MPI_Bsend(3) MPI MPI_Bsend(3) NAME MPI_Bsend - Basic send with user-provided buffering SYNOPSIS int MPI_Bsend(const void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm) int MPI_Bsend_c(const void *buf, MPI_Count count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm) INPUT PARAMETERS buf - initial address of send buffer (choice) count - number of elements in send buffer (non-negative integer) datatype - datatype of each send buffer element (handle) dest - rank of destination (integer) tag - message tag (integer) comm - communicator (handle) NOTES This send is provided as a convenience function; it allows the user to send messages without worring about where they are buffered (because the user must have provided buffer space with MPI_Buffer_attach ). In deciding how much buffer space to allocate, remember that the buffer space is not available for reuse by subsequent MPI_Bsend s unless you are certain that the message has been received (not just that it should have been received). For example, this code does not allocate enough buffer space MPI_Buffer_attach(b, n*sizeof(double) + MPI_BSEND_OVERHEAD); for (i=0; i<m; i++) { MPI_Bsend(buf, n, MPI_DOUBLE, ...); } because only enough buffer space is provided for a single send, and the loop may start a second MPI_Bsend before the first is done making use of the buffer. In C, you can force the messages to be delivered by MPI_Buffer_detach(&b, &n); MPI_Buffer_attach(b, n); (The MPI_Buffer_detach will not complete until all buffered messages are delivered.) THREAD AND INTERRUPT SAFETY This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. NOTES FOR FORTRAN All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the end of the argument list. ierr is an inte- ger and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call state- ment. All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran. ERRORS All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the function and Fortran routines in the last ar- gument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error han- dler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible. MPI_SUCCESS - No error; MPI routine completed successfully. MPI_ERR_BUFFER - Invalid buffer pointer. Usually a null buffer where one is not valid. MPI_ERR_COMM - Invalid communicator. A common error is to use a null communica- tor in a call (not even allowed in MPI_Comm_rank ). MPI_ERR_COUNT - Invalid count argument. Count arguments must be non-negative; a count of zero is often valid. MPI_ERR_RANK - Invalid source or destination rank. Ranks must be between zero and the size of the communicator minus one; ranks in a receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also be MPI_ANY_SOURCE . MPI_ERR_TAG - Invalid tag argument. Tags must be non-negative; tags in a re- ceive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also be MPI_ANY_TAG . The largest tag value is available through the the attribute MPI_TAG_UB . MPI_ERR_TYPE - Invalid datatype argument. Additionally, this error can occur if an uncommitted MPI_Datatype (see MPI_Type_commit ) is used in a com- munication call. MPI_ERR_OTHER - Other error; use MPI_Error_string to get more information about this error code. SEE ALSO MPI_Buffer_attach, MPI_Ibsend, MPI_Bsend_init 4/10/2026 MPI_Bsend(3)
NAME | SYNOPSIS | INPUT PARAMETERS | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | SEE ALSO
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