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)
- 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.
SEE ALSO¶
MPI_Lookup_name
MPI_Open_port