[TREE] Enable updater registry

src/tree/updater_sync.cc

@@ -0,0 +1,50 @@
+/*!
+ * Copyright 2014 by Contributors
+ * \file updater_sync.cc
+ * \brief synchronize the tree in all distributed nodes
+ */
+#include <xgboost/tree_updater.h>
+#include <vector>
+#include <string>
+#include <limits>
+#include "../common/sync.h"
+#include "../common/io.h"
+
+namespace xgboost {
+namespace tree {
+/*!
+ * \brief syncher that synchronize the tree in all distributed nodes
+ * can implement various strategies, so far it is always set to node 0's tree
+ */
+class TreeSyncher: public TreeUpdater {
+ public:
+  void Init(const std::vector<std::pair<std::string, std::string> >& args) override {}
+
+  void Update(const std::vector<bst_gpair> &gpair,
+              DMatrix* dmat,
+              const std::vector<RegTree*> &trees) override {
+    if (rabit::GetWorldSize() == 1) return;
+    std::string s_model;
+    common::MemoryBufferStream fs(&s_model);
+    int rank = rabit::GetRank();
+    if (rank == 0) {
+      for (size_t i = 0; i < trees.size(); ++i) {
+        trees[i]->SaveModel(&fs);
+      }
+    }
+    fs.Seek(0);
+    rabit::Broadcast(&s_model, 0);
+    for (size_t i = 0; i < trees.size(); ++i) {
+      trees[i]->LoadModel(&fs);
+    }
+  }
+};
+
+XGBOOST_REGISTER_TREE_UPDATER(TreeSyncher, "sync")
+.describe("Syncher that synchronize the tree in all distributed nodes.")
+.set_body([]() {
+    return new TreeSyncher();
+  });
+}  // namespace tree
+}  // namespace xgboost
+