Hello wg-persistence, Looking at the MPI 4.0 document, it is not clear to us, whether it is allowed to call a completion call for a partitioned communication request before all partitions are marked ready. A simple single-threaded example would be: ```C MPI_Psend_init(message, partitions, COUNT, MPI_DOUBLE, dest, tag, MPI_COMM_WORLD, MPI_INFO_NULL, &request); MPI_Start(&request); for(i = 0; i < partitions-1; ++i) { MPI_Pready(i, request); } MPI_Test(&request, &flag, MPI_STATUS_IGNORE); // flag will always be 0 MPI_Pready(partitions-1, request); MPI_Wait(&request, MPI_STATUS_IGNORE); MPI_Request_free(&request); ``` The question becomes more relevant in a multi-threaded context. One thread could finish the work early and call MPI_Wait to detect when all partitions were sent. From my understanding, the only requirement is that all partitions must be marked ready with explicit ready calls before the operation can complete. Replacing the test in above example with a wait call would result in deadlock. Best Joachim -- Dr. rer. nat. Joachim Protze IT Center Group: High Performance Computing Division: Computational Science and Engineering RWTH Aachen University Seffenter Weg 23 D 52074 Aachen (Germany) Tel: +49 241 80- 24765 Fax: +49 241 80-624765 [email protected] www.itc.rwth-aachen.de