Function xgboost_sys::XGDMatrixNumRow

pub unsafe extern "C" fn XGDMatrixNumRow(
    handle: DMatrixHandle,
    out: *mut bst_ulong
) -> c_int

\brief get number of rows. \param handle the handle to the DMatrix \param out The address to hold number of rows. \return 0 when success, -1 when failure happens