MPI_Publish_name - Publishes a service name associated with a port
int MPI_Publish_name(char *service_name, MPI_Info info,
MPI_PUBLISH_NAME(SERVICE_NAME, INFO, PORT_NAME, IERROR)
CHARACTER*(*) SERVICE_NAME, PORT_NAME
INTEGER INFO, IERROR
void MPI::Publish_name(const char* service_name, const MPI::Info& info,
const char* port_name)
service_name A service name (string).
info Options to the name service functions (handle).
port_name A port name (string).
IERROR Fortran only: Error status (integer).
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.
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.
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
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.
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.