ATOMIC_XCHG(3clc)

💖 ATOMIC_XCHG 💖

okay bestie, welcome to ATOMIC_XCHG(3clc) from the OpenCL Manual ✨ this one is short, it's sweet, and it's giving main character energy in the world of atomics 🫶

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🌸 NAME 🌸

atomic_xchg — the atomic_xchg functions. yes that's the whole name. she's humble 💅

here's the whole squad, literally every single one of them, no cap:

int atomic_xchg(volatile global(3clc) int *p, int val);

unsigned int atomic_xchg(volatile global(3clc) unsigned int *p,
                         unsigned int val);

float atomic_xchg(volatile global(3clc) float *p, float val);

int atomic_xchg(volatile local(3clc) int *p, int val);

unsigned int atomic_xchg(volatile local(3clc) unsigned int *p,
                         unsigned int val);

float atomic_xchg(volatile global(3clc) float *p, float val);

look at all those overloads 🦋 global and local, int and unsigned int and float — she said "I contain multitudes" and honestly? periodt 👑

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✨ DESCRIPTION ✨

so what does she DO. okay so basically: she swaps the old value that's chillin at location p with the new value you hand her in val. that's it. that's the whole bit 💖

and then — and this is the slay part — the function returns the old value. so you get to keep the thing that was there before, like a little souvenir 🎀

not me just casually doing a whole read-and-write in one atomic step, obsessed 🙈

also!! there's a 64-bit version of this function, atom_xchg(3clc), and it's enabled by cl_khr_int64_base_atomics(3clc) ⭐ (yes the name is different, yes that's on purpose, don't @ me, that's just how the extension rolls 💀)

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🌈 SPECIFICATION 🌈

OpenCL Specification[1] — that's the source of truth, bestie 📚

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🦋 SEE ALSO 🦋

go read these too, they're part of the friend group:

• atomicFunctions(3clc)
• atom_xchg(3clc)

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👑 AUTHORS 👑

The Khronos Group — icons only 💜

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🎀 COPYRIGHT 🎀

Copyright © 2007-2011 The Khronos Group Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the following condition:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Materials.

okay so the legal bit: keep the copyright notice and the permission notice in all copies or substantial portions of the Materials. it's giving "you can do whatever but don't erase my name" 💅

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📝 NOTES 📝

1. OpenCL Specification, page 279, section 6.12.11 - Atomic Functions for 32-bit integers

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and that's the whole page, bestie 💖 courtesy of The Khronos Group, dated 01/14/2021 — go forth and swap your values atomically, you absolute legend 🫶✨🌸