MPI_INFO_GET_VALUELEN(3)

📦
version 5.0.10 · 7 versions
, in ubuntu stonking

💖 MPI_INFO_GET_VALUELEN 💖

okay bestie, so this one's an Open MPI situation — welcome to the MPI_Info_get_valuelen page, and no cap, it's lowkey one of the simpler ones, which honestly? we love that for us. ✨

✨ NAME ✨

MPI_Info_get_valuelen — bestie, this is the girl that retrieves the length of the key value associated with an info object. Just the length, mind you. Not the value itself. She's not nosy like that. 💅

🦋 SYNTAX 🦋

C Syntax

#include <mpi.h>

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

Fortran Syntax

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

Fortran 2008 Syntax

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

🌸 INPUT PARAMETERS 🌸

  • info — the Info object, aka the handle. that's her 🫶
  • key — the key, as a string. the search term, the main character 🔍

🎀 OUTPUT PARAMETERS 🎀

  • valuelen — the length of the value arg, as an integer. literally just a number bestie 📏
  • flag — returns true if the key is defined, false if it's not. boolean behaviour, very demure ✨
  • ierror — Fortran only: the error status, as an integer. the Fortran girlies get their own lil slot 💜

🔥 DESCRIPTION 🔥

So MPI_Info_get_valuelen retrieves the length of the value associated with key. Simple as that.

Here's the tea though, and pay attention because it's a vibe check moment:

  • If key is defined, valuelen gets set to the length of its associated value, and flag gets set to true. slay ✅
  • If key is not defined, valuelen is not touched — she stays exactly as she was, no notes, no edits — and flag gets set to false. don't even look at her 🙈

Also, important: the length returned in C does not include the end-of-string character. that extra lil byte is not invited to the count, periodt. 💅

⚠️ and if key is larger than MPI_MAX_INFO_KEY, the call is erroneous. not "oopsie", not "we'll figure it out" — erroneous. don't do it. 🚩

😭 ERRORS 😭

Okay so almost all MPI routines return an error value, right? C routines hand it back as the return result of the function, and Fortran routines put it in the last argument. that's the split, iykyk.

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. 😮‍💨

👑 the three predefined error handlers Open MPI ships with 👑

  • MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. she said everyone's coming with her 💀
  • 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. very context-aware of her ngl
  • MPI_ERRORS_RETURN — returns an error code to the application. the chill one, she just hands you the receipt 🧾

✨ and you can also write your own, because DIY is iconic ✨

MPI applications can 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, it might just be over 💀

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_Info_get
  • MPI_Info_get_nkeys
  • MPI_Info_get_nthkey

2003-2026, The Open MPI Community

and that's the whole page, bestie!! 💖 this lil baddie is dated Sep 10, 2026, it comes from the Open MPI crew, and it lives in the manual as MPI_INFO_GET_VALUELEN(3). go get those lengths, you absolute icon 👑✨🦋

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