Add Model and Configurable interface. (#4945)

* Apply Configurable to objective functions.
* Apply Model to Learner and Regtree, gbm.
* Add Load/SaveConfig to objs.
* Refactor obj tests to use smart pointer.
* Dummy methods for Save/Load Model.

src/tree/tree_model.cc

@@ -617,6 +617,35 @@ std::string RegTree::DumpModel(const FeatureMap& fmap,
   return result;
 }
 
+void RegTree::LoadModel(dmlc::Stream* fi) {
+  CHECK_EQ(fi->Read(&param, sizeof(TreeParam)), sizeof(TreeParam));
+  nodes_.resize(param.num_nodes);
+  stats_.resize(param.num_nodes);
+  CHECK_NE(param.num_nodes, 0);
+  CHECK_EQ(fi->Read(dmlc::BeginPtr(nodes_), sizeof(Node) * nodes_.size()),
+           sizeof(Node) * nodes_.size());
+  CHECK_EQ(fi->Read(dmlc::BeginPtr(stats_), sizeof(RTreeNodeStat) * stats_.size()),
+           sizeof(RTreeNodeStat) * stats_.size());
+  // chg deleted nodes
+  deleted_nodes_.resize(0);
+  for (int i = param.num_roots; i < param.num_nodes; ++i) {
+    if (nodes_[i].IsDeleted()) deleted_nodes_.push_back(i);
+  }
+  CHECK_EQ(static_cast<int>(deleted_nodes_.size()), param.num_deleted);
+}
+/*!
+   * \brief save model to stream
+   * \param fo output stream
+   */
+void RegTree::SaveModel(dmlc::Stream* fo) const {
+  CHECK_EQ(param.num_nodes, static_cast<int>(nodes_.size()));
+  CHECK_EQ(param.num_nodes, static_cast<int>(stats_.size()));
+  fo->Write(&param, sizeof(TreeParam));
+  CHECK_NE(param.num_nodes, 0);
+  fo->Write(dmlc::BeginPtr(nodes_), sizeof(Node) * nodes_.size());
+  fo->Write(dmlc::BeginPtr(stats_), sizeof(RTreeNodeStat) * nodes_.size());
+}
+
 void RegTree::FillNodeMeanValues() {
   size_t num_nodes = this->param.num_nodes;
   if (this->node_mean_values_.size() == num_nodes) {

src/tree/updater_gpu_hist.cu

@@ -1053,12 +1053,12 @@ class GPUHistMakerSpecialised {
     common::MemoryBufferStream fs(&s_model);
     int rank = rabit::GetRank();
     if (rank == 0) {
-      local_trees.front().Save(&fs);
+      local_trees.front().SaveModel(&fs);
     }
     fs.Seek(0);
     rabit::Broadcast(&s_model, 0);
     RegTree reference_tree{};
-    reference_tree.Load(&fs);
+    reference_tree.LoadModel(&fs);
     for (const auto& tree : local_trees) {
       CHECK(tree == reference_tree);
     }

src/tree/updater_sync.cc

@@ -35,13 +35,13 @@ class TreeSyncher: public TreeUpdater {
     int rank = rabit::GetRank();
     if (rank == 0) {
       for (auto tree : trees) {
-        tree->Save(&fs);
+        tree->SaveModel(&fs);
       }
     }
     fs.Seek(0);
     rabit::Broadcast(&s_model, 0);
     for (auto tree : trees) {
-      tree->Load(&fs);
+      tree->LoadModel(&fs);
     }
   }
 };