diff --git a/src/tree/updater_basemaker-inl.hpp b/src/tree/updater_basemaker-inl.hpp
new file mode 100644
index 000000000..17469658f
--- /dev/null
+++ b/src/tree/updater_basemaker-inl.hpp
@@ -0,0 +1,148 @@
+#ifndef XGBOOST_TREE_UPDATER_BASEMAKER_INL_HPP_
+#define XGBOOST_TREE_UPDATER_BASEMAKER_INL_HPP_
+/*!
+ * \file updater_basemaker-inl.hpp
+ * \brief implement a common tree constructor
+ * \author Tianqi Chen
+ */
+#include <vector>
+#include <algorithm>
+#include "../utils/random.h"
+
+namespace xgboost {
+namespace tree {
+/*! 
+ * \brief base tree maker class that defines common operation
+ *  needed in tree making
+ */
+class BaseMaker: public IUpdater {
+ public:
+  // destructor
+  virtual ~BaseMaker(void) {}
+  // set training parameter
+  virtual void SetParam(const char *name, const char *val) {
+    param.SetParam(name, val);
+  }
+  
+ protected:
+  // ------static helper functions ------
+  // helper function to get to next level of the tree
+  // must work on non-leaf node
+  inline static int NextLevel(const SparseBatch::Inst &inst, const RegTree &tree, int nid) {
+    const RegTree::Node &n = tree[nid];
+    bst_uint findex = n.split_index();
+    for (unsigned i = 0; i < inst.length; ++i) {
+      if (findex == inst[i].index) {
+        if (inst[i].fvalue < n.split_cond()) {
+          return n.cleft();
+        } else {
+          return n.cright();
+        }
+      }
+    }
+    return n.cdefault();
+  }
+  /*! \brief get number of omp thread in current context */
+  inline static int get_nthread(void) {
+    int nthread;
+    #pragma omp parallel
+    {
+      nthread = omp_get_num_threads();
+    }
+    return nthread;
+  }
+  // ------class member helpers---------
+  // return decoded position
+  inline int DecodePosition(bst_uint ridx) const{
+    const int pid = position[ridx];
+    return pid < 0 ? ~pid : pid;
+  }
+  // encode the encoded position value for ridx
+  inline void SetEncodePosition(bst_uint ridx, int nid) {
+    if (position[ridx] < 0) {
+      position[ridx] = ~nid;
+    } else {
+      position[ridx] = nid;
+    }
+  }
+  /*! \brief initialize temp data structure */
+  inline void InitData(const std::vector<bst_gpair> &gpair,
+                       const IFMatrix &fmat,
+                       const std::vector<unsigned> &root_index,
+                       const RegTree &tree) {
+    utils::Assert(tree.param.num_nodes == tree.param.num_roots,
+                  "TreeMaker: can only grow new tree");
+    {// setup position
+      position.resize(gpair.size());
+      if (root_index.size() == 0) {
+        std::fill(position.begin(), position.end(), 0);
+      } else {
+        for (size_t i = 0; i < position.size(); ++i) {
+          position[i] = root_index[i];
+          utils::Assert(root_index[i] < (unsigned)tree.param.num_roots,
+                        "root index exceed setting");
+        }
+      }
+      // mark delete for the deleted datas
+      for (size_t i = 0; i < position.size(); ++i) {
+        if (gpair[i].hess < 0.0f) position[i] = ~position[i];
+      }
+      // mark subsample
+      if (param.subsample < 1.0f) {
+        for (size_t i = 0; i < position.size(); ++i) {
+          if (gpair[i].hess < 0.0f) continue;
+          if (random::SampleBinary(param.subsample) == 0) position[i] = ~position[i];
+        }
+      }
+    }
+    {// expand query
+      qexpand.reserve(256); qexpand.clear();
+      for (int i = 0; i < tree.param.num_roots; ++i) {
+        qexpand.push_back(i);
+      }
+      this->UpdateNode2WorkIndex(tree);
+    }
+  }
+  /*! \brief update queue expand add in new leaves */
+  inline void UpdateQueueExpand(const RegTree &tree) {
+    std::vector<int> newnodes;
+    for (size_t i = 0; i < qexpand.size(); ++i) {
+      const int nid = qexpand[i];
+      if (!tree[nid].is_leaf()) {
+        newnodes.push_back(tree[nid].cleft());
+        newnodes.push_back(tree[nid].cright());
+      }
+    }
+    // use new nodes for qexpand
+    qexpand = newnodes;
+    this->UpdateNode2WorkIndex(tree);
+  }
+  /*! \brief training parameter of tree grower */
+  TrainParam param;
+  /*! \brief queue of nodes to be expanded */
+  std::vector<int> qexpand;
+  /*!
+   * \brief map active node to is working index offset in qexpand,
+   *   can be -1, which means the node is node actively expanding
+   */
+  std::vector<int> node2workindex;
+  /*!
+   * \brief position of each instance in the tree
+   *   can be negative, which means this position is no longer expanding
+   *   see also Decode/EncodePosition
+   */
+  std::vector<int> position;
+
+ private:
+  inline void UpdateNode2WorkIndex(const RegTree &tree) {
+    // update the node2workindex
+    std::fill(node2workindex.begin(), node2workindex.end(), -1);
+    node2workindex.resize(tree.param.num_nodes);
+    for (size_t i = 0; i < qexpand.size(); ++i) {
+      node2workindex[qexpand[i]] = static_cast<int>(i);
+    }
+  }
+};
+}  // namespace tree
+}  // namespace xgboost
+#endif // XGBOOST_TREE_UPDATER_BASEMAKER_INL_HPP_
diff --git a/src/tree/updater_histmaker-inl.hpp b/src/tree/updater_histmaker-inl.hpp
index 7036010e7..608008515 100644
--- a/src/tree/updater_histmaker-inl.hpp
+++ b/src/tree/updater_histmaker-inl.hpp
@@ -10,17 +10,14 @@
 #include "../sync/sync.h"
 #include "../utils/quantile.h"
 #include "../utils/group_data.h"
+#include "./updater_basemaker-inl.hpp"
 
 namespace xgboost {
 namespace tree {
 template<typename TStats>
-class HistMaker: public IUpdater {
+class HistMaker: public BaseMaker {
  public:
   virtual ~HistMaker(void) {}
-  // set training parameter
-  virtual void SetParam(const char *name, const char *val) {
-    param.SetParam(name, val);
-  }
   virtual void Update(const std::vector<bst_gpair> &gpair,
                       IFMatrix *p_fmat,
                       const BoosterInfo &info,
@@ -113,34 +110,11 @@ class HistMaker: public IUpdater {
       return rptr.size() - 1;
     }
   };  
-  // training parameter
-  TrainParam param;
   // workspace of thread
   ThreadWSpace wspace;
-  // position of each data
-  std::vector<int> position;
-  /*! \brief queue of nodes to be expanded */
-  std::vector<int> qexpand;
-  /*! \brief map active node to is working index offset in qexpand*/
-  std::vector<int> node2workindex;
   // reducer for histogram
   sync::Reducer<TStats> histred;  
-  // helper function to get to next level of the tree
-  // must work on non-leaf node
-  inline static int NextLevel(const SparseBatch::Inst &inst, const RegTree &tree, int nid) {
-    const RegTree::Node &n = tree[nid];
-    bst_uint findex = n.split_index();
-    for (unsigned i = 0; i < inst.length; ++i) {
-      if (findex == inst[i].index) {
-        if (inst[i].fvalue < n.split_cond()) {
-          return n.cleft();
-        } else {
-          return n.cright();
-        }
-      }
-    }
-    return n.cdefault();
-  }
+
   // this function does two jobs
   // (1) reset the position in array position, to be the latest leaf id
   // (2) propose a set of candidate cuts and set wspace.rptr wspace.cut correctly 
@@ -154,11 +128,9 @@ class HistMaker: public IUpdater {
                       const BoosterInfo &info,
                       RegTree *p_tree) {
     this->InitData(gpair, *p_fmat, info.root_index, *p_tree);
-    this->UpdateNode2WorkIndex(*p_tree);
     for (int depth = 0; depth < param.max_depth; ++depth) {
       this->FindSplit(depth, gpair, p_fmat, info, p_tree);
       this->UpdateQueueExpand(*p_tree);
-      this->UpdateNode2WorkIndex(*p_tree);
       // if nothing left to be expand, break
       if (qexpand.size() == 0) break;
     }
@@ -167,64 +139,6 @@ class HistMaker: public IUpdater {
       (*p_tree)[nid].set_leaf(p_tree->stat(nid).base_weight * param.learning_rate);
     }
   }
-  // initialize temp data structure
-  inline void InitData(const std::vector<bst_gpair> &gpair,
-                       const IFMatrix &fmat,
-                       const std::vector<unsigned> &root_index,
-                       const RegTree &tree) {
-    utils::Assert(tree.param.num_nodes == tree.param.num_roots,
-                  "HistMaker: can only grow new tree");
-    {// setup position
-      position.resize(gpair.size());
-      if (root_index.size() == 0) {
-        std::fill(position.begin(), position.end(), 0);
-      } else {
-        for (size_t i = 0; i < position.size(); ++i) {
-          position[i] = root_index[i];
-          utils::Assert(root_index[i] < (unsigned)tree.param.num_roots,
-                        "root index exceed setting");
-        }
-      }
-      // mark delete for the deleted datas
-      for (size_t i = 0; i < position.size(); ++i) {
-        if (gpair[i].hess < 0.0f) position[i] = ~position[i];
-      }
-      // mark subsample
-      if (param.subsample < 1.0f) {
-        for (size_t i = 0; i < position.size(); ++i) {
-          if (gpair[i].hess < 0.0f) continue;
-          if (random::SampleBinary(param.subsample) == 0) position[i] = ~position[i];
-        }
-      }
-    }
-    {// expand query
-      qexpand.reserve(256); qexpand.clear();
-      for (int i = 0; i < tree.param.num_roots; ++i) {
-        qexpand.push_back(i);
-      }
-    }
-  }
-  /*! \brief update queue expand add in new leaves */
-  inline void UpdateQueueExpand(const RegTree &tree) {
-    std::vector<int> newnodes;
-    for (size_t i = 0; i < qexpand.size(); ++i) {
-      const int nid = qexpand[i];
-      if (!tree[nid].is_leaf()) {
-        newnodes.push_back(tree[nid].cleft());
-        newnodes.push_back(tree[nid].cright());
-      }
-    }
-    // use new nodes for qexpand
-    qexpand = newnodes;
-  }
-  inline void UpdateNode2WorkIndex(const RegTree &tree) {
-    // update the node2workindex
-    std::fill(node2workindex.begin(), node2workindex.end(), -1);
-    node2workindex.resize(tree.param.num_nodes);
-    for (size_t i = 0; i < qexpand.size(); ++i) {
-      node2workindex[qexpand[i]] = static_cast<int>(i);
-    }
-  }
   inline void CreateHist(const std::vector<bst_gpair> &gpair,
                          IFMatrix *p_fmat,
                          const BoosterInfo &info,