MPI_FREE_MEM(3)

💖 MPI_FREE_MEM(3) — bestie, it's Open MPI and we're freeing memory 💖

okay so. hi. you're here because you called MPI_Alloc_mem, you got your little block of memory, and now the vibe is over and you need to let it go. this is the page for that. it's MPI_Free_mem, from Open MPI, and honestly? it's giving "cleaning up after yourself, main character energy." 🎀

---

✨ SYNTAX ✨

💅 C Syntax

#include <mpi.h>

int MPI_Free_mem(void *base)

🦋 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_FREE_MEM(BASE, IERROR)
    <type> BASE(*)
    INTEGER IERROR

🌸 Fortran 2008 Syntax

USE mpi_f08

MPI_Free_mem(base, ierror)
    TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: base
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

---

🌈 INPUT PARAMETER

• base — the initial address of the memory segment that got allocated by MPI_Alloc_mem <#mpi-alloc-mem>. that's it, that's the one you're handing back. (type: choice.) 🫶

---

💜 OUTPUT PARAMETER

• ierror — Fortran only, babes: the error status, and it's an integer. 💫

---

👑 DESCRIPTION

okay so here's the whole thing, and it's not complicated:

MPI_Free_mem frees memory that has been allocated by MPI_Alloc_mem <#mpi-alloc-mem>.

that's the tea. you allocated with one, you free with the other. periodt. 🍓

---

💀 ERRORS 💀

buckle up bestie, this part is long but it's important, no cap.

Almost all MPI routines return an error value — C routines hand it back as the return result of the function, and Fortran routines put it in the last argument. MPI_Free_mem is no exception, so check your ierror in Fortran. 🙈

Before that error value ever gets returned, the current MPI error handler associated with the communication object (think: communicator, window, file) is called. and if there's no communication object associated with the MPI call? then the call is considered attached to MPI_COMM_SELF, and it will call the associated MPI error handler. when MPI_COMM_SELF is not initialized — meaning before MPI_Init <#mpi-init> / MPI_Init_thread <#mpi-init-thread>, after MPI_Finalize <#mpi-finalize>, or when you're using the Sessions Model exclusively — the error raises the initial error handler. and that initial error handler can be changed by:

• calling MPI_Comm_set_errhandler <#mpi-comm-set-errhandler> on MPI_COMM_SELF when you're using the World model, or
• the mpi_initial_errhandler CLI argument to mpiexec, or
• the info key to MPI_Comm_spawn <#mpi-comm-spawn> / MPI_Comm_spawn_multiple <#mpi-comm-spawn-multiple>.

and if no other appropriate error handler has been set, then MPI_ERRORS_RETURN is the handler that gets called for MPI I/O functions, and MPI_ERRORS_ABORT is the handler that gets called for all other MPI functions.

Open MPI ships three predefined error handlers you can use:

• 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 it's called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. if it's called on a window or a file, it acts as if MPI_Abort <#mpi-abort> was called on a communicator containing the group of processes in the corresponding window or file. and if it's called on a session, it aborts only the local process. 👀
• MPI_ERRORS_RETURN — returns an error code to the application. nice, gentle, we love her. 🫶

MPI applications can also implement their own error handlers by calling:

• MPI_Comm_create_errhandler <#mpi-comm-create-errhandler> and then MPI_Comm_set_errhandler <#mpi-comm-set-errhandler>
• MPI_File_create_errhandler <#mpi-file-create-errhandler> and then MPI_File_set_errhandler <#mpi-file-set-errhandler>
• MPI_Session_create_errhandler <#mpi-session-create-errhandler> and then MPI_Session_set_errhandler <#mpi-session-set-errhandler>, or at MPI_Session_init <#mpi-session-init>
• MPI_Win_create_errhandler <#mpi-win-create-errhandler> and then MPI_Win_set_errhandler <#mpi-win-set-errhandler>

⚠️ note that MPI does not guarantee that an MPI program can continue past an error. fr fr. plan accordingly. 💀

see the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

and see the Error Handling section of the MPI-3.1 standard for even more info, iykyk. 📚

---

🔥 SEE ALSO 🔥

• MPI_Alloc_mem <#mpi-alloc-mem> — because every free needs its alloc, bestie. they're a matched set. 💞

---

🎀 Copyright 🎀

2003-2026, The Open MPI Community ✨

---

and that's the whole page!! you freed your memory, you checked your error codes, you're thriving. this was MPI_FREE_MEM(3) from Open MPI, last touched Sep 10, 2026 — mwah, sending you a big Open MPI Community kiss, go forth and MPI_Free_mem responsibly 💖🦋🌸💅👑