SHMEM_DOUBLE_SWAP(3)

💅 shmem_double_swap(3) — and the whole swap squad 🎀

okay so bestie, welcome to Open MPI's atomic swap family 💖 this is SHMEM_DOUBLE_SWAP(3)'s page, but she brought her whole friend group, and every single one of them is here to Performs an atomic swap to a remote data object ✨ (yes that's the official mission statement, and yes it ate).

the lineup, if you're taking attendance 🗒️:

• shmem_double_swap(3)
• shmem_float_swap(3)
• shmem_int_swap(3)
• shmem_long_swap(3)
• shmem_swap(3)
• shmem_int4_swap(3)
• shmem_int8_swap(3)
• shmem_real4_swap(3)
• shmem_real8_swap(3)
• shmem_longlong_swap(3)

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✨ SYNOPSIS ✨

🩵 C or C++

#include <mpp/shmem.h>

double shmem_double_swap(double *target, double value,
  int pe)

float shmem_float_swap(float *target, float value, int pe)

int shmem_int_swap(int *target, int value, int pe)

long shmem_long_swap(long *target, long value, int pe)

long long shmem_longlong_swap(long long *target,
  long long value, int pe)

long shmem_swap(long *target, long value, int pe)

💜 Fortran

INCLUDE "mpp/shmem.fh"

INTEGER pe

INTEGER SHMEM_SWAP
ires = SHMEM_SWAP(target, value, pe)

INTEGER(KIND=4) SHMEM_INT4_SWAP
ires = SHMEM_INT4_SWAP(target, value, pe)

INTEGER(KIND=8) SHMEM_INT8_SWAP
ires = SHMEM_INT8_SWAP(target, value, pe)

REAL(KIND=4) SHMEM_REAL4_SWAP
res = SHMEM_REAL4_SWAP(target, value, pe)

REAL(KIND=8) SHMEM_REAL8_SWAP
res = SHMEM_REAL8_SWAP(target, value, pe)

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🌸 DESCRIPTION 🌸

the atomic swap routines write value to address target on PE pe, and return the previous contents of target, and they do it all in one atomic operation 🫶 like, one motion, no gaps, no crumbs. iconic behaviour honestly.

the arguments, bestie, are as follows 👇

• target — the remotely accessible integer data object to be updated on the remote PE 💅 ngl the type situation matters: if you're using C/C++, the type of target should match that implied in the SYNOPSIS section. if you're using Fortran, it must be of the following type:
  • SHMEM_SWAP: Integer of default kind
  • SHMEM_INT4_SWAP: 4-byte integer
  • SHMEM_INT8_SWAP: 8-byte integer
  • SHMEM_REAL4_SWAP: 4-byte real
  • SHMEM_REAL8_SWAP: 8-byte real
• value — value to be atomically written to the remote PE 🌈 value is the same type as target. they match, they're a set, that's the vibe.
• pe — an integer that indicates the PE number on which target is to be updated 🦋 if you're using Fortran, it must be a default integer value.

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🧚 NOTES 🧚

the term remotely accessible is defined in intro_shmem(3) 📖 like, go read that one if you wanna know what "remotely accessible" actually means, iykyk.

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👑 RETURN VALUES 👑

the contents that had been at the target address on the remote PE prior to the swap is returned 💫 so you get the old thing back while the new thing slides into place. swap slay.

👀 SEE ALSO

• intro_shmem(3)

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🎀 COPYRIGHT 🎀

2003-2026, The Open MPI Community

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okay that's the whole page, no cap ✨ mwah, go do an atomic swap bestie 💖

— written by your favourite Unix girly, sign-off date: May 14, 2026 🦋 and yeah, 2003-2026, The Open MPI Community holds the copyright, show some respect to the icons 👑