Model IO in JSON. (#5110)

include/xgboost/c_api.h

@@ -428,7 +428,7 @@ XGB_DLL int XGBoosterPredict(BoosterHandle handle,
                              const float **out_result);
 
 /*!
- * \brief load model from existing file
+ * \brief Load model from existing file
  * \param handle handle
  * \param fname file name
 * \return 0 when success, -1 when failure happens
@@ -436,7 +436,7 @@ XGB_DLL int XGBoosterPredict(BoosterHandle handle,
 XGB_DLL int XGBoosterLoadModel(BoosterHandle handle,
                                const char *fname);
 /*!
- * \brief save model into existing file
+ * \brief Save model into existing file
  * \param handle handle
  * \param fname file name
  * \return 0 when success, -1 when failure happens

include/xgboost/gbm.h

@@ -32,7 +32,7 @@ struct LearnerModelParam;
 /*!
  * \brief interface of gradient boosting model.
  */
-class GradientBooster {
+class GradientBooster : public Model {
  protected:
   GenericParameter const* generic_param_;
 

include/xgboost/json_io.h

@@ -21,7 +21,7 @@ class FixedPrecisionStreamContainer : public std::basic_stringstream<
   char, std::char_traits<char>, Allocator> {
  public:
   FixedPrecisionStreamContainer() {
-    this->precision(std::numeric_limits<Number::Float>::max_digits10);
+    this->precision(std::numeric_limits<double>::max_digits10);
     this->imbue(std::locale("C"));
     this->setf(std::ios::scientific);
   }

include/xgboost/model.h

@@ -16,15 +16,15 @@ class Json;
 
 struct Model {
   /*!
-   * \brief Save the model to stream.
-   * \param fo output write stream
+   * \brief load the model from a json object
+   * \param in json object where to load the model from
    */
-  virtual void SaveModel(dmlc::Stream* fo) const = 0;
+  virtual void LoadModel(Json const& in) = 0;
   /*!
-   * \brief Load the model from stream.
-   * \param fi input read stream
+   * \brief saves the model config to a json object
+   * \param out json container where to save the model to
    */
-  virtual void LoadModel(dmlc::Stream* fi) = 0;
+  virtual void SaveModel(Json* out) const = 0;
 };
 
 struct Configurable {

include/xgboost/tree_model.h

@@ -303,12 +303,15 @@ class RegTree : public Model {
    * \brief load model from stream
    * \param fi input stream
    */
-  void LoadModel(dmlc::Stream* fi) override;
+  void Load(dmlc::Stream* fi);
   /*!
    * \brief save model to stream
    * \param fo output stream
    */
-  void SaveModel(dmlc::Stream* fo) const override;
+  void Save(dmlc::Stream* fo) const;
+
+  void LoadModel(Json const& in) override;
+  void SaveModel(Json* out) const override;
 
   bool operator==(const RegTree& b) const {
     return nodes_ == b.nodes_ && stats_ == b.stats_ &&