Do you see the loops, in C code and in Java code? / Looping / (Was: Because of MIMD you have to reassess algorithms)

From	Mild Shock <janburse@fastmail.fm>
Newsgroups	sci.logic, comp.lang.prolog, sci.physics
Subject	Do you see the loops, in C code and in Java code? / Looping / (Was: Because of MIMD you have to reassess algorithms)
Date	2026-07-23 00:09 +0200
Message-ID	<113rf37$846i$1@solani.org> (permalink)
References	(4 earlier) <113m6l8$561a$2@solani.org> <113mco7$1j9n2$1@dont-email.me> <113n4m3$5oih$1@solani.org> <113n5j3$5ouq$3@solani.org> <113r9gn$396f7$4@dont-email.me>

Cross-posted to 3 groups.

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Hi,

CAS and XADD have no looping, they
are atomic operations, that take some
time but basically have some outcome

with some ACID property and a result
value. What loops is the ADT, the Abstract
Data Type that you implement. Respectively

the client that uses the Abstract Data Type.
In your case you added the loop inside the
Abstract Data Type or lower level aggregate

code of a higher level operation:

Chris M. Thomasson wrote:
void producer(double state) {
     uint32_t ver = XADD(&head, 1);
     cell& c = cells[ver & (N - 1)];
     while (LOAD(&c.ver) != ver) backoff(); /** Looping **/
     c.state = state;
     STORE(&c.ver, ver + 1);
}
https://groups.google.com/g/lock-free/c/acjQ3-89abE/m/a6-Di0GZsyEJ

In my case I added the loop during the client
usage of the ADT:

From: Mild Shock <janburse@fastmail.fm>
Subject: Source of the benchmark for DmitryVyukov
Date: Tue, 21 Jul 2026 01:44:21 +0200

     private static void producer(Queue q) {
         for (int i = 0; i < WORK; i++) {
             Integer val = Integer.valueOf(i);
             while (!enqueue(q, val)) ; /** Looping **/
         }
     }

Do you see the two loops, in your C code
and in my Java code? They are marked with a
comment /** Looping **/ .

You see them, don't you? But I don't know
exactly what backoff() does. Sometimes loops
are spurious yield loops, required because

an ADT cannot gurantee that every yield
implies a certain condition. This is for
example already found in the intrinsinc

monitor of Java, the wait(). You might consult
Doug Lea about the matter and how idiomatic
Java code looks like dealing with

spurious yields.

Bye

Chris M. Thomasson schrieb:
> On 7/21/2026 12:02 AM, Mild Shock wrote:
>> Hi,
>>
>> Because of MIMD you have to reassess algorithms.
>> A spin loop which could really hurt non-MIMD
>> GPUs, might less hurt a MIMD GPU.
> [...]
> 
> Huh? atomic fetch-add has no looping. compare LOCK CMPXCHG with LOCK 
> XADD on x86.
>

Thread

I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM] (Re: 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
  Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov (Re: I'm a spinner, I'm a sinner [Dmitry Vyukov for pi-WAM]) Mild Shock <janburse@fastmail.fm> - 2026-07-20 08:33 +0200
    The Cache Identity Crisis by Micro Penis (Re: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov) Mild Shock <janburse@fastmail.fm> - 2026-07-20 13:54 +0200
      Just RTFM the RDNA 3.5 specs! [GPU Cache Lines] (Re: The Cache Identity Crisis by Micro Penis) Mild Shock <janburse@fastmail.fm> - 2026-07-20 14:10 +0200
        The large memory tax: ECC RAM (Re: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines]) Mild Shock <janburse@fastmail.fm> - 2026-07-20 14:23 +0200
        Re: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines] (Re: The Cache Identity Crisis by Micro Penis) Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-20 12:26 -0700
          Re: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines] (Re: The Cache Identity Crisis by Micro Penis) R Kym Horsell <kymhorsell@gmail.com> - 2026-07-20 22:20 +0000
            Friendly Reminder: GPU 10x more performant than CPU (Was: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines]) Mild Shock <janburse@fastmail.fm> - 2026-07-21 00:39 +0200
              Breaking the CUDA edge in AI by WebGPU (Was: Friendly Reminder: GPU 10x more performant than CPU) Mild Shock <janburse@fastmail.fm> - 2026-07-21 00:56 +0200
                Like WebAssembly before it, WebGPU has "escaped" the browser. (Was: Breaking the CUDA edge in AI by WebGPU) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:05 +0200
                If you are paranoid you can use Falco [Agentic AI] (Re: Like WebAssembly before it, WebGPU has "escaped" the browser.) Mild Shock <janburse@fastmail.fm> - 2026-07-21 22:57 +0200
                What would an EMACS guru say [Windows Recall] (Re: If you are paranoid you can use Falco [Agentic AI]) Mild Shock <janburse@fastmail.fm> - 2026-07-21 23:35 +0200
                Decide what you critique tiny winy penis (Re: What would an EMACS guru say [Windows Recall]) Mild Shock <janburse@fastmail.fm> - 2026-07-22 08:17 +0200
                How confused is tiny winy penis? (Was: Decide what you critique tiny winy penis) Mild Shock <janburse@fastmail.fm> - 2026-07-22 08:28 +0200
                Maybe change your hobby, become a dog owner? (Was: How confused is tiny winy penis?) Mild Shock <janburse@fastmail.fm> - 2026-07-22 09:37 +0200
                Even dogs know Switzerland != Germany [Syphilis Brain Micro Penis] (Re: Decide what you critique tiny winy penis ) Mild Shock <janburse@fastmail.fm> - 2026-07-22 11:19 +0200
                node.js has also Worker isolation , headless (Was: Even dogs know Switzerland != Germany [Syphilis Brain Micro Penis]) Mild Shock <janburse@fastmail.fm> - 2026-07-22 11:29 +0200
                Abyss hobby interpretation vs. professional understanding [Keep up with the Kardashians] (Re: node.js has also Worker isolation , headless) Mild Shock <janburse@fastmail.fm> - 2026-07-22 11:38 +0200
                Play stupid games, win classic Usenet prizes [CCCP Troll] (Re: Abyss hobby interpretation vs. professional understanding [Keep up with the Kardashians]) Mild Shock <janburse@fastmail.fm> - 2026-07-22 12:16 +0200
                Glue Sniffing 5-Year Old Moron [CCCP Troll] (Was: Play stupid games, win classic Usenet prizes [CCCP Troll]) Mild Shock <janburse@fastmail.fm> - 2026-07-22 14:29 +0200
                My Swift Go 16 AI has no IMEI, are you nuts? (Re: Even dogs know Switzerland != Germany [Syphilis Brain Micro Penis]) Mild Shock <janburse@fastmail.fm> - 2026-07-22 14:15 +0200
                Same nickname and email, could post faster [5 year old moron] (Re: My Swift Go 16 AI has no IMEI, are you nuts? ) Mild Shock <janburse@fastmail.fm> - 2026-07-22 14:25 +0200
                I have nothing to hide, you can find me in search.ch (Re: My Swift Go 16 AI has no IMEI, are you nuts?) Mild Shock <janburse@fastmail.fm> - 2026-07-22 14:41 +0200
                Where did I confirm German via .ch, you are more than nuts! (Re: I have nothing to hide, you can find me in search.ch) Mild Shock <janburse@fastmail.fm> - 2026-07-22 14:48 +0200
                Ask a Ukrainian Neighbour to do Detective [CCCP Troll] (Re: Where did I confirm German via .ch, you are more than nuts! ) Mild Shock <janburse@fastmail.fm> - 2026-07-22 14:51 +0200
          Re: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines] (Re: The Cache Identity Crisis by Micro Penis) Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-20 21:36 -0700
            rossy boy is going paranoid (Was: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines]) Mild Shock <janburse@fastmail.fm> - 2026-07-21 09:01 +0200
              Re: rossy boy is going paranoid (Was: Just RTFM the RDNA 3.5 specs! [GPU Cache Lines]) Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-07-21 00:56 -0700
      L1,..,Ln caches are located on the CPU AND on the GPU (Was: The Cache Identity Crisis by Micro Penis( Mild Shock <janburse@fastmail.fm> - 2026-07-20 19:35 +0200
        GPU Cache Hierarchy: Understanding L1, L2, and VRAM (Was: L1,..,Ln caches are located on the CPU AND on the GPU) Mild Shock <janburse@fastmail.fm> - 2026-07-20 19:40 +0200
          Well thats good, co-location, onto the same processor die (Re: GPU Cache Hierarchy: Understanding L1, L2, and VRAM (Was: L1,..,Ln caches are located on the CPU AND on the GPU) Mild Shock <janburse@fastmail.fm> - 2026-07-20 22:02 +0200
            Where is micro penis mental error? (Re: Well thats good, co-location, onto the same processor die (Re: GPU Cache Hierarchy: Understanding L1, L2, and VRAM (Was: L1,..,Ln caches are located on the CPU AND on the GPU) Mild Shock <janburse@fastmail.fm> - 2026-07-20 22:07 +0200
    I didn't find Futex in WebGPU / WGSL (Re: Gemini, DeepSeek, OpenAI all know Dmitriy V'jukov) Mild Shock <janburse@fastmail.fm> - 2026-07-20 23:26 +0200
      There is no imageAtomicAdd in WGSL (Re: I didn't find Futex in WebGPU / WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 00:15 +0200
        OpenGL is dead. Apple said bye bye / Wayland Compositor (Re: There is no imageAtomicAdd in WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 00:26 +0200
        Flogging a Dead Horse, OpenGL is EOL (Re: There is no imageAtomicAdd in WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:39 +0200
          imageAtomicAdd trivial, Dmitry Vyukov requires capacity (Re: Flogging a Dead Horse, OpenGL is EOL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:40 +0200
            capacity = 2^n for some n / systolic system (Re: imageAtomicAdd trivial, Dmitry Vyukov requires capacity) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:41 +0200
              Source of the benchmark for DmitryVyukov (Was: capacity = 2^n for some n / systolic system) Mild Shock <janburse@fastmail.fm> - 2026-07-21 01:44 +0200
        Re: There is no imageAtomicAdd in WGSL (Re: I didn't find Futex in WebGPU / WGSL) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-20 16:59 -0700
          I never used OpenGL Version 4.2 and later (Was: There is no imageAtomicAdd in WGSL) Mild Shock <janburse@fastmail.fm> - 2026-07-21 08:47 +0200
            Because of MIMD you have to reassess algorithms (Re: I never used OpenGL Version 4.2 and later) Mild Shock <janburse@fastmail.fm> - 2026-07-21 09:02 +0200
              Re: Because of MIMD you have to reassess algorithms (Re: I never used OpenGL Version 4.2 and later) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-22 13:34 -0700
                Do you see the loops, in C code and in Java code? /** Looping **/ (Was: Because of MIMD you have to reassess algorithms) Mild Shock <janburse@fastmail.fm> - 2026-07-23 00:09 +0200
                Re: Do you see the loops, in C code and in Java code? /** Looping **/ (Was: Because of MIMD you have to reassess algorithms) Mild Shock <janburse@fastmail.fm> - 2026-07-23 00:53 +0200
                Re: Do you see the loops, in C code and in Java code? /** Looping **/ (Was: Because of MIMD you have to reassess algorithms) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-22 18:00 -0700
                Re: Do you see the loops, in C code and in Java code? /** Looping **/ (Was: Because of MIMD you have to reassess algorithms) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-07-22 18:20 -0700
                Why do you even need a mpmc queue? [Thunder Kittens] (Was: Do you see the loops, in C code and in Java code? /** Looping **/) Mild Shock <janburse@fastmail.fm> - 2026-07-24 14:44 +0200
                What does pi in pi-WAM mean? (Re: Why do you even need a mpmc queue? [Thunder Kittens]) Mild Shock <janburse@fastmail.fm> - 2026-07-24 14:53 +0200
                OR-parallelism or AND-parallelism? [MapReduce] (Was: What does pi in pi-WAM mean?) Mild Shock <janburse@fastmail.fm> - 2026-07-24 15:00 +0200
                It is all on GitHub , for the 100-th time! (Re: What does pi in pi-WAM mean?) Mild Shock <janburse@fastmail.fm> - 2026-07-24 20:13 +0200

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