This is a proposal for MPI 2.1, Ballot 4. This is a follow up to: Datatypes and MPI_PROBE in http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/index.h... with mail discussion in http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/discuss... Proposal for MPI 2.1, Ballot 4: ------------------------------- MPI 1.1, page 222, line 48 reads used after a call to MPI_PROBE. (End of rationale.) but should read used after a call to MPI_PROBE or MPI_IPROBE. With a status returned from MPI_PROBE or MPI_IPROBE, the same dataypes are allowed as in a call to MPI_RECV to receive this message. (End of rationale.) Advice to users. To allocate the appropriate amount of memory as receive buffer, the same datatype as in the following receive call should be used to determine the needed space. In portable programs due to possible data conversions, it is not guaranteed that the count returned by MPI_GET_COUNT with datatype MPI_BYTE is the correct amount of needed memory space in the receive buffer (although MPI_BYTE is matching every datatype). (End of advice to users.) ------------------------------- Reason for the first part: The current MPI-1.1 text says "The datatype argument should match the argument provided by the receive call that set the status variable." With MPI_PROBE, there isn't such a receive call. Reason for the advice to users: It helps to write portable code. Because malloc needs a byte count, users may write wrong programs by using MPI_BYTE. ------------------------------- Discussion should be done through the new mailing list mpi-21_at_cs.uiuc.edu. I have sent out this mail with CC through the old general list mpi-21_at_[hidden] Best regards Rolf Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner_at_[hidden] High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)