Scroll to navigation

MPIX_Comm_agree(3) MPI MPIX_Comm_agree(3)

NAME

MPIX_Comm_agree - Performs agreement operation on comm

SYNOPSIS



int MPIX_Comm_agree(MPI_Comm comm, int *flag)










INPUT PARAMETERS



  

  
- communicator (handle)
    

  








OUTPUT PARAMETERS



  

  
- new communicator (logical)
    

  








NOTES


The purpose of this collective communication is to agree on the
    integer value flag and on the group of failed processes in comm.


On completion, all non-failed MPI processes have agreed to set the
    output integer value of flag to the result of a bitwise AND operation over
    the contributed input values of flag. If comm is an intercommunicator, the
    value of flagis a bitwise AND operation over the values contributed by the
    remote group.


When an MPI process fails before contributing to the operation,
    the flag is computed ignoring its contribution, and MPIX_Comm_agree raises
    an error of class MPI_ERR_PROC_FAILED. However, if all MPI processes have
    acknowledged this failure priorto the call to MPIX_Comm_agree, using
    MPIX_Comm_failure_ack, the error related to this failure is not raised. When
    an error of class MPI_ERR_PROC_FAILED is raised, it is consistently raised
    at allMPI processes, in both the local and remote groups (if
  applicable).


After MPIX_Comm_agree raised an error of class
    MPI_ERR_PROC_FAILED, a subse-quent call to MPIX_Comm_failure_ack on comm
    acknowledges the failure of every MPI process that didn t contribute to
    the computation offlag.








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 integer 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 statement.


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 argument. Before the value is returned, the
    current MPI error handler is called. By default, this error handler aborts
    the MPI job. The error handler 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.





  

  
- No error; MPI routine completed successfully.

  

  
- Invalid argument. Some argument is invalid and is not identified by a
      specific error class (e.g., MPI_ERR_RANK ).

  

  
- Invalid communicator. A common error is to use a null communicator in a
      call (not even allowed in MPI_Comm_rank ).

  

  
- Other error; use MPI_Error_string to get more information about
      this error code.
    

  









  

    2/9/2024