From de53e2e98acd0e2d07efb39bef430bd598908aa8 Mon Sep 17 00:00:00 2001
From: Kenneth Heafield <github@kheafield.com>
Date: Fri, 14 Dec 2012 12:39:04 -0800
Subject: Updated incremental, updated kenlm.  Incremental assumes <s>

---
 klm/search/nbest.cc | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 klm/search/nbest.cc

(limited to 'klm/search/nbest.cc')

diff --git a/klm/search/nbest.cc b/klm/search/nbest.cc
new file mode 100644
index 00000000..ec3322c9
--- /dev/null
+++ b/klm/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
-- 
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