MPI_LOOKUP_NAME(3)

💅 MPI_LOOKUP_NAME(3) — the Open MPI page, but make it make sense ✨

okay so we're in the Open MPI manual, on the MPI_LOOKUP_NAME(3) page, and bestie this one is genuinely useful — it's literally how you go find your friend's port by name 🫶

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🌸 NAME 🌸

MPI_Lookup_name — finds port associated with a service name

like, you gave your service a name, now go get the port back. iconic behavior.

✨ SYNTAX ✨

💖 C Syntax

#include <mpi.h>

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

💖 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

💖 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

🎀 INPUT PARAMETERS 🎀

• service_name — a service name (string). as in, the name you're searching for 💅
• info — options to the name service functions (handle).

🦋 OUTPUT PARAMETERS 🦋

• port_name — a port name (string). this is the thing you came for 🎁
• ierror — Fortran only: error status (integer).

💫 DESCRIPTION 💫

This function retrieves a port_name published under service_name by a previous invocation of MPI_Publish_name.

🚨 buffer check, bestie 🚨 the application must supply a port_name buffer large enough to hold the largest possible port name (i.e., MPI_MAX_PORT_NAME bytes). do not skimp on this, i am begging 🙏

👑 INFO ARGUMENTS 👑

The following keys for info are recognized:

• range — type char * — Scope in which to search for the service name. See the NAME SCOPE section below.

The range info key accepts one of two string values:

• nspace — Restrict the operation to processes in the same MPI job (PMIx namespace) as the calling process.
• session — Apply the operation across all processes in the same session.

If the info argument is MPI_INFO_NULL, or is a valid info object that does not contain a range key, session scope is used. Because MPI_Publish_name, MPI_Lookup_name, and MPI_Unpublish_name all share this default, a name published with MPI_INFO_NULL is found by a lookup with MPI_INFO_NULL. (consistency slay 💖)

Any other value for range results in an error. no cap, it will simply not work.

🌈 NAME SCOPE 🌈

Open MPI supports two name scopes, selected by the range info key: nspace and session.

nspace scope restricts the (service_name, port_name) pair to processes in the publisher's own MPI job, i.e., processes sharing the publisher's PMIx namespace.

session scope makes the pair visible to every process in the same PMIx session. This includes jobs started by separate mpirun invocations that share a persistent DVM or scheduler allocation, as well as jobs created via MPI_Comm_spawn. session is the default scope. main character energy tbh 👑

The same scope must be used to publish, look up, and unpublish a given service name. MPI_Unpublish_name returns an error if the service name is not found in the indicated scope.

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

💀 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. like, it might just end. fr fr.

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

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📜 COPYRIGHT

2003-2026, The Open MPI Community

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and that's the whole page, bestie 💜 shoutout to the Open MPI girlies — this edition is from Sep 11, 2026, copyright 2003-2026, The Open MPI Community 🎀 go publish a name and find it again, you've got this 🦋✨