constexpr unsigned MPI_REQ_NON_PERSISTENT = 0x2;
constexpr unsigned MPI_REQ_SEND = 0x4;
constexpr unsigned MPI_REQ_RECV = 0x8;
-// constexpr unsigned MPI_REQ_RECV_DELETE = 0x10;
+constexpr unsigned MPI_REQ_RECV_DELETE = 0x10;
constexpr unsigned MPI_REQ_ISEND = 0x20;
constexpr unsigned MPI_REQ_SSEND = 0x40;
constexpr unsigned MPI_REQ_PREPARED = 0x80;