MPI_Pack(3) MPI MPI_Pack(3) NAME MPI_Pack - Packs a datatype into contiguous memory SYNOPSIS int MPI_Pack(const void *inbuf, int incount, MPI_Datatype datatype, void *outbuf, int outsize, int *position, MPI_Comm comm) int MPI_Pack_c(const void *inbuf, MPI_Count incount, MPI_Datatype datatype, void *outbuf, MPI_Count outsize, MPI_Count *position, MPI_Comm comm) INPUT PARAMETERS inbuf - input buffer start (choice) incount - number of input data items (non-negative integer) datatype - datatype of each input data item (handle) outsize - output buffer size, in bytes (non-negative integer) comm - communicator for packed message (handle) INPUT/OUTPUT PARAMETERS position - current position in buffer, in bytes (integer) OUTPUT PARAMETERS outbuf - output buffer start (choice) NOTES (FROM THE SPECIFICATIONS) The input value of position is the first location in the output buffer to be used for packing. position is incremented by the size of the packed message, and the output value of position is the first location in the out- put buffer following the locations occupied by the packed message. The comm argument is the communicator that will be subsequently used for send- ing the packed message. 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_ARG - Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK ). 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_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. 4/10/2026 MPI_Pack(3)
NAME | SYNOPSIS | INPUT PARAMETERS | INPUT/OUTPUT PARAMETERS | OUTPUT PARAMETERS | NOTES (FROM THE SPECIFICATIONS) | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS
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