# 18.2.474. MPIX_Comm_revoke

MPIX_Comm_revoke - Revoke a communicator, causing errors to be raised, at all ranks, for non-local operations on the communicator.

This is part of the User Level Fault Mitigation ULFM extension.

## 18.2.474.1. SYNTAX

### 18.2.474.1.1. C Syntax

    #include <mpi.h>
    #include <mpi-ext.h>

    int MPIX_Comm_revoke(MPI_Comm comm)

### 18.2.474.1.2. Fortran Syntax

    USE MPI
    USE MPI_EXT
    ! or the older form: INCLUDE 'mpif.h'

    MPIX_COMM_REVOKE(COMM, IERROR)
         INTEGER COMM, IERROR

### 18.2.474.1.3. Fortran 2008 Syntax

    USE mpi_f08
    USE mpi_ext_f08

    MPIX_Comm_revoke(comm, ierror)
         TYPE(MPI_Comm), INTENT(IN) :: comm
         INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 18.2.474.2. INPUT PARAMETERS

- `comm`: Communicator (handle).

## 18.2.474.3. OUTPUT PARAMETERS

- `ierror`: Fortran only: Error status (integer).

## 18.2.474.4. DESCRIPTION

This function marks the communicator comm as revoked at all MPI processes in the groups (local and remote) associated with the communicator comm. This function is not collective and therefore does not have a matching call on remote MPI processes.

The documentation for MPIX_Comm_is_revoked details the conditions for when a communicator becomes revoked locally, and what semantics apply on a revoked communicator. In summary, when a communicator is revoked, non-local operation raise an exception of class MPIX_ERR_REVOKED, except for select fault-tolerant operations.

## 18.2.474.5. PROPAGATION OF THE REVOKED STATE AND ORDERING

The implementation propagates the revoked state in a fault-tolerant manner; thus, the communicator becomes revoked at all non-failed MPI processes belonging to comm despite failed processes.

There is no particular ordering between the revocation call at another process and the completion of operations at a local process, for example, a receive operation can raise an error of class MPIX_ERR_REVOKED, even if the send operation procedure is called before the revoke procedure at the sender.

## 18.2.474.6. ERRORS

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

- `MPI_ERRORS_ARE_FATAL` Causes the program to abort all connected MPI processes.

- `MPI_ERRORS_ABORT` An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.

- `MPI_ERRORS_RETURN` Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

- MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

- MPI_File_create_errhandler then MPI_File_set_errhandler

- MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

- MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.

See also

- MPIX_Comm_is_revoked

- MPIX_Comm_agree

- MPIX_Comm_shrink