Update incremental search

21 files changed, 467 insertions, 353 deletions

diff --git a/search/Jamfile b/search/Jamfile
index c00d23828..f6433e0e3 100644
--- a/search/Jamfile
+++ b/search/Jamfile
@@ -1,5 +1 @@
-fakelib search : weights.cc vertex.cc vertex_generator.cc edge_generator.cc rule.cc ../lm//kenlm ../util//kenutil /top//boost_system : : : <include>.. ;
-
-import testing ;
-
-unit-test weights_test : weights_test.cc search /top//boost_unit_test_framework ;
+fakelib search : edge_generator.cc nbest.cc rule.cc vertex.cc vertex_generator.cc ../lm//kenlm ../util//kenutil /top//boost_system : : : <include>.. ;
diff --git a/search/applied.hh b/search/applied.hh
new file mode 100644
index 000000000..bd659e5c0
--- /dev/null
+++ b/search/applied.hh
@@ -0,0 +1,86 @@
+#ifndef SEARCH_APPLIED__
+#define SEARCH_APPLIED__
+
+#include "search/edge.hh"
+#include "search/header.hh"
+#include "util/pool.hh"
+
+#include <math.h>
+
+namespace search {
+
+// A full hypothesis: a score, arity of the rule, a pointer to the decoder's rule (Note), and pointers to non-terminals that were substituted.  
+template <class Below> class GenericApplied : public Header {
+  public:
+    GenericApplied() {}
+
+    GenericApplied(void *location, PartialEdge partial) 
+      : Header(location) {
+      memcpy(Base(), partial.Base(), kHeaderSize);
+      Below *child_out = Children();
+      const PartialVertex *part = partial.NT();
+      const PartialVertex *const part_end_loop = part + partial.GetArity();
+      for (; part != part_end_loop; ++part, ++child_out)
+        *child_out = Below(part->End());
+    }
+    
+    GenericApplied(void *location, Score score, Arity arity, Note note) : Header(location, arity) {
+      SetScore(score);
+      SetNote(note);
+    }
+
+    explicit GenericApplied(History from) : Header(from) {}
+
+
+    // These are arrays of length GetArity().
+    Below *Children() {
+      return reinterpret_cast<Below*>(After());
+    }
+    const Below *Children() const {
+      return reinterpret_cast<const Below*>(After());
+    }
+
+    static std::size_t Size(Arity arity) {
+      return kHeaderSize + arity * sizeof(const Below);
+    }
+};
+
+// Applied rule that references itself.  
+class Applied : public GenericApplied<Applied> {
+  private:
+    typedef GenericApplied<Applied> P;
+
+  public:
+    Applied() {}
+    Applied(void *location, PartialEdge partial) : P(location, partial) {}
+    Applied(History from) : P(from) {}
+};
+
+// How to build single-best hypotheses.  
+class SingleBest {
+  public:
+    typedef PartialEdge Combine;
+
+    void Add(PartialEdge &existing, PartialEdge add) const {
+      if (!existing.Valid() || existing.GetScore() < add.GetScore())
+        existing = add;
+    }
+
+    NBestComplete Complete(PartialEdge partial) {
+      if (!partial.Valid()) 
+        return NBestComplete(NULL, lm::ngram::ChartState(), -INFINITY);
+      void *place_final = pool_.Allocate(Applied::Size(partial.GetArity()));
+      Applied(place_final, partial);
+      return NBestComplete(
+          place_final,
+          partial.CompletedState(),
+          partial.GetScore());
+    }
+
+  private:
+    util::Pool pool_;
+};
+
+} // namespace search
+
+#endif // SEARCH_APPLIED__
diff --git a/search/config.hh b/search/config.hh
index ef8e2354a..ba18c09e9 100644
--- a/search/config.hh
+++ b/search/config.hh
@@ -1,23 +1,36 @@
 #ifndef SEARCH_CONFIG__
 #define SEARCH_CONFIG__
 
-#include "search/weights.hh"
-#include "util/string_piece.hh"
+#include "search/types.hh"
 
 namespace search {
 
+struct NBestConfig {
+  explicit NBestConfig(unsigned int in_size) {
+    keep = in_size;
+    size = in_size;
+  }
+  
+  unsigned int keep, size;
+};
+
 class Config {
   public:
-    Config(const Weights &weights, unsigned int pop_limit) :
-      weights_(weights), pop_limit_(pop_limit) {}
+    Config(Score lm_weight, unsigned int pop_limit, const NBestConfig &nbest) :
+      lm_weight_(lm_weight), pop_limit_(pop_limit), nbest_(nbest) {}
 
-    const Weights &GetWeights() const { return weights_; }
+    Score LMWeight() const { return lm_weight_; }
 
     unsigned int PopLimit() const { return pop_limit_; }
 
+    const NBestConfig &GetNBest() const { return nbest_; }
+
   private:
-    Weights weights_;
+    Score lm_weight_;
+
     unsigned int pop_limit_;
+
+    NBestConfig nbest_;
 };
 
 } // namespace search
diff --git a/search/context.hh b/search/context.hh
index 62163144f..08f21bbf0 100644
--- a/search/context.hh
+++ b/search/context.hh
@@ -1,30 +1,16 @@
 #ifndef SEARCH_CONTEXT__
 #define SEARCH_CONTEXT__
 
-#include "lm/model.hh"
 #include "search/config.hh"
-#include "search/final.hh"
-#include "search/types.hh"
 #include "search/vertex.hh"
-#include "util/exception.hh"
-#include "util/pool.hh"
 
 #include <boost/pool/object_pool.hpp>
-#include <boost/ptr_container/ptr_vector.hpp>
-
-#include <vector>
 
 namespace search {
 
-class Weights;
-
 class ContextBase {
   public:
-    explicit ContextBase(const Config &config) : pop_limit_(config.PopLimit()), weights_(config.GetWeights()) {}
-
-    util::Pool &FinalPool() {
-      return final_pool_;
-    }
+    explicit ContextBase(const Config &config) : config_(config) {}
 
     VertexNode *NewVertexNode() {
       VertexNode *ret = vertex_node_pool_.construct();
@@ -36,18 +22,16 @@ class ContextBase {
       vertex_node_pool_.destroy(node);
     }
 
-    unsigned int PopLimit() const { return pop_limit_; }
+    unsigned int PopLimit() const { return config_.PopLimit(); }
 
-    const Weights &GetWeights() const { return weights_; }
+    Score LMWeight() const { return config_.LMWeight(); }
 
-  private:
-    util::Pool final_pool_;
+    const Config &GetConfig() const { return config_; }
 
+  private:
     boost::object_pool<VertexNode> vertex_node_pool_;
 
-    unsigned int pop_limit_;
-
-    const Weights &weights_;
+    Config config_;
 };
 
 template <class Model> class Context : public ContextBase {
diff --git a/search/edge_generator.cc b/search/edge_generator.cc
index 260159b1f..eacf5de5c 100644
--- a/search/edge_generator.cc
+++ b/search/edge_generator.cc
@@ -1,6 +1,7 @@
 #include "search/edge_generator.hh"
 
 #include "lm/left.hh"
+#include "lm/model.hh"
 #include "lm/partial.hh"
 #include "search/context.hh"
 #include "search/vertex.hh"
@@ -38,7 +39,7 @@ template <class Model> void FastScore(const Context<Model> &context, Arity victi
       *cover = *(cover + 1);
     }
   }
-  update.SetScore(update.GetScore() + adjustment * context.GetWeights().LM());
+  update.SetScore(update.GetScore() + adjustment * context.LMWeight());
 }
 
 } // namespace
diff --git a/search/edge_generator.hh b/search/edge_generator.hh
index 582c78b7b..203942c6f 100644
--- a/search/edge_generator.hh
+++ b/search/edge_generator.hh
@@ -2,7 +2,6 @@
 #define SEARCH_EDGE_GENERATOR__
 
 #include "search/edge.hh"
-#include "search/note.hh"
 #include "search/types.hh"
 
 #include <queue>
diff --git a/search/final.hh b/search/final.hh
deleted file mode 100644
index 50e62cf2e..000000000
--- a/search/final.hh
+++ /dev/null
@@ -1,36 +0,0 @@
-#ifndef SEARCH_FINAL__
-#define SEARCH_FINAL__
-
-#include "search/header.hh"
-#include "util/pool.hh"
-
-namespace search {
-
-// A full hypothesis with pointers to children.
-class Final : public Header {
-  public:
-    Final() {}
-
-    Final(util::Pool &pool, Score score, Arity arity, Note note) 
-      : Header(pool.Allocate(Size(arity)), arity) {
-      SetScore(score);
-      SetNote(note);
-    }
-
-    // These are arrays of length GetArity().
-    Final *Children() {
-      return reinterpret_cast<Final*>(After());
-    }
-    const Final *Children() const {
-      return reinterpret_cast<const Final*>(After());
-    }
-
-  private:
-    static std::size_t Size(Arity arity) {
-      return kHeaderSize + arity * sizeof(const Final);
-    }
-};
-
-} // namespace search
-
-#endif // SEARCH_FINAL__
diff --git a/search/header.hh b/search/header.hh
index 25550dbed..69f0eed04 100644
--- a/search/header.hh
+++ b/search/header.hh
@@ -3,7 +3,6 @@
 
 // Header consisting of Score, Arity, and Note
 
-#include "search/note.hh"
 #include "search/types.hh"
 
 #include <stdint.h>
@@ -24,6 +23,9 @@ class Header {
     bool operator<(const Header &other) const {
       return GetScore() < other.GetScore();
     }
+    bool operator>(const Header &other) const {
+      return GetScore() > other.GetScore();
+    }
 
     Arity GetArity() const {
       return *reinterpret_cast<const Arity*>(base_ + sizeof(Score));
@@ -36,9 +38,14 @@ class Header {
       *reinterpret_cast<Note*>(base_ + sizeof(Score) + sizeof(Arity)) = to;
     }
 
+    uint8_t *Base() { return base_; }
+    const uint8_t *Base() const { return base_; }
+
   protected:
     Header() : base_(NULL) {}
 
+    explicit Header(void *base) : base_(static_cast<uint8_t*>(base)) {}
+
     Header(void *base, Arity arity) : base_(static_cast<uint8_t*>(base)) {
       *reinterpret_cast<Arity*>(base_ + sizeof(Score)) = arity;
     }
diff --git a/search/nbest.cc b/search/nbest.cc
new file mode 100644
index 000000000..ec3322c97
--- /dev/null
+++ b/search/nbest.cc
@@ -0,0 +1,106 @@
+#include "search/nbest.hh"
+
+#include "util/pool.hh"
+
+#include <algorithm>
+#include <functional>
+#include <queue>
+
+#include <assert.h>
+#include <math.h>
+
+namespace search {
+
+NBestList::NBestList(std::vector<PartialEdge> &partials, util::Pool &entry_pool, std::size_t keep) {
+  assert(!partials.empty());
+  std::vector<PartialEdge>::iterator end;
+  if (partials.size() > keep) {
+    end = partials.begin() + keep;
+    std::nth_element(partials.begin(), end, partials.end(), std::greater<PartialEdge>());
+  } else {
+    end = partials.end();
+  }
+  for (std::vector<PartialEdge>::const_iterator i(partials.begin()); i != end; ++i) {
+    queue_.push(QueueEntry(entry_pool.Allocate(QueueEntry::Size(i->GetArity())), *i));
+  }
+}
+
+Score NBestList::TopAfterConstructor() const {
+  assert(revealed_.empty());
+  return queue_.top().GetScore();
+}
+
+const std::vector<Applied> &NBestList::Extract(util::Pool &pool, std::size_t n) {
+  while (revealed_.size() < n && !queue_.empty()) {
+    MoveTop(pool);
+  }
+  return revealed_;
+}
+
+Score NBestList::Visit(util::Pool &pool, std::size_t index) {
+  if (index + 1 < revealed_.size())
+    return revealed_[index + 1].GetScore() - revealed_[index].GetScore();
+  if (queue_.empty()) 
+    return -INFINITY;
+  if (index + 1 == revealed_.size())
+    return queue_.top().GetScore() - revealed_[index].GetScore();
+  assert(index == revealed_.size());
+
+  MoveTop(pool);
+
+  if (queue_.empty()) return -INFINITY;
+  return queue_.top().GetScore() - revealed_[index].GetScore();
+}
+
+Applied NBestList::Get(util::Pool &pool, std::size_t index) {
+  assert(index <= revealed_.size());
+  if (index == revealed_.size()) MoveTop(pool);
+  return revealed_[index];
+}
+
+void NBestList::MoveTop(util::Pool &pool) {
+  assert(!queue_.empty());
+  QueueEntry entry(queue_.top());
+  queue_.pop();
+  RevealedRef *const children_begin = entry.Children();
+  RevealedRef *const children_end = children_begin + entry.GetArity();
+  Score basis = entry.GetScore();
+  for (RevealedRef *child = children_begin; child != children_end; ++child) {
+    Score change = child->in_->Visit(pool, child->index_);
+    if (change != -INFINITY) {
+      assert(change < 0.001);
+      QueueEntry new_entry(pool.Allocate(QueueEntry::Size(entry.GetArity())), basis + change, entry.GetArity(), entry.GetNote());
+      std::copy(children_begin, child, new_entry.Children());
+      RevealedRef *update = new_entry.Children() + (child - children_begin);
+      update->in_ = child->in_;
+      update->index_ = child->index_ + 1;
+      std::copy(child + 1, children_end, update + 1);
+      queue_.push(new_entry);
+    }
+    // Gesmundo, A. and Henderson, J. Faster Cube Pruning, IWSLT 2010.
+    if (child->index_) break;
+  }
+
+  // Convert QueueEntry to Applied.  This leaves some unused memory.  
+  void *overwrite = entry.Children();
+  for (unsigned int i = 0; i < entry.GetArity(); ++i) {
+    RevealedRef from(*(static_cast<const RevealedRef*>(overwrite) + i));
+    *(static_cast<Applied*>(overwrite) + i) = from.in_->Get(pool, from.index_);
+  }
+  revealed_.push_back(Applied(entry.Base()));
+}
+
+NBestComplete NBest::Complete(std::vector<PartialEdge> &partials) {
+  assert(!partials.empty());
+  NBestList *list = list_pool_.construct(partials, entry_pool_, config_.keep);
+  return NBestComplete(
+      list,
+      partials.front().CompletedState(), // All partials have the same state
+      list->TopAfterConstructor());
+}
+
+const std::vector<Applied> &NBest::Extract(History history) {
+  return static_cast<NBestList*>(history)->Extract(entry_pool_, config_.size);
+}
+
+} // namespace search
diff --git a/search/nbest.hh b/search/nbest.hh
new file mode 100644
index 000000000..cb7651bc2
--- /dev/null
+++ b/search/nbest.hh
@@ -0,0 +1,81 @@
+#ifndef SEARCH_NBEST__
+#define SEARCH_NBEST__
+
+#include "search/applied.hh"
+#include "search/config.hh"
+#include "search/edge.hh"
+
+#include <boost/pool/object_pool.hpp>
+
+#include <cstddef>
+#include <queue>
+#include <vector>
+
+#include <assert.h>
+
+namespace search {
+
+class NBestList;
+
+class NBestList {
+  private:
+    class RevealedRef {
+      public: 
+        explicit RevealedRef(History history) 
+          : in_(static_cast<NBestList*>(history)), index_(0) {}
+
+      private:
+        friend class NBestList;
+
+        NBestList *in_;
+        std::size_t index_;
+    };
+    
+    typedef GenericApplied<RevealedRef> QueueEntry;
+
+  public:
+    NBestList(std::vector<PartialEdge> &existing, util::Pool &entry_pool, std::size_t keep);
+
+    Score TopAfterConstructor() const;
+
+    const std::vector<Applied> &Extract(util::Pool &pool, std::size_t n);
+
+  private:
+    Score Visit(util::Pool &pool, std::size_t index);
+
+    Applied Get(util::Pool &pool, std::size_t index);
+
+    void MoveTop(util::Pool &pool);
+
+    typedef std::vector<Applied> Revealed;
+    Revealed revealed_;
+
+    typedef std::priority_queue<QueueEntry> Queue;
+    Queue queue_;
+};
+
+class NBest {
+  public:
+    typedef std::vector<PartialEdge> Combine;
+
+    explicit NBest(const NBestConfig &config) : config_(config) {}
+
+    void Add(std::vector<PartialEdge> &existing, PartialEdge addition) const {
+      existing.push_back(addition);
+    }
+
+    NBestComplete Complete(std::vector<PartialEdge> &partials);
+
+    const std::vector<Applied> &Extract(History root);
+
+  private:
+    const NBestConfig config_;
+
+    boost::object_pool<NBestList> list_pool_;
+
+    util::Pool entry_pool_;
+};
+
+} // namespace search
+
+#endif // SEARCH_NBEST__
diff --git a/search/note.hh b/search/note.hh
deleted file mode 100644
index 50bed06ec..000000000
--- a/search/note.hh
+++ /dev/null
@@ -1,12 +0,0 @@
-#ifndef SEARCH_NOTE__
-#define SEARCH_NOTE__
-
-namespace search {
-
-union Note {
-  const void *vp;
-};
-
-} // namespace search
-
-#endif // SEARCH_NOTE__
diff --git a/search/rule.cc b/search/rule.cc
index 5b00207ef..0244a09f7 100644
--- a/search/rule.cc
+++ b/search/rule.cc
@@ -1,7 +1,7 @@
 #include "search/rule.hh"
 
+#include "lm/model.hh"
 #include "search/context.hh"
-#include "search/final.hh"
 
 #include <ostream>
 
@@ -9,35 +9,35 @@
 
 namespace search {
 
-template <class Model> float ScoreRule(const Context<Model> &context, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing) {
-  unsigned int oov_count = 0;
-  float prob = 0.0;
-  const Model &model = context.LanguageModel();
-  const lm::WordIndex oov = model.GetVocabulary().NotFound();
-  for (std::vector<lm::WordIndex>::const_iterator word = words.begin(); ; ++word) {
-    lm::ngram::RuleScore<Model> scorer(model, *(writing++));
-    // TODO: optimize
-    if (prepend_bos && (word == words.begin())) {
-      scorer.BeginSentence();
-    }
-    for (; ; ++word) {
-      if (word == words.end()) {
-        prob += scorer.Finish();
-        return static_cast<float>(oov_count) * context.GetWeights().OOV() + prob * context.GetWeights().LM();
-      }
-      if (*word == kNonTerminal) break;
-      if (*word == oov) ++oov_count;
+template <class Model> ScoreRuleRet ScoreRule(const Model &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing) {
+  ScoreRuleRet ret;
+  ret.prob = 0.0;
+  ret.oov = 0;
+  const lm::WordIndex oov = model.GetVocabulary().NotFound(), bos = model.GetVocabulary().BeginSentence();
+  lm::ngram::RuleScore<Model> scorer(model, *(writing++));
+  std::vector<lm::WordIndex>::const_iterator word = words.begin();
+  if (word != words.end() && *word == bos) {
+    scorer.BeginSentence();
+    ++word;
+  }
+  for (; word != words.end(); ++word) {
+    if (*word == kNonTerminal) {
+      ret.prob += scorer.Finish();
+      scorer.Reset(*(writing++));
+    } else {
+      if (*word == oov) ++ret.oov;
       scorer.Terminal(*word);
     }
-    prob += scorer.Finish();
   }
+  ret.prob += scorer.Finish();
+  return ret;
 }
 
-template float ScoreRule(const Context<lm::ngram::RestProbingModel> &model, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing);
-template float ScoreRule(const Context<lm::ngram::ProbingModel> &model, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing);
-template float ScoreRule(const Context<lm::ngram::TrieModel> &model, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing);
-template float ScoreRule(const Context<lm::ngram::QuantTrieModel> &model, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing);
-template float ScoreRule(const Context<lm::ngram::ArrayTrieModel> &model, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing);
-template float ScoreRule(const Context<lm::ngram::QuantArrayTrieModel> &model, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *writing);
+template ScoreRuleRet ScoreRule(const lm::ngram::RestProbingModel &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing);
+template ScoreRuleRet ScoreRule(const lm::ngram::ProbingModel &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing);
+template ScoreRuleRet ScoreRule(const lm::ngram::TrieModel &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing);
+template ScoreRuleRet ScoreRule(const lm::ngram::QuantTrieModel &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing);
+template ScoreRuleRet ScoreRule(const lm::ngram::ArrayTrieModel &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing);
+template ScoreRuleRet ScoreRule(const lm::ngram::QuantArrayTrieModel &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *writing);
 
 } // namespace search
diff --git a/search/rule.hh b/search/rule.hh
index 0ce2794db..43ca61625 100644
--- a/search/rule.hh
+++ b/search/rule.hh
@@ -9,11 +9,16 @@
 
 namespace search {
 
-template <class Model> class Context;
-
 const lm::WordIndex kNonTerminal = lm::kMaxWordIndex;
 
-template <class Model> float ScoreRule(const Context<Model> &context, const std::vector<lm::WordIndex> &words, bool prepend_bos, lm::ngram::ChartState *state_out);
+struct ScoreRuleRet {
+  Score prob;
+  unsigned int oov;
+};
+
+// Pass <s> and </s> normally.  
+// Indicate non-terminals with kNonTerminal.  
+template <class Model> ScoreRuleRet ScoreRule(const Model &model, const std::vector<lm::WordIndex> &words, lm::ngram::ChartState *state_out);
 
 } // namespace search
 
diff --git a/search/types.hh b/search/types.hh
index 06eb5bfa2..f9c849b3f 100644
--- a/search/types.hh
+++ b/search/types.hh
@@ -3,12 +3,29 @@
 
 #include <stdint.h>
 
+namespace lm { namespace ngram { class ChartState; } }
+
 namespace search {
 
 typedef float Score;
 
 typedef uint32_t Arity;
 
+union Note {
+  const void *vp;
+};
+
+typedef void *History;
+
+struct NBestComplete {
+  NBestComplete(History in_history, const lm::ngram::ChartState &in_state, Score in_score) 
+    : history(in_history), state(&in_state), score(in_score) {}
+
+  History history;
+  const lm::ngram::ChartState *state;
+  Score score;
+};
+
 } // namespace search
 
 #endif // SEARCH_TYPES__
diff --git a/search/vertex.cc b/search/vertex.cc
index 11f4631fa..45842982c 100644
--- a/search/vertex.cc
+++ b/search/vertex.cc
@@ -19,21 +19,34 @@ struct GreaterByBound : public std::binary_function<const VertexNode *, const Ve
 
 } // namespace
 
-void VertexNode::SortAndSet(ContextBase &context, VertexNode **parent_ptr) {
+void VertexNode::RecursiveSortAndSet(ContextBase &context, VertexNode *&parent_ptr) {
   if (Complete()) {
-    assert(end_.Valid());
+    assert(end_);
     assert(extend_.empty());
-    bound_ = end_.GetScore();
     return;
   }
-  if (extend_.size() == 1 && parent_ptr) {
-    *parent_ptr = extend_[0];
-    extend_[0]->SortAndSet(context, parent_ptr);
+  if (extend_.size() == 1) {
+    parent_ptr = extend_[0];
+    extend_[0]->RecursiveSortAndSet(context, parent_ptr);
     context.DeleteVertexNode(this);
     return;
   }
   for (std::vector<VertexNode*>::iterator i = extend_.begin(); i != extend_.end(); ++i) {
-    (*i)->SortAndSet(context, &*i);
+    (*i)->RecursiveSortAndSet(context, *i);
+  }
+  std::sort(extend_.begin(), extend_.end(), GreaterByBound());
+  bound_ = extend_.front()->Bound();
+}
+
+void VertexNode::SortAndSet(ContextBase &context) {
+  // This is the root.  The root might be empty.  
+  if (extend_.empty()) {
+    bound_ = -INFINITY;
+    return;
+  }
+  // The root cannot be replaced.  There's always one transition.  
+  for (std::vector<VertexNode*>::iterator i = extend_.begin(); i != extend_.end(); ++i) {
+    (*i)->RecursiveSortAndSet(context, *i);
   }
   std::sort(extend_.begin(), extend_.end(), GreaterByBound());
   bound_ = extend_.front()->Bound();
diff --git a/search/vertex.hh b/search/vertex.hh
index 52bc1dfe7..10b3339b9 100644
--- a/search/vertex.hh
+++ b/search/vertex.hh
@@ -2,7 +2,6 @@
 #define SEARCH_VERTEX__
 
 #include "lm/left.hh"
-#include "search/final.hh"
 #include "search/types.hh"
 
 #include <boost/unordered_set.hpp>
@@ -10,6 +9,7 @@
 #include <queue>
 #include <vector>
 
+#include <math.h>
 #include <stdint.h>
 
 namespace search {
@@ -18,7 +18,7 @@ class ContextBase;
 
 class VertexNode {
   public:
-    VertexNode() {}
+    VertexNode() : end_() {}
 
     void InitRoot() {
       extend_.clear();
@@ -26,7 +26,7 @@ class VertexNode {
       state_.left.length = 0;
       state_.right.length = 0;
       right_full_ = false;
-      end_ = Final();
+      end_ = History();
     }
 
     lm::ngram::ChartState &MutableState() { return state_; }
@@ -36,20 +36,21 @@ class VertexNode {
       extend_.push_back(next);
     }
 
-    void SetEnd(Final end) {
-      assert(!end_.Valid());
+    void SetEnd(History end, Score score) {
+      assert(!end_);
       end_ = end;
+      bound_ = score;
     }
     
-    void SortAndSet(ContextBase &context, VertexNode **parent_pointer);
+    void SortAndSet(ContextBase &context);
 
     // Should only happen to a root node when the entire vertex is empty.   
     bool Empty() const {
-      return !end_.Valid() && extend_.empty();
+      return !end_ && extend_.empty();
     }
 
     bool Complete() const {
-      return end_.Valid();
+      return end_;
     }
 
     const lm::ngram::ChartState &State() const { return state_; }
@@ -64,7 +65,7 @@ class VertexNode {
     }
 
     // Will be invalid unless this is a leaf.   
-    const Final End() const { return end_; }
+    const History End() const { return end_; }
 
     const VertexNode &operator[](size_t index) const {
       return *extend_[index];
@@ -75,13 +76,15 @@ class VertexNode {
     }
 
   private:
+    void RecursiveSortAndSet(ContextBase &context, VertexNode *&parent);
+
     std::vector<VertexNode*> extend_;
 
     lm::ngram::ChartState state_;
     bool right_full_;
 
     Score bound_;
-    Final end_;
+    History end_;
 };
 
 class PartialVertex {
@@ -97,7 +100,7 @@ class PartialVertex {
     const lm::ngram::ChartState &State() const { return back_->State(); }
     bool RightFull() const { return back_->RightFull(); }
 
-    Score Bound() const { return Complete() ? back_->End().GetScore() : (*back_)[index_].Bound(); }
+    Score Bound() const { return Complete() ? back_->Bound() : (*back_)[index_].Bound(); }
 
     unsigned char Length() const { return back_->Length(); }
 
@@ -121,7 +124,7 @@ class PartialVertex {
       return ret;
     }
 
-    const Final End() const {
+    const History End() const {
       return back_->End();
     }
 
@@ -130,16 +133,18 @@ class PartialVertex {
     unsigned int index_;
 };
 
+template <class Output> class VertexGenerator;
+
 class Vertex {
   public:
     Vertex() {}
 
     PartialVertex RootPartial() const { return PartialVertex(root_); }
 
-    const Final BestChild() const {
+    const History BestChild() const {
       PartialVertex top(RootPartial());
       if (top.Empty()) {
-        return Final();
+        return History();
       } else {
         PartialVertex continuation;
         while (!top.Complete()) {
@@ -150,8 +155,8 @@ class Vertex {
     }
 
   private:
-    friend class VertexGenerator;
-
+    template <class Output> friend class VertexGenerator;
+    template <class Output> friend class RootVertexGenerator;
     VertexNode root_;
 };
 
diff --git a/search/vertex_generator.cc b/search/vertex_generator.cc
index e18010c38..73139ffc5 100644
--- a/search/vertex_generator.cc
+++ b/search/vertex_generator.cc
@@ -11,23 +11,11 @@
 
 namespace search {
 
-VertexGenerator::VertexGenerator(ContextBase &context, Vertex &gen) : context_(context), gen_(gen) {
-  gen.root_.InitRoot();
-}
-
 #if BOOST_VERSION > 104200
 namespace {
 
 const uint64_t kCompleteAdd = static_cast<uint64_t>(-1);
 
-// Parallel structure to VertexNode.  
-struct Trie {
-  Trie() : under(NULL) {}
-
-  VertexNode *under;
-  boost::unordered_map<uint64_t, Trie> extend;
-};
-
 Trie &FindOrInsert(ContextBase &context, Trie &node, uint64_t added, const lm::ngram::ChartState &state, unsigned char left, bool left_full, unsigned char right, bool right_full) {
   Trie &next = node.extend[added];
   if (!next.under) {
@@ -43,19 +31,10 @@ Trie &FindOrInsert(ContextBase &context, Trie &node, uint64_t added, const lm::n
   return next;
 }
 
-void CompleteTransition(ContextBase &context, Trie &starter, PartialEdge partial) {
-  Final final(context.FinalPool(), partial.GetScore(), partial.GetArity(), partial.GetNote());
-  Final *child_out = final.Children();
-  const PartialVertex *part = partial.NT();
-  const PartialVertex *const part_end_loop = part + partial.GetArity();
-  for (; part != part_end_loop; ++part, ++child_out)
-    *child_out = part->End();
-
-  starter.under->SetEnd(final);
-}
+} // namespace
 
-void AddHypothesis(ContextBase &context, Trie &root, PartialEdge partial) {
-  const lm::ngram::ChartState &state = partial.CompletedState();
+void AddHypothesis(ContextBase &context, Trie &root, const NBestComplete &end) {
+  const lm::ngram::ChartState &state = *end.state;
   
   unsigned char left = 0, right = 0;
   Trie *node = &root;
@@ -81,30 +60,9 @@ void AddHypothesis(ContextBase &context, Trie &root, PartialEdge partial) {
   }
 
   node = &FindOrInsert(context, *node, kCompleteAdd - state.left.full, state, state.left.length, true, state.right.length, true);
-  CompleteTransition(context, *node, partial);
-}
-
-} // namespace
-
-#else // BOOST_VERSION
-
-struct Trie {
-  VertexNode *under;
-};
-
-void AddHypothesis(ContextBase &context, Trie &root, PartialEdge partial) {
-  UTIL_THROW(util::Exception, "Upgrade Boost to >= 1.42.0 to use incremental search.");
+  node->under->SetEnd(end.history, end.score);
 }
 
 #endif // BOOST_VERSION
 
-void VertexGenerator::FinishedSearch() {
-  Trie root;
-  root.under = &gen_.root_;
-  for (Existing::const_iterator i(existing_.begin()); i != existing_.end(); ++i) {
-    AddHypothesis(context_, root, i->second);
-  }
-  root.under->SortAndSet(context_, NULL);
-}
-
 } // namespace search
diff --git a/search/vertex_generator.hh b/search/vertex_generator.hh
index 60e86112a..da563c2df 100644
--- a/search/vertex_generator.hh
+++ b/search/vertex_generator.hh
@@ -2,9 +2,11 @@
 #define SEARCH_VERTEX_GENERATOR__
 
 #include "search/edge.hh"
+#include "search/types.hh"
 #include "search/vertex.hh"
 
 #include <boost/unordered_map.hpp>
+#include <boost/version.hpp>
 
 namespace lm {
 namespace ngram {
@@ -15,21 +17,44 @@ class ChartState;
 namespace search {
 
 class ContextBase;
-class Final;
 
-class VertexGenerator {
+#if BOOST_VERSION > 104200
+// Parallel structure to VertexNode.  
+struct Trie {
+  Trie() : under(NULL) {}
+
+  VertexNode *under;
+  boost::unordered_map<uint64_t, Trie> extend;
+};
+
+void AddHypothesis(ContextBase &context, Trie &root, const NBestComplete &end);
+
+#endif // BOOST_VERSION
+
+// Output makes the single-best or n-best list.   
+template <class Output> class VertexGenerator {
   public:
-    VertexGenerator(ContextBase &context, Vertex &gen);
+    VertexGenerator(ContextBase &context, Vertex &gen, Output &nbest) : context_(context), gen_(gen), nbest_(nbest) {
+      gen.root_.InitRoot();
+    }
 
     void NewHypothesis(PartialEdge partial) {
-      const lm::ngram::ChartState &state = partial.CompletedState();
-      std::pair<Existing::iterator, bool> ret(existing_.insert(std::make_pair(hash_value(state), partial)));
-      if (!ret.second && ret.first->second < partial) {
-        ret.first->second = partial;
-      }
+      nbest_.Add(existing_[hash_value(partial.CompletedState())], partial);
     }
 
-    void FinishedSearch();
+    void FinishedSearch() {
+#if BOOST_VERSION > 104200
+      Trie root;
+      root.under = &gen_.root_;
+      for (typename Existing::iterator i(existing_.begin()); i != existing_.end(); ++i) {
+        AddHypothesis(context_, root, nbest_.Complete(i->second));
+      }
+      existing_.clear();
+      root.under->SortAndSet(context_);
+#else
+      UTIL_THROW(util::Exception, "Upgrade Boost to >= 1.42.0 to use incremental search.");
+#endif
+    }
 
     const Vertex &Generating() const { return gen_; }
 
@@ -38,8 +63,35 @@ class VertexGenerator {
 
     Vertex &gen_;
 
-    typedef boost::unordered_map<uint64_t, PartialEdge> Existing;
+    typedef boost::unordered_map<uint64_t, typename Output::Combine> Existing;
     Existing existing_;
+
+    Output &nbest_;
+};
+
+// Special case for root vertex: everything should come together into the root
+// node.  In theory, this should happen naturally due to state collapsing with
+// <s> and </s>.  If that's the case, VertexGenerator is fine, though it will
+// make one connection.  
+template <class Output> class RootVertexGenerator {
+  public:
+    RootVertexGenerator(Vertex &gen, Output &out) : gen_(gen), out_(out) {}
+
+    void NewHypothesis(PartialEdge partial) {
+      out_.Add(combine_, partial);
+    }
+
+    void FinishedSearch() {
+      gen_.root_.InitRoot();
+      NBestComplete completed(out_.Complete(combine_));
+      gen_.root_.SetEnd(completed.history, completed.score);
+    }
+
+  private:
+    Vertex &gen_;
+    
+    typename Output::Combine combine_;
+    Output &out_;
 };
 
 } // namespace search
diff --git a/search/weights.cc b/search/weights.cc
deleted file mode 100644
index d65471ad7..000000000
--- a/search/weights.cc
+++ /dev/null
@@ -1,71 +0,0 @@
-#include "search/weights.hh"
-#include "util/tokenize_piece.hh"
-
-#include <cstdlib>
-
-namespace search {
-
-namespace {
-struct Insert {
-  void operator()(boost::unordered_map<std::string, search::Score> &map, StringPiece name, search::Score score) const {
-    std::string copy(name.data(), name.size());
-    map[copy] = score;
-  }
-};
-
-struct DotProduct {
-  search::Score total;
-  DotProduct() : total(0.0) {}
-
-  void operator()(const boost::unordered_map<std::string, search::Score> &map, StringPiece name, search::Score score) {
-    boost::unordered_map<std::string, search::Score>::const_iterator i(FindStringPiece(map, name));
-    if (i != map.end()) 
-      total += score * i->second;
-  }
-};
-
-template <class Map, class Op> void Parse(StringPiece text, Map &map, Op &op) {
-  for (util::TokenIter<util::SingleCharacter, true> spaces(text, ' '); spaces; ++spaces) {
-    util::TokenIter<util::SingleCharacter> equals(*spaces, '=');
-    UTIL_THROW_IF(!equals, WeightParseException, "Bad weight token " << *spaces);
-    StringPiece name(*equals);
-    UTIL_THROW_IF(!++equals, WeightParseException, "Bad weight token " << *spaces);
-    char *end;
-    // Assumes proper termination.  
-    double value = std::strtod(equals->data(), &end);
-    UTIL_THROW_IF(end != equals->data() + equals->size(), WeightParseException, "Failed to parse weight" << *equals);
-    UTIL_THROW_IF(++equals, WeightParseException, "Too many equals in " << *spaces);
-    op(map, name, value);
-  }
-}
-
-} // namespace
-
-Weights::Weights(StringPiece text) {
-  Insert op;
-  Parse<Map, Insert>(text, map_, op);
-  lm_ = Steal("LanguageModel");
-  oov_ = Steal("OOV");
-  word_penalty_ = Steal("WordPenalty");
-}
-
-Weights::Weights(Score lm, Score oov, Score word_penalty) : lm_(lm), oov_(oov), word_penalty_(word_penalty) {}
-
-search::Score Weights::DotNoLM(StringPiece text) const {
-  DotProduct dot;
-  Parse<const Map, DotProduct>(text, map_, dot);
-  return dot.total;
-}
-
-float Weights::Steal(const std::string &str) {
-  Map::iterator i(map_.find(str));
-  if (i == map_.end()) {
-    return 0.0;
-  } else {
-    float ret = i->second;
-    map_.erase(i);
-    return ret;
-  }
-}
-
-} // namespace search
diff --git a/search/weights.hh b/search/weights.hh
deleted file mode 100644
index df1c419f0..000000000
--- a/search/weights.hh
+++ /dev/null
@@ -1,52 +0,0 @@
-// For now, the individual features are not kept.  
-#ifndef SEARCH_WEIGHTS__
-#define SEARCH_WEIGHTS__
-
-#include "search/types.hh"
-#include "util/exception.hh"
-#include "util/string_piece.hh"
-
-#include <boost/unordered_map.hpp>
-
-#include <string>
-
-namespace search {
-
-class WeightParseException : public util::Exception {
-  public:
-    WeightParseException() {}
-    ~WeightParseException() throw() {}
-};
-
-class Weights {
-  public:
-    // Parses weights, sets lm_weight_, removes it from map_.
-    explicit Weights(StringPiece text);
-
-    // Just the three scores we care about adding.   
-    Weights(Score lm, Score oov, Score word_penalty);
-
-    Score DotNoLM(StringPiece text) const;
-
-    Score LM() const { return lm_; }
-
-    Score OOV() const { return oov_; }
-
-    Score WordPenalty() const { return word_penalty_; }
-
-    // Mostly for testing.  
-    const boost::unordered_map<std::string, Score> &GetMap() const { return map_; }
-
-  private:
-    float Steal(const std::string &str);
-
-    typedef boost::unordered_map<std::string, Score> Map;
-
-    Map map_;
-
-    Score lm_, oov_, word_penalty_;
-};
-
-} // namespace search
-
-#endif // SEARCH_WEIGHTS__
diff --git a/search/weights_test.cc b/search/weights_test.cc
deleted file mode 100644
index 4811ff060..000000000
--- a/search/weights_test.cc
+++ /dev/null
@@ -1,38 +0,0 @@
-#include "search/weights.hh"
-
-#define BOOST_TEST_MODULE WeightTest
-#include <boost/test/unit_test.hpp>
-#include <boost/test/floating_point_comparison.hpp>
-
-namespace search {
-namespace {
-
-#define CHECK_WEIGHT(value, string) \
-  i = parsed.find(string); \
-  BOOST_REQUIRE(i != parsed.end()); \
-  BOOST_CHECK_CLOSE((value), i->second, 0.001);
-
-BOOST_AUTO_TEST_CASE(parse) {
-  // These are not real feature weights.  
-  Weights w("rarity=0 phrase-SGT=0 phrase-TGS=9.45117 lhsGrhs=0 lexical-SGT=2.33833 lexical-TGS=-28.3317 abstract?=0 LanguageModel=3 lexical?=1 glue?=5");
-  const boost::unordered_map<std::string, search::Score> &parsed = w.GetMap();
-  boost::unordered_map<std::string, search::Score>::const_iterator i;
-  CHECK_WEIGHT(0.0, "rarity");
-  CHECK_WEIGHT(0.0, "phrase-SGT");
-  CHECK_WEIGHT(9.45117, "phrase-TGS");
-  CHECK_WEIGHT(2.33833, "lexical-SGT");
-  BOOST_CHECK(parsed.end() == parsed.find("lm"));
-  BOOST_CHECK_CLOSE(3.0, w.LM(), 0.001);
-  CHECK_WEIGHT(-28.3317, "lexical-TGS");
-  CHECK_WEIGHT(5.0, "glue?");
-}
-
-BOOST_AUTO_TEST_CASE(dot) {
-  Weights w("rarity=0 phrase-SGT=0 phrase-TGS=9.45117 lhsGrhs=0 lexical-SGT=2.33833 lexical-TGS=-28.3317 abstract?=0 LanguageModel=3 lexical?=1 glue?=5");
-  BOOST_CHECK_CLOSE(9.45117 * 3.0, w.DotNoLM("phrase-TGS=3.0"), 0.001);
-  BOOST_CHECK_CLOSE(9.45117 * 3.0, w.DotNoLM("phrase-TGS=3.0 LanguageModel=10"), 0.001);
-  BOOST_CHECK_CLOSE(9.45117 * 3.0 + 28.3317 * 17.4, w.DotNoLM("rarity=5 phrase-TGS=3.0 LanguageModel=10 lexical-TGS=-17.4"), 0.001);
-}
-
-} // namespace
-} // namespace search