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

NAME

       MPI_Publish_name - Publishes a service name associated with a port

SYNTAX

C Syntax

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

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_PUBLISH_NAME(SERVICE_NAME, INFO, PORT_NAME, IERROR)
            CHARACTER*(*)  SERVICE_NAME, PORT_NAME
            INTEGER        INFO, 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.

       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.