# 17.2.253. MPI_Lookup_name

    MPI_Lookup_name - Finds port associated with a service name

## 17.2.253.1. SYNTAX

### 17.2.253.1.1. C Syntax

    #include <mpi.h>

    int MPI_Lookup_name(const char *service_name, MPI_Info info,
         char *port_name)

### 17.2.253.1.2. Fortran Syntax

    USE MPI
    ! or the older form: INCLUDE 'mpif.h'
    MPI_LOOKUP_NAME(SERVICE_NAME, INFO, PORT_NAME, IERROR)
         CHARACTER*(*)   SERVICE_NAME, PORT_NAME
         INTEGER         INFO, IERROR

### 17.2.253.1.3. Fortran 2008 Syntax

    USE mpi_f08
    MPI_Lookup_name(service_name, info, port_name, ierror)
         CHARACTER(LEN=*), INTENT(IN) :: service_name
         TYPE(MPI_Info), INTENT(IN) :: info
         CHARACTER(LEN=MPI_MAX_PORT_NAME), INTENT(OUT) :: port_name
         INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 17.2.253.2. INPUT PARAMETERS

- `service_name`: A service name (string).

- `info`: Options to the name service functions (handle).

## 17.2.253.3. OUTPUT PARAMETERS

- `port_name`: a port name (string).

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

## 17.2.253.4. DESCRIPTION

This function retrieves a port_name published under service_name by a previous invocation of MPI_Publish_name. The application must supply a port_name buffer large enough to hold the largest possible port name (i.e., MPI_MAX_PORT_NAME bytes).

## 17.2.253.5. INFO ARGUMENTS

The following keys for info are recognized:

    Key                   Type      Description
    ---                   ----      -----------

    ompi_lookup_order     char *    Resolution order for name lookup.

The ompi_lookup_order info key can specify one of four valid string values (see the NAME SCOPE section below for more information on name scopes):

local: Only search the local scope for name resolution.

global: Only search the global scope for name resolution.

local,global: Search the local scope for name resolution. If

  not found, try searching the global scope for name resolution. This behavior is the default if the ompi_lookup_order info key is not specified.

global,local: Search the global scope for name resolution. If

  not found, try searching the local scope for name resolution.

If no info key is provided, the search will first check to see if a global server has been specified and is available. If so, then the search will default to global scope first, followed by local. Otherwise, the search will default to local.

## 17.2.253.6. NAME SCOPE

Open MPI supports two name scopes: global and local. Local scope values are placed in a data store located on the mpirun of the calling process’ job, while global scope values reside on a central server. Calls to MPI_Unpublish_name must correctly specify the scope to be used in finding the value to be removed. The function will return an error if the specified service name is not found on the indicated location.

For a more detailed description of scoping rules, please see the MPI_Publish_name man page.

## 17.2.253.7. 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

- MPI_Publish_name

- MPI_Open_port