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Re: A useless machine

From Michael S <already5chosen@yahoo.com>
Newsgroups comp.arch
Subject Re: A useless machine
Date 2026-02-16 18:31 +0200
Organization A noiseless patient Spider
Message-ID <20260216183146.00007902@yahoo.com> (permalink)
References <10mpgtp$32h0n$1@dont-email.me> <10mvecq$10h03$1@dont-email.me>

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On Mon, 16 Feb 2026 07:50:49 -0800
Stephen Fuld <sfuld@alumni.cmu.edu.invalid> wrote:

> On 2/14/2026 1:57 AM, Thomas Koenig wrote:
> > Some people are throwing large amounts of computing power at trying
> > to disprove the Collatz conjecture.  Graphics cards have sped this
> > up enormously.  
> 
> big snip
> 
> > 
> > The number of iterations would be tracked; if larger than a prevous
> > record, the calculation would terminate with a corresponding signal
> > to the outside world.
> > 
> > Also, each cycle, the result from the previous round would be
> > compared against the input value.  If it is lower, the next number
> > would be chosen.  Finally, the number reached would be checked
> > against the previous, pre-set maximum, with would also signal to
> > the outside world.  
> 
> Hold these thoughts
> 
> snip
> 
> > The problem is embarassingly parallel.   
> 
> 
> Sort of.  You could do it that way, but you would be giving up some 
> performance.  Specifically, as you say, you want to check the number 
> against the previous input value and the preset maximum.  But in a 
> parallel implementation, you want to check against the largest value 
> checked *across all the parallel threads*.  In order to do that, the 
> threads need to communicate, thus violating the "embarrassingly 
> parallel" rule.  I don't know how much performance you would give up
> so it may not make much difference,

If initial values N0 are above 2**64 and the number of tests NP that run
in parallel is few millions or even few hundreds of millions then
performance gain achieved by comparison vs N0+NP instead of comparison
vs N0 is negligible.

> nor do I know the cost of keeping
> some "global" largest value checked so far.  There is a tradeoff here.
>

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A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-14 09:57 +0000
  Re: A useless machine MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-14 18:48 +0000
    Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-14 20:18 +0100
      Re: A useless machine MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-14 21:22 +0000
        Re: A useless machine Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-02-14 13:30 -0800
        Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-15 12:50 +0100
          Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-21 13:48 -0600
            Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-21 21:40 +0100
              Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-21 15:17 -0600
                Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-22 04:50 -0600
              Re: A useless machine Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-12 21:01 -0700
            Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-22 14:43 +0100
              Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-22 12:38 -0600
                Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-23 10:51 +0100
                Re: A useless machine MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-26 01:27 +0000
                Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-26 09:21 +0100
                Re: A useless machine Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-12 21:11 -0700
      Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-15 14:58 +0100
      Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-21 12:27 -0600
        Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-22 15:14 +0100
      Re: A useless machine Stefan Monnier <monnier@iro.umontreal.ca> - 2026-02-22 11:41 -0500
        Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-23 10:53 +0100
          Re: A useless machine Stefan Monnier <monnier@iro.umontreal.ca> - 2026-02-23 10:52 -0500
  Re: A useless machine Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-02-14 21:19 -0800
  Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-15 03:58 -0500
    Re: A useless machine David Brown <david.brown@hesbynett.no> - 2026-02-15 13:14 +0100
      Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-15 15:46 +0000
      Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-15 10:56 -0500
        Re: A useless machine MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-15 19:16 +0000
          Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-15 22:40 +0100
            Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-26 19:31 +0000
        Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-18 18:22 +0200
          Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-18 22:56 -0500
            Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-19 12:10 +0200
              Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-21 01:56 -0500
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-21 19:23 +0200
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-21 20:36 +0200
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-22 10:46 +0200
                Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-22 12:45 +0100
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-22 16:35 +0200
                Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-22 19:12 -0500
                Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-22 19:47 -0500
                Re: A useless machine EricP <ThatWouldBeTelling@thevillage.com> - 2026-02-21 15:39 -0500
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-22 03:16 +0200
                Re: A useless machine EricP <ThatWouldBeTelling@thevillage.com> - 2026-02-22 14:48 -0500
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-22 23:25 +0200
            Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-19 11:51 +0100
              Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-19 23:12 +0200
                Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-20 15:11 +0100
            Re: A useless machine Stefan Monnier <monnier@iro.umontreal.ca> - 2026-02-19 15:27 -0500
              Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-20 11:41 +0200
              Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-22 18:41 -0600
                Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-23 11:10 +0000
                Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-23 17:24 -0600
                Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-24 06:44 +0000
                Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-24 01:38 -0600
                Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-24 03:16 -0600
                Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-24 04:52 -0600
                Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-24 11:16 +0000
                Re: A useless machine BGB <cr88192@gmail.com> - 2026-02-24 13:19 -0600
                Re: A useless machine Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-12 21:14 -0700
          Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-20 08:01 +0000
    Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-15 15:35 +0200
      Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-15 18:33 +0200
        Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-15 19:19 +0000
          Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-16 12:31 +0200
            Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-17 15:41 +0200
              Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-17 18:17 +0200
    Re: A useless machine anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-02-15 22:41 +0000
  Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-15 14:52 +0100
    Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-15 16:45 +0000
      Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-15 18:01 +0100
        Re: A useless machine Thomas Koenig <tkoenig@netcologne.de> - 2026-02-15 19:42 +0000
          Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-15 22:59 +0100
            Re: A useless machine Robert Finch <robfi680@gmail.com> - 2026-02-15 21:53 -0500
              Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-16 12:40 +0200
                Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-16 20:34 +0200
              Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-16 16:08 +0100
  Re: A useless machine Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-02-16 07:50 -0800
    Re: A useless machine Michael S <already5chosen@yahoo.com> - 2026-02-16 18:31 +0200
    Re: A useless machine Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-18 21:56 +0100

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