void* base() const;
int disp_unit() const;
int fence(int assert);
+ int opened() const {return opened_;}
int put(const void *origin_addr, int origin_count, MPI_Datatype origin_datatype, int target_rank,
MPI_Aint target_disp, int target_count, MPI_Datatype target_datatype, MPI_Request* request=nullptr);
int get( void *origin_addr, int origin_count, MPI_Datatype origin_datatype, int target_rank,