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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
       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 out-
       put 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, us-
       ing  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 com-
       municators),  MPI_File_set_errhandler  (for files), and MPI_Win_set_er-
       rhandler	(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	 when-
       ever possible.

       MPI_SUCCESS
	      -	No error; MPI routine completed	successfully.
       MPI_ERR_ARG
	      -	Invalid	argument.  Some	argument is invalid and	is not identi-
	      fied by a	specific error class (e.g., MPI_ERR_RANK ).
       MPI_ERR_COMM
	      -	 Invalid communicator.	A common error is to use a null	commu-
	      nicator 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.

				   2/3/2025		    MPIX_Comm_agree(3)

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