MPI_T_PVAR_HANDLE_ALLOC(3)

💅 MPI_T_PVAR_HANDLE_ALLOC 💅

okay bestie, so this one is from Open MPI — the manual page is literally called MPI_T_PVAR_HANDLE_ALLOC(3) and it's about the two functions MPI_T_pvar_handle_alloc and MPI_T_pvar_handle_free. They do exactly what the names say: one allocates MPI performance variable handles, the other frees them. iconic duo tbh 🫶

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✨ NAME ✨

MPI_T_pvar_handle_alloc, MPI_T_pvar_handle_free — Allocate/free MPI performance variable handles. yes that's the whole name section, we keep it cute and we keep it accurate 💖

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🎀 SYNTAX 🎀

C Syntax 🌸

#include <mpi.h>

int MPI_T_pvar_handle_alloc(int session, int pvar_index, void *obj_handle,
                            MPI_T_pvar_handle *handle, int *count)

int MPI_T_pvar_handle_free(int session, MPI_T_pvar_handle *handle)

like, copy that exactly, no cap, don't be editing the signature 🙈

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🦋 DESCRIPTION 🦋

so MPI_T_pvar_handle_alloc does this thing where it binds the performance variable you named in pvar_index to the MPI object you named in obj_handle, inside the session identified by the parameter session. the way that works is — the object gets passed in the argument obj_handle as an address to a local variable that stores the object's handle. sneaky but correct 💅

and listen: if MPI_T_pvar_get_info returns MPI_T_BIND_NO_OBJECT as the binding for the variable, then the obj_handle argument is ignored. just vibes at that point, ok?

the handle that gets allocated to reference the variable comes back to you in the argument handle. and upon successful return, count contains the number of elements (of the datatype returned by a previous MPI_T_pvar_get_info call) used to represent this variable. so count is not random, it's derived, periodt ✨

the value of pvar_index should be in the range 0 to num_pvar - 1, where num_pvar is the number of available performance variables as determined from a prior call to MPI_T_pvar_get_num. the type of the MPI object it references must be consistent with the type returned in the bind argument in a prior call to MPI_T_pvar_get_info. no mismatches, bestie, that's the vibe check 🔥

then MPI_T_pvar_handle_free frees a handle allocated by MPI_T_pvar_handle_alloc and sets the handle argument to MPI_T_PVAR_HANDLE_NULL. clean exit, main character energy 👑

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💀 ERRORS 💀

good news: these fail in very documented ways. bad news: they do fail 😭

🙈 MPI_T_pvar_handle_alloc will fail if:

• MPI_T_ERR_NOT_INITIALIZED — The MPI Tools interface not initialized (girl, you gotta init first)
• MPI_T_ERR_INVALID_INDEX — The performance variable index is invalid
• MPI_T_ERR_OUT_OF_HANDLES — No more handles available (sold out, try again later 💀)

🍓 MPI_T_pvar_handle_free will fail if:

• MPI_T_ERR_NOT_INITIALIZED — The MPI Tools interface not initialized
• MPI_T_ERR_INVALID_HANDLE — The handle is invalid or the handle argument passed in is not associated with the session argument (aka you brought the wrong handle to the wrong session, awkward 🫠)

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🌈 SEE ALSO 🌈

• MPI_T_pvar_get_info — go read this one, it's giving prerequisite 💖
• MPI_T_pvar_get_num — this one too, you literally need the number of vars from it

iykyk, these two are the ones you hit up before this page even makes sense ⭐

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community 💜

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k that's the whole page, slay, go allocate responsibly 🧚✨

signed off with love by the Open MPI girlies, dated Sep 11, 2026 — same page header and footer, just way more fun 🌸💅