[TREE] Enable updater registry

include/xgboost/sync.h

@@ -1,13 +0,0 @@
-/*!
- * Copyright 2014 by Contributors
- * \file sync.h
- * \brief the synchronization module of rabit
- *        redirects to rabit header
- * \author Tianqi Chen
- */
-#ifndef XGBOOST_SYNC_H_
-#define XGBOOST_SYNC_H_
-
-#include <rabit.h>
-
-#endif  // XGBOOST_SYNC_H_

include/xgboost/tree_model.h

@@ -332,8 +332,8 @@ class TreeModel {
     CHECK_EQ(param.num_nodes, static_cast<int>(stats.size()));
     fo->Write(&param, sizeof(TreeParam));
     CHECK_NE(param.num_nodes, 0);
-    fo->Write(BeginPtr(nodes), sizeof(Node) * nodes.size());
-    fo->Write(BeginPtr(stats), sizeof(NodeStat) * nodes.size());
+    fo->Write(dmlc::BeginPtr(nodes), sizeof(Node) * nodes.size());
+    fo->Write(dmlc::BeginPtr(stats), sizeof(NodeStat) * nodes.size());
     if (param.size_leaf_vector != 0) fo->Write(leaf_vector);
   }
   /*!

include/xgboost/tree_updater.h

@@ -0,0 +1,83 @@
+/*!
+ * Copyright 2014 by Contributors
+ * \file tree_updater.h
+ * \brief General primitive for tree learning,
+ *   Updating a collection of trees given the information.
+ * \author Tianqi Chen
+ */
+#ifndef XGBOOST_TREE_UPDATER_H_
+#define XGBOOST_TREE_UPDATER_H_
+
+#include <dmlc/registry.h>
+#include <vector>
+#include <utility>
+#include "./base.h"
+#include "./data.h"
+#include "./tree_model.h"
+
+namespace xgboost {
+/*!
+ * \brief interface of tree update module, that performs update of a tree.
+ */
+class TreeUpdater {
+ public:
+  /*! \brief virtual destructor */
+  virtual ~TreeUpdater() {}
+  /*!
+   * \brief Initialize the updater with given arguments.
+   * \param args arguments to the objective function.
+   */
+  virtual void Init(const std::vector<std::pair<std::string, std::string> >& args) = 0;
+  /*!
+   * \brief perform update to the tree models
+   * \param gpair the gradient pair statistics of the data
+   * \param dmat The data matrix passed to the updater.
+   * \param trees references the trees to be updated, updater will change the content of trees
+   *   note: all the trees in the vector are updated, with the same statistics,
+   *         but maybe different random seeds, usually one tree is passed in at a time,
+   *         there can be multiple trees when we train random forest style model
+   */
+  virtual void Update(const std::vector<bst_gpair>& gpair,
+                      DMatrix* data,
+                      const std::vector<RegTree*>& trees) = 0;
+  /*!
+   * \brief this is simply a function for optimizing performance
+   * this function asks the updater to return the leaf position of each instance in the previous performed update.
+   * if it is cached in the updater, if it is not available, return nullptr
+   * \return array of leaf position of each instance in the last updated tree
+   */
+  virtual const int* GetLeafPosition() const {
+    return nullptr;
+  }
+  /*!
+   * \brief Create a tree updater given name
+   * \param name Name of the tree updater.
+   */
+  static TreeUpdater* Create(const char* name);
+};
+
+/*!
+ * \brief Registry entry for tree updater.
+ */
+struct TreeUpdaterReg
+    : public dmlc::FunctionRegEntryBase<TreeUpdaterReg,
+                                        std::function<TreeUpdater* ()> > {
+};
+
+/*!
+ * \brief Macro to register tree updater.
+ *
+ * \code
+ * // example of registering a objective ndcg@k
+ * XGBOOST_REGISTER_METRIC(ColMaker, "colmaker")
+ * .describe("Column based tree maker.")
+ * .set_body([]() {
+ *     return new ColMaker<TStats>();
+ *   });
+ * \endcode
+ */
+#define XGBOOST_REGISTER_TREE_UPDATER(UniqueId, Name)                   \
+  static ::xgboost::TreeUpdaterReg & __make_ ## TreeUpdaterReg ## _ ## UniqueId ## __ = \
+      ::dmlc::Registry< ::xgboost::TreeUpdaterReg>::Get()->__REGISTER__(#Name)
+}  // namespace xgboost
+#endif  // XGBOOST_TREE_UPDATER_H_