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.

                                                    2/9/2024                                  MPIX_Comm_agree(3)