diff --git a/gtsam/inference/BayesTreeCliqueBase.h b/gtsam/inference/BayesTreeCliqueBase.h
index e81565e65..63c52ad5f 100644
--- a/gtsam/inference/BayesTreeCliqueBase.h
+++ b/gtsam/inference/BayesTreeCliqueBase.h
@@ -66,10 +66,10 @@ namespace gtsam {
     /// @{
 
     /** Default constructor */
-    BayesTreeCliqueBase() {}
+    BayesTreeCliqueBase() : problemSize_(1) {}
 
     /** Construct from a conditional, leaving parent and child pointers uninitialized */
-    BayesTreeCliqueBase(const sharedConditional& conditional) : conditional_(conditional) {}
+    BayesTreeCliqueBase(const sharedConditional& conditional) : conditional_(conditional), problemSize_(1) {}
 
     /// @}
 
@@ -80,6 +80,7 @@ namespace gtsam {
     sharedConditional conditional_;
     derived_weak_ptr parent_;
     FastVector<derived_ptr> children;
+    int problemSize_;
 
     /// Fill the elimination result produced during elimination.  Here this just stores the
     /// conditional and ignores the remaining factor, but this is overridden in ISAM2Clique
@@ -114,6 +115,9 @@ namespace gtsam {
     /** return a shared_ptr to the parent clique */
     derived_ptr parent() const { return parent_.lock(); }
 
+    /** Problem size (used for parallel traversal) */
+    int problemSize() const { return problemSize_; }
+
     /// @}
     /// @name Advanced Interface
     /// @{
diff --git a/gtsam/inference/JunctionTree-inst.h b/gtsam/inference/JunctionTree-inst.h
index 401ba174e..298bf6389 100644
--- a/gtsam/inference/JunctionTree-inst.h
+++ b/gtsam/inference/JunctionTree-inst.h
@@ -156,7 +156,9 @@ namespace gtsam {
     EliminationData<JUNCTIONTREE> eliminationPreOrderVisitor(
       const typename JUNCTIONTREE::sharedNode& node, EliminationData<JUNCTIONTREE>& parentData)
     {
-      return EliminationData<JUNCTIONTREE>(&parentData, node->children.size());
+      EliminationData<JUNCTIONTREE> myData(&parentData, node->children.size());
+      myData.bayesTreeNode->problemSize_ = node->problemSize();
+      return myData;
     }
 
     /* ************************************************************************* */
diff --git a/gtsam/linear/VectorValues.cpp b/gtsam/linear/VectorValues.cpp
index 77e63ba7b..11967e858 100644
--- a/gtsam/linear/VectorValues.cpp
+++ b/gtsam/linear/VectorValues.cpp
@@ -63,7 +63,7 @@ namespace gtsam {
       size_t oldSize = values_.size();
       hint = values_.insert(hint, key_value);
       if(values_.size() > oldSize) {
-        values_.erase(hint);
+        values_.unsafe_erase(hint);
         throw std::out_of_range("Requested to update a VectorValues with another VectorValues that contains keys not present in the first.");
       } else {
         hint->second = key_value.second;
diff --git a/gtsam/linear/VectorValues.h b/gtsam/linear/VectorValues.h
index 125cc8060..65c385d11 100644
--- a/gtsam/linear/VectorValues.h
+++ b/gtsam/linear/VectorValues.h
@@ -24,6 +24,11 @@
 
 #include <boost/shared_ptr.hpp>
 
+#include <tbb/concurrent_unordered_map.h>
+#undef min
+#undef max
+#undef ERROR
+
 namespace gtsam {
 
   /**
@@ -88,14 +93,14 @@ namespace gtsam {
   class GTSAM_EXPORT VectorValues {
   protected:
     typedef VectorValues This;
-    typedef FastMap<Key, Vector> Values; ///< Typedef for the collection of Vectors making up a VectorValues
+    typedef tbb::concurrent_unordered_map<Key, Vector> Values; ///< Typedef for the collection of Vectors making up a VectorValues
     Values values_; ///< Collection of Vectors making up this VectorValues
 
   public:
     typedef Values::iterator iterator; ///< Iterator over vector values
     typedef Values::const_iterator const_iterator; ///< Const iterator over vector values
-    typedef Values::reverse_iterator reverse_iterator; ///< Reverse iterator over vector values
-    typedef Values::const_reverse_iterator const_reverse_iterator; ///< Const reverse iterator over vector values
+    //typedef Values::reverse_iterator reverse_iterator; ///< Reverse iterator over vector values
+    //typedef Values::const_reverse_iterator const_reverse_iterator; ///< Const reverse iterator over vector values
     typedef boost::shared_ptr<This> shared_ptr; ///< shared_ptr to this class
     typedef Values::value_type value_type; ///< Typedef to pair<Key, Vector>, a key-value pair
     typedef value_type KeyValuePair; ///< Typedef to pair<Key, Vector>, a key-value pair
@@ -207,7 +212,7 @@ namespace gtsam {
 
     /** Erase the vector with the given key, or throw std::out_of_range if it does not exist */
     void erase(Key var) {
-      if(values_.erase(var) == 0)
+      if(values_.unsafe_erase(var) == 0)
         throw std::invalid_argument("Requested variable '" + DefaultKeyFormatter(var) + "', is not in this VectorValues.");
     }
 
@@ -218,10 +223,10 @@ namespace gtsam {
     const_iterator begin() const          { return values_.begin(); }  ///< Iterator over variables
     iterator end()                        { return values_.end(); }    ///< Iterator over variables
     const_iterator end() const            { return values_.end(); }    ///< Iterator over variables
-    reverse_iterator rbegin()             { return values_.rbegin(); } ///< Reverse iterator over variables
-    const_reverse_iterator rbegin() const { return values_.rbegin(); } ///< Reverse iterator over variables
-    reverse_iterator rend()               { return values_.rend(); }   ///< Reverse iterator over variables
-    const_reverse_iterator rend() const   { return values_.rend(); }   ///< Reverse iterator over variables
+    //reverse_iterator rbegin()             { return values_.rbegin(); } ///< Reverse iterator over variables
+    //const_reverse_iterator rbegin() const { return values_.rbegin(); } ///< Reverse iterator over variables
+    //reverse_iterator rend()               { return values_.rend(); }   ///< Reverse iterator over variables
+    //const_reverse_iterator rend() const   { return values_.rend(); }   ///< Reverse iterator over variables
 
     /** Return the iterator corresponding to the requested key, or end() if no variable is present with this key. */
     iterator find(Key j) { return values_.find(j); }
diff --git a/gtsam/linear/linearAlgorithms-inst.h b/gtsam/linear/linearAlgorithms-inst.h
index 29e1e1096..4ec8c9a07 100644
--- a/gtsam/linear/linearAlgorithms-inst.h
+++ b/gtsam/linear/linearAlgorithms-inst.h
@@ -132,7 +132,8 @@ namespace gtsam
         //return rootData.results;
         OptimizeData rootData;
         OptimizeClique<typename BAYESTREE::Clique> preVisitor;
-        treeTraversal::DepthFirstForest(bayesTree, rootData, preVisitor);
+        treeTraversal::no_op postVisitor;
+        treeTraversal::DepthFirstForestParallel(bayesTree, rootData, preVisitor, postVisitor);
         return preVisitor.collectedResult;
       }
     }