Ubuntu Manpage: MPI_Publish_name - Publishes a service name associated with a port

Provided by: openmpi-doc_4.1.6-7ubuntu2_all

NAME

       MPI_Publish_name - Publishes a service name associated with a port

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Publish_name(const char *service_name, MPI_Info info,
            const char *port_name)

Fortran Syntax

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

Fortran 2008 Syntax

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

C++ Syntax

       #include <mpi.h>
       void MPI::Publish_name(const char* service_name, const MPI::Info& info,
            const char* port_name)

INPUT PARAMETERS

       service_name  A service name (string).

       info          Options to the name service functions (handle).

       port_name     A port name (string).

OUTPUT PARAMETER

       IERROR        Fortran only: Error status (integer).

DESCRIPTION

       This  routine  publishes the pair (service_name, port_name) so that an application may retrieve port_name
       by calling MPI_Lookup_name with service_name as  an  argument.  It  is  an  error  to  publish  the  same
       service_name  twice, or to use a port_name argument that was not previously opened by the calling process
       via a call to MPI_Open_port.

INFO ARGUMENTS

       The following keys for info are recognized:

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

       ompi_global_scope     bool      If set to true, publish the name in
                                       the global scope.  Publish in the local
                                       scope otherwise.  See the NAME SCOPE
                                       section for more details.

       ompi_unique           bool      If set to true, return an error if the
                                       specified service_name already exists.
                                       Default to overwriting any pre-existing
                                       value.

       bool info keys are actually strings but are evaluated as follows: if the string value is a number, it  is
       converted  to  an integer and cast to a boolean (meaning that zero integers are false and non-zero values
       are true).  If the string value is (case-insensitive) "yes" or "true",  the  boolean  is  true.   If  the
       string  value  is  (case-insensitive) "no" or "false", the boolean is false.  All other string values are
       unrecognized, and therefore false.

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

NAME SCOPE

Open MPI supports two name scopes: global and local. Local scope will place the specified service/port
pair in a data store located on the mpirun of the calling process' job. Thus, data published with local
scope will only be accessible to processes in jobs spawned by that mpirun - e.g., processes in the
calling process' job, or in jobs spawned via MPI_Comm_spawn.

Global scope places the specified service/port pair in a data store located on a central server that is
accessible to all jobs running in the cluster or environment. Thus, data published with global scope can
be accessed by multiple mpiruns and used for MPI_Comm_Connect and MPI_Comm_accept between jobs.

Note that global scope operations require both the presence of the central server and that the calling
process be able to communicate to that server. MPI_Publish_name will return an error if global scope is
specified and a global server is either not specified or cannot be found.

Open MPI provides a server called ompi-server to support global scope operations. Please refer to its
manual page for a more detailed description of data store/lookup operations.

As an example of the impact of these scoping rules, consider the case where a job has been started with
mpirun - call this job "job1". A process in job1 creates and publishes a service/port pair using a local
scope. Open MPI will store this data in the data store within mpirun.

A process in job1 (perhaps the same as did the publish, or perhaps some other process in the job)
subsequently calls MPI_Comm_spawn to start another job (call it "job2") under this mpirun. Since the two
jobs share a common mpirun, both jobs have access to local scope data. Hence, a process in job2 can
perform an MPI_Lookup_name with a local scope to retrieve the information.

However, assume another user starts a job using mpirun - call this job "job3". Because the service/port
data published by job1 specified local scope, processes in job3 cannot access that data. In contrast, if
the data had been published using global scope, then any process in job3 could access the data, provided
that mpirun was given knowledge of how to contact the central server and the process could establish
communication with it.

ERRORS

       Almost all MPI routines return an error value; C routines as  the  value  of  the  function  and  Fortran
       routines in the last argument. C++ functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS,  then  on  error  the  C++  exception  mechanism  will  be used to throw an
       MPI::Exception object.

       Before the error value is returned, the current MPI error handler  is  called.  By  default,  this  error
       handler  aborts  the  MPI  job,  except  for  I/O  function errors. The error handler may be changed with
       MPI_Comm_set_errhandler; 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.

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