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Groups > sci.physics.relativity > #671512

There is no imageAtomicAdd in WGSL (Was: I didn't find Futex in WebGPU / WGSL)

From Mild Shock <janburse@fastmail.fm>
Newsgroups sci.physics.relativity, sci.math
Subject There is no imageAtomicAdd in WGSL (Was: I didn't find Futex in WebGPU / WGSL)
Date 2026-07-21 00:12 +0200
Message-ID <113m6gm$561a$1@solani.org> (permalink)
References (4 earlier) <113kfb6$3b4e$1@solani.org> <113m147$1frvv$1@dont-email.me> <113m3no$5496$1@solani.org> <113m45s$1gup3$1@dont-email.me> <113m4bi$1gvs1$1@dont-email.me>

Cross-posted to 2 groups.

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Hi,

Hi,

I am developing agains WebGPU / WGSL.
And overview of WebGPU / WGSL is found here:

https://github.com/webgpu/webgpufundamentals

There is no imageAtomicAdd in WGSL.
imageAtomicAdd is from WebGL / GLSL.

These are two different things:

WebGPU / WGSL : Wrapper for Vulcan, Direct 12, or Metal
WebGL / GLSL : Wrapper for OpenGL

Chris M. Thomasson schrieb:
> On 7/20/2026 2:32 PM, Chris M. Thomasson wrote:
>> On 7/20/2026 2:25 PM, Mild Shock wrote:
>>> Hi,
>>>
>>> I didn't find Futex in WebGPU / WGSL.
>>> The website WebGPU fundamentals is on
>>> GitHub. I did a search here:
>>>
>>> https://github.com/webgpu/webgpufundamentals
>>>
>>> In Java I can use Doug Leas queue.
>>> In WebGPU / WGSL I will mostlikely
>>> adopt Dmitry Vyukov , for a first stab.
>>>
>>> Who is Doug lea?
>>>
>>> He wrote Concurrent Programming in
>>> Java: Design Principles and Patterns
>>> https://en.wikipedia.org/wiki/Doug_Lea
>>
>> A futex:
>>
>> https://www.man7.org/linux/man-pages/man2/futex.2.html
>>
>> For a compute shader? Afaict, no need for it at all. Actually, strive 
>> to avoid any atomic RMW! It can be done, but if you really need it:
>>
>> imageAtomicAdd is a damn good one for accumulation buffers.
>>
>> An example from some of my compute shader code:
>>
>> void add_hit(ct_plane2d plane, vec2 p, vec3 weight)
>> {
>>      vec2 uv = ct_plane2d_unproject(plane, p);
>>      ivec2 px = ivec2(uv * u_resolution);
>>
>>      if (px.x >= 0 && px.x < int(u_resolution.x) &&
>>          px.y >= 0 && px.y < int(u_resolution.y))
>>      {
>>          imageAtomicAdd(accum_r,    px, weight.r);
>>          imageAtomicAdd(accum_g,    px, weight.g);
>>          imageAtomicAdd(accum_b,    px, weight.b);
>>          imageAtomicAdd(accum_hits, px, 1.0f);
>>      }
>> }
>>
>> [...]
> 
> You don't really want to "wait" for anything in a compute shader. If you 
> must use CAS use it as a state machine. Not a damn loop. If you can 
> manage it.

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  Corr.: Re: I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM] (Was: Paul Tarau versus Mr. Taskmanager, who would win? [A PDP-11 Humunkulus from 1979]) Mild Shock <janburse@fastmail.fm> - 2026-07-19 11:55 +0200
  Re: I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM] (Was: Paul Tarau versus Mr. Taskmanager, who would win? [A PDP-11 Humunkulus from 1979]) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-19 14:04 -0700
    Re: I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM] (Was: Paul Tarau versus Mr. Taskmanager, who would win? [A PDP-11 Humunkulus from 1979]) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-19 14:07 -0700
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        Re: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov (Was: I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM]) Romelio Balakhonsky <lrel@lao.ru> - 2026-07-20 10:07 +0000
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                Re: My Swift Go 16 AI has no IMEI, are you nuts? (Was: Even dogs know Switzerland != Germany [Syphilis Brain Micro Penis]) Randolf Mukanov <mfroa@unvfo.ru> - 2026-07-22 12:27 +0000
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                Re: I have nothing to hide, you can find me in search.ch (Was: My Swift Go 16 AI has no IMEI, are you nuts?) Keiv Babenchikov <hi@babebek.ru> - 2026-07-22 12:35 +0000
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        Re: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov (Was: I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM]) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-20 13:40 -0700
          I didn't find Futex in WebGPU / WGSL (Was: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov) Mild Shock <janburse@fastmail.fm> - 2026-07-20 23:25 +0200
            Re: I didn't find Futex in WebGPU / WGSL (Was: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-20 14:32 -0700
              Re: I didn't find Futex in WebGPU / WGSL (Was: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-20 14:35 -0700
                There is no imageAtomicAdd in WGSL (Was: I didn't find Futex in WebGPU / WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 00:12 +0200
                OpenGL is dead. Apple said bye bye / Wayland Compositor (Was: There is no imageAtomicAdd in WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 00:24 +0200
                Re: There is no imageAtomicAdd in WGSL (Was: I didn't find Futex in WebGPU / WGSL) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-20 16:15 -0700
                Flogging a Dead Horse, OpenGL is EOL (Was: There is no imageAtomicAdd in WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:24 +0200
                imageAtomicAdd trivial, Dmitry Vyukov requires capacity (Re: Flogging a Dead Horse, OpenGL is EOL (Was: There is no imageAtomicAdd in WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:32 +0200
                capacity = 2^n for some n / systolic system (Was: imageAtomicAdd trivial, Dmitry Vyukov requires capacity) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:37 +0200
                Source of the benchmark for DmitryVyukov (Re: capacity = 2^n for some n / systolic system) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:45 +0200
                Re: imageAtomicAdd trivial, Dmitry Vyukov requires capacity (Re: Flogging a Dead Horse, OpenGL is EOL (Was: There is no imageAtomicAdd in WGSL) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-20 17:00 -0700
                I never used OpenGL Version 4.2 and later (Re: imageAtomicAdd trivial, Dmitry Vyukov requires capacity) Mild Shock <janburse@fastmail.fm> - 2026-07-21 08:49 +0200
                Because of MIMD you have to reassess algorithms (Was: I never used OpenGL Version 4.2 and later) Mild Shock <janburse@fastmail.fm> - 2026-07-21 08:59 +0200
                Why MIMD is interesting for pi-WAM? Mild Shock <janburse@fastmail.fm> - 2026-07-21 09:16 +0200
                Re: Why MIMD is interesting for pi-WAM? Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-21 00:32 -0700
                Re: Because of MIMD you have to reassess algorithms (Was: I never used OpenGL Version 4.2 and later) Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-21 00:42 -0700
                You still don't understand "budget" [Rossy Boy slower than Micro Penis] (Was: Because of MIMD you have to reassess algorithms) Mild Shock <janburse@fastmail.fm> - 2026-07-21 10:13 +0200
                Go on Rossy Boy, ask more stupid questions (Was: You still don't understand "budget" [Rossy Boy slower than Micro Penis]) Mild Shock <janburse@fastmail.fm> - 2026-07-21 10:17 +0200
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                Re: Go on Rossy Boy, ask more stupid questions (Was: You still don't understand "budget" [Rossy Boy slower than Micro Penis]) Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-21 08:59 -0700
                Rossy Boy says I am a crazy frothing lunatic (Was: Go on Rossy Boy, ask more stupid questions) Mild Shock <janburse@fastmail.fm> - 2026-07-21 22:27 +0200
                Re: Rossy Boy says I am a crazy frothing lunatic (Was: Go on Rossy Boy, ask more stupid questions) Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-21 13:52 -0700
                Do you see the loops, in C code and in Java code? /** Looping **/ (Re: Because of MIMD you have to reassess algorithms) Mild Shock <janburse@fastmail.fm> - 2026-07-23 00:10 +0200
                Re: Do you see the loops, in C code and in Java code? /** Looping **/ (Re: Because of MIMD you have to reassess algorithms) Lane W <cactus_DAC@yahoo.com> - 2026-07-22 16:23 -0600
                regreting not using a contraceptive (Was: Do you see the loops, in C code and in Java code? /** Looping **/) Mild Shock <janburse@fastmail.fm> - 2026-07-23 00:51 +0200
                Re: regreting not using a contraceptive (Was: Do you see the loops, in C code and in Java code? /** Looping **/) Lane W <cactus_DAC@yahoo.com> - 2026-07-22 17:13 -0600
                Re: regreting not using a contraceptive (Was: Do you see the loops, in C code and in Java code? /** Looping **/) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-22 18:23 -0700

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