NAME

       MPIX_Comm_agree -  Performs agreement operation on comm

SYNOPSIS

       int MPIX_Comm_agree(MPI_Comm comm, int *flag)

INPUT PARAMETERS

       comm   - communicator (handle)

OUTPUT PARAMETERS

       flag   - 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.

       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  communicator  in  a  call
              (not even allowed in MPI_Comm_rank ).
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

                                            2/22/2022                          MPIX_Comm_agree(3)