants[i];
+  }
+};
+
+struct FSentenceTraversal {
+  void operator()(const Hypergraph::Edge& edge,
+                  const std::vector<const std::vector<WordID>*>& ants,
+                  std::vector<WordID>* result) const {
+    edge.rule_->FSubstitute(ants, result);
+  }
+};
+
+// create a strings of the form (S (X the man) (X said (X he (X would (X go)))))
+struct ETreeTraversal {
+  ETreeTraversal() : left("("), space(" "), right(")") {}
+  const std::string left;
+  const std::string space;
+  const std::string right;
+  void operator()(const Hypergraph::Edge& edge,
+                  const std::vector<const std::vector<WordID>*>& ants,
+                  std::vector<WordID>* result) const {
+    std::vector<WordID> tmp;
+    edge.rule_->ESubstitute(ants, &tmp);
+    const std::string cat = TD::Convert(edge.rule_->GetLHS() * -1);
+    if (cat == "Goal")
+      result->swap(tmp);
+    else
+      TD::ConvertSentence(left + cat + space + TD::GetString(tmp) + right,
+                          result);
+  }
+};
+
+struct FTreeTraversal {
+  FTreeTraversal() : left("("), space(" "), right(")") {}
+  const std::string left;
+  const std::string space;
+  const std::string right;
+  void operator()(const Hypergraph::Edge& edge,
+                  const std::vector<const std::vector<WordID>*>& ants,
+                  std::vector<WordID>* result) const {
+    std::vector<WordID> tmp;
+    edge.rule_->FSubstitute(ants, &tmp);
+    const std::string cat = TD::Convert(edge.rule_->GetLHS() * -1);
+    if (cat == "Goal")
+      result->swap(tmp);
+    else
+      TD::ConvertSentence(left + cat + space + TD::GetString(tmp) + right,
+                          result);
+  }
+};
+
+prob_t ViterbiESentence(const Hypergraph& hg, std::vector<WordID>* result);
+std::string ViterbiETree(const Hypergraph& hg);
+prob_t ViterbiFSentence(const Hypergraph& hg, std::vector<WordID>* result);
+std::string ViterbiFTree(const Hypergraph& hg);
+int ViterbiELength(const Hypergraph& hg);
+int ViterbiPathLength(const Hypergraph& hg);
+
+#endif