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Re: SIMD Considered Harmful

From MitchAlsup <user5857@newsgrouper.org.invalid>
Newsgroups comp.arch
Subject Re: SIMD Considered Harmful
References <1790208006-5857@newsgrouper.org> <11920i6$29ujm$3@dont-email.me>
Date 2026-09-24 17:09 +0000
Message-ID <1790269788-5857@newsgrouper.org> (permalink)

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Lawrence =?iso-8859-13?q?D=FFOliveiro?= <ldo@nz.invalid> posted:

> On Thu, 24 Sep 2026 00:00:06 GMT, MitchAlsup wrote:
> 
> > The old paper
> > https://www.sigarch.org/simd-instructions-considered-harmful/
> > compares SIMD implementations with Vector implementations--as-if
> > they were the only 2 games in town. ...
> >
> > and goes on to extoll the beneficial properties of Vectors over SIMD
> > using RISC-V as exemplary. Let me pivot the conversation back to My
> > 66000 virtual-Vector-Method vVM (an alternative to both SIMD and
> > Vectors).
> 
> Would you agree, though, that SIMD is the least attractive of the
> three approaches?

On instruction addition, yes; however SIMD is generally better at
superluminal execution--1 SIMD instruction outside of any looping 
behavior. 

SIMD has arguably better cache characteristics, but for really 
large vectors, both are cache killers. My 66000 vectors have
the ability to bypass the cache (LD/ST miss) to avoid strip-
mining of cache data by use-once data.

Cray-vectors are arguably better at instruction addition than SIMD
and arguably inefficient when the element count of the vector 
is small (4).

At one point in my architectural career, I was a fan of vectors
(1980-1995-ish); at another I was a fan of SIMD (2000-2015),
but both fell out of favor when I finally saw the damage they do
to instruction sets. That was the genesis of vVM.

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Thread

SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-24 00:00 +0000
  Re: SIMD Considered Harmful Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-09-24 02:05 +0000
    Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-24 17:09 +0000
      Re: SIMD Considered Harmful Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-09-25 00:08 +0000
        Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-25 00:41 +0000
          Re: SIMD Considered Harmful Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-09-25 22:13 +0000
            Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-26 00:29 +0000
              Re: SIMD Considered Harmful anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-09-26 06:41 +0000
                Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-26 18:23 +0000
                Re: SIMD Considered Harmful BGB <cr88192@gmail.com> - 2026-09-26 14:47 -0500
                Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-26 21:31 +0000
                Re: SIMD Considered Harmful BGB <cr88192@gmail.com> - 2026-09-26 20:56 -0500
                Re: SIMD Considered Harmful scott@slp53.sl.home (Scott Lurndal) - 2026-09-28 15:29 +0000
                Re: SIMD Considered Harmful BGB <cr88192@gmail.com> - 2026-09-28 17:39 -0500
                Re: SIMD Considered Harmful scott@slp53.sl.home (Scott Lurndal) - 2026-09-29 00:09 +0000
                Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-13 21:40 +0000
                Re: SIMD Considered Harmful Torbjorn Lindgren <tl@none.invalid> - 2026-09-29 17:01 +0000
                Re: SIMD Considered Harmful BGB <cr88192@gmail.com> - 2026-09-29 20:49 -0500
    Re: SIMD Considered Harmful BGB <cr88192@gmail.com> - 2026-09-24 15:04 -0500
  Re: SIMD Considered Harmful Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-09-24 07:54 -0700
    Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-24 19:48 +0000
      Re: SIMD Considered Harmful Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-09-24 13:58 -0700
        Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-24 22:24 +0000
          Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-25 00:27 +0000
          Re: SIMD Considered Harmful EricP <ThatWouldBeTelling@thevillage.com> - 2026-09-25 17:44 -0400
            Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-25 23:03 +0000
              Re: SIMD Considered Harmful EricP <ThatWouldBeTelling@thevillage.com> - 2026-09-27 11:33 -0400
                Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-28 00:04 +0000
                Re: SIMD Considered Harmful EricP <ThatWouldBeTelling@thevillage.com> - 2026-09-29 12:17 -0400
  Re: SIMD Considered Harmful Thomas Koenig <tkoenig@netcologne.de> - 2026-09-26 11:26 +0000
    Re: SIMD Considered Harmful Terje Mathisen <terje.mathisen@tmsw.no> - 2026-09-26 17:57 +0200
    Re: SIMD Considered Harmful BGB <cr88192@gmail.com> - 2026-09-26 13:52 -0500
      Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-26 21:24 +0000
    Re: SIMD Considered Harmful MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-26 21:16 +0000
  Re: SIMD Considered Harmful aph@littlepinkcloud.invalid - 2026-09-28 09:53 +0000

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