MPI_INFO_GET(3)

💖 MPI_INFO_GET(3) — Open MPI, bestie edition ✨

Okay so this is a page from the Open MPI manual, and it's all about MPI_Info_get, which is literally the ✨lookup era✨ of info objects. Buckle up, we're fetching values 🎀

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🌸 NAME 🌸

MPI_Info_get — retrieves the value associated with a key in an info object. That's it, that's the whole vibe 🫶

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✨ SYNTAX ✨

🦋 C Syntax

#include <mpi.h>

int MPI_Info_get(MPI_Info info, const char *key, int valuelen, char *value, int *flag)

🦋 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_INFO_GET(INFO, KEY, VALUELEN, VALUE, FLAG, IERROR)
     INTEGER INFO, VALUELEN, IERROR
     CHARACTER*(*) KEY, VALUE
     LOGICAL FLAG

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Info_get(info, key, valuelen, value, flag, ierror)
     TYPE(MPI_Info), INTENT(IN) :: info
     CHARACTER(LEN=*), INTENT(IN) :: key
     INTEGER, INTENT(IN) :: valuelen
     CHARACTER(LEN=valuelen), INTENT(OUT) :: value
     LOGICAL, INTENT(OUT) :: flag
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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💅 INPUT PARAMETERS 💅

• info — the info object, aka the handle. Your little info bag 👜
• key — the key, as a string. The thing you're searching for 🔍
• valuelen — the length of the value arg (integer). Basically how much room you're giving it to write into 📏

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🎀 OUTPUT PARAMETER 🎀

• value — the value, as a string. This is where the tea gets poured ☕
• flag — returns true if the key is defined, false if it's not (boolean). A whole vibe check in one variable 💀
• ierror — Fortran only: error status (integer) 🧚

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💜 DESCRIPTION 💜

So MPI_Info_get retrieves the value associated with key from a previous call to MPI_Info_set. Iconic callback energy 👑

If such a key exists, it sets flag to true and returns the value in value. If it does not exist, it sets flag to false and leaves value unchanged — like, it does not touch it, no notes 😭

valuelen is the number of characters available in value. If it's less than the actual size of the value, the returned value is truncated. Yes, it will just chop it. Be aware 🫣

In C, valuelen should be one less than the amount of allocated space to allow for the null terminator. Do not forget the null terminator, bestie, it's giving classic C behavior 💀

If key is larger than MPI_MAX_INFO_KEY, the call is erroneous. So keep your keys within MPI_MAX_INFO_KEY, periodt ✋

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🔥 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. Same as always 💫

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. Yeah. All of them. 💀
• 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, it 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, it aborts only the local process. 🫠
• MPI_ERRORS_RETURN — returns an error code to the application. The chill one 🫶

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, no promises, bestie 😬

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.

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👀 SEE ALSO 👀

• MPI_Info_create
• MPI_Info_delete
• MPI_Info_dup
• MPI_Info_free
• MPI_Info_get_valuelen
• MPI_Info_get_nkeys
• MPI_Info_get_nthkey
• MPI_Info_set

Like the whole info-object friend group, honestly 🫶✨

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🍓 COPYRIGHT 🍓

2003-2026, The Open MPI Community

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And that's the page, bestie!! 🎀 This one's dated Sep 11, 2026 and comes to you from The Open MPI Community — stan them, they wrote the whole thing 💖 Go get those info values, you're gonna slay 🦋✨