SHMEM_LONGLONG_ADD(3)

💖 NAME 💖

okay so bestie, welcome to SHMEM_LONGLONG_ADD(3) from Open MPI — the atomic-add page, and yes she has many aliases because one name was simply not enough for her.

The whole girl squad of "add value to a thing, atomically":

• shmem_int_add
• shmem_int4_add
• shmem_int8_add
• shmem_long_add
• shmem_longlong_add

…and they all do ONE thing: perform an atomic add operation. that's it. that's the whole personality. 💅

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✨ SYNOPSIS ✨

C or C++:

#include <mpp/shmem.h>

void shmem_int_add(int *target, int value, int pe)
void shmem_long_add(long *target, long value, int pe)
void shmem_longlong_add(long long *target, long long value,
  int pe)

Fortran:

include 'mpp/shmem.h'

INTEGER pe

CALL SHMEM_INT4_ADD(target, value, pe)
CALL SHMEM_INT8_ADD(target, value, pe)

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🎀 DESCRIPTION 🎀

so the atomic add routines literally just add value to the data sitting at address target on PE pe. and here's the iconic part, the main character energy: the operation completes without the possibility of another process updating target between the time of the fetch and the update. no interlopers. no sneaky concurrent writes. it's giving locked in. 🔥

the arguments, let's go:

• target — the remotely accessible integer data object that's getting updated on the remote PE. iykyk: if you're in C/C++, the type of target should match what's implied in the SYNOPSIS section up there. if you're in Fortran, it must be of type integer with an element size of 4 bytes for SHMEM_INT4_ADD and 8 bytes for SHMEM_INT8_ADD. get those sizes right or don't come to the function call. 🫶
• value — the value being atomically added to target. C/C++ bestie? type should match the SYNOPSIS section. Fortran bestie? it must be of type integer with an element size of target. 💖
• pe — an integer that says which PE number target is going to be updated on. Fortran girlies: it must be a default integer value. ✨

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📝 NOTES 📝

quick vocab check: the term remotely accessible is defined over in intro_shmem(3). go read her, she's the lore.

See also:

• intro_shmem(3)
• shmem_cache(3)

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👑 Copyright 👑

2003-2026, The Open MPI Community

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and that's the page, bestie!! 🦋🌸✨ this was SHMEM_LONGLONG_ADD(3) from Open MPI, dropped on Sep 10, 2026 — slay, now go atomically add something. periodt. 💅💖