Function xgboost_sys::RabitCheckPoint

pub unsafe extern "C" fn RabitCheckPoint(
    global_model: *const c_char,
    global_len: rbt_ulong,
    local_model: *const c_char,
    local_len: rbt_ulong
)

\brief checkpoint the model, meaning we finished a stage of execution every time we call check point, there is a version number which will increase by one

\param global_model hold content of serialized global_model \param global_len the content length of serialized global model \param local_model hold content of serialized local_model, can be NULL \param local_len the content length of serialized local model, can be NULL

NOTE: local_model requires explicit replication of the model for fault-tolerance, which will bring replication cost in CheckPoint function. global_model do not need explicit replication. So only CheckPoint with global_model if possible