MPI_Get_count(3) MPI MPI_Get_count(3) NAME MPI_Get_count - Gets the number of "top level" elements SYNOPSIS int MPI_Get_count(const MPI_Status *status, MPI_Datatype datatype, int *count) int MPI_Get_count_c(const MPI_Status *status, MPI_Datatype datatype, MPI_Count *count) INPUT PARAMETERS status - return status of receive operation (Status) datatype - datatype of each receive buffer entry (handle) OUTPUT PARAMETERS count - number of received entries (integer) NOTES If the size of the datatype is zero, this routine will return a count of zero. If the amount of data in status is not an exact multiple of the size of datatype (so that count would not be integral), a count of MPI_UNDEFINED is returned instead. 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_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_Get_count(3)
NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETERS | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS
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