complete refactor data.h, now replies on iterator to access column

src/io/io.h

@@ -13,7 +13,7 @@ namespace xgboost {
 /*! \brief namespace related to data format */
 namespace io {
 /*! \brief DMatrix object that I/O module support save/load */
-typedef learner::DMatrix<FMatrixS> DataMatrix;
+typedef learner::DMatrix DataMatrix;
 /*!
  * \brief load DataMatrix from stream
  * \param fname file name to be loaded

src/io/simple_dmatrix-inl.hpp

@@ -229,7 +229,7 @@ class DMatrixSimple : public DataMatrix {
       at_first_ = false;
       batch_.size = parent_->row_ptr_.size() - 1;
       batch_.base_rowid = 0;
-      batch_.row_ptr = &parent_->row_ptr_[0];
+      batch_.ind_ptr = &parent_->row_ptr_[0];
       batch_.data_ptr = &parent_->row_data_[0];
       return true;
     }