# 17.2.53. MPI_Comm_delete_attr

MPI_Comm_delete_attr — Deletes attribute value associated with a key.

## 17.2.53.1. SYNTAX

### 17.2.53.1.1. C Syntax

    #include <mpi.h>

    int MPI_Comm_delete_attr(MPI_Comm comm, int comm_keyval)

### 17.2.53.1.2. Fortran Syntax

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

    MPI_COMM_DELETE_ATTR(COMM, COMM_KEYVAL, IERROR)
        INTEGER COMM, COMM_KEYVAL, IERROR

### 17.2.53.1.3. Fortran 2008 Syntax

    USE mpi_f08

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

### 17.2.53.1.4. INPUT/OUTPUT PARAMETER

- `comm` : Communicator from which the attribute is deleted (handle).

## 17.2.53.2. INPUT PARAMETER

- `comm_keyval` : Key value (integer).

## 17.2.53.3. OUTPUT PARAMETER

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

## 17.2.53.4. DESCRIPTION

MPI_Comm_delete_attr deletes an attribute from cache by key. This function invokes the attribute delete function `delete_fn` specified when the `comm_keyval` was created. The call will fail if the `delete_fn` function returns an error code other than `MPI_SUCCESS`.

Whenever a communicator is replicated using the function MPI_Comm_dup, all callback copy functions for attributes that are currently set are invoked (in arbitrary order). Whenever a communicator is deleted using the function MPI_Comm_free, all callback delete functions for attributes that are currently set are invoked. This function is the same as MPI_Attr_delete but is needed to match the `comm`unicator-specific functions introduced in the MPI-2 standard. The use of MPI_Attr_delete is deprecated.

## 17.2.53.5. NOTES

Note that it is not defined by the MPI standard what happens if the `delete_fn` callback invokes other MPI functions. In Open MPI, it is not valid for `delete_fn` callbacks (or any of their children) to add or delete attributes on the same object on which the `delete_fn` callback is being invoked.

## 17.2.53.6. 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.