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Re: Wish to try Linux

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On 06/02/2013 04:33 AM, Richard Kettlewell wrote:
> Jean-David Beyer <jeandavid8@verizon.net> writes:
>> In the distant past, a colleague and I had occasion to write an
>> assembly-language level optimizer (mainly for C programs) for the SPARC
>> RISC processor. We had already done one for the AT&T 32100 series
>> processors (conventional architecture). I found doing that to be
>> somewhat more difficult than for the normal processors such as Intel
>> 80386 and the Motorola 68000 series of the same time. Delay slots, etc.
>>
>> But I did not find that they used any less memory for the instructions
>> because any one instruction may have been smaller than for complex
>> instruction set machines, but it took between 2 or 3 instructions to
>> do the same thing as a single instruction on the more traditional
>> machines.  Furthermore, you then had to do 2 to 3 instruction fetches,
>> so they tended to run slower per computation even though any single
>> instruction could run faster.
> 
> Comparing a few libraries which we build across multiple platforms, I
> find SPARC produces object code up to 1-50% bigger than x86, but x86
> 20-30% bigger than PPC.  My conclusion is that you can’t reliably say
> RISC ISAs produce either larger or smaller code than CISC, and aren’t on
> particularly solid ground seeking a comparison just between two specific
> ISAs - i.e. it can vary a fair bit depending on the specific code.
> 
> (Stripped object code in all cases, mostly compiled C.)
> 
My guess is that you are right. Where I worked, they also were trying to
build a processor RISC chip oriented specifically to running compiled C
programs. I do not know if they ever manufactured the chip or not, but I
did get a copy of the instruction set. I do not know what they were
anymore, but I do remember that this so-called RISC processor, that they
were calling CRISP at the time, had more op-codes than any other machine
I had ever seen, even the IBM 7094, Something like 350 op-codes. I was
disgusted. If that is C REDUCED INSTRUCTION SET PROCESSOR, I do not know
what they thought would be a complex instruction set machine. I know I
never got asked to write an optimizer for it.

That company, that once was a pioneer in computers, had completely lost
it, technically, by the time they were allowed to make computers again.
They had designed a pretty good 32-bit processor when people were trying
to make do with a PDP-11 computer or an 8086 Intel chip. We did the
optimizer for it. They had a bunch of benchmarks that we were to
optimize for, and they were very stupid. We could easily get 10:1 speed
ups on then. They even had a C version of the so-called Whetstone
benchmark. But their version had some errors in it. Our optimizer made
that go so fast it was difficult to time it. There was one loop in there
that added or multiplied a bunch of floating point numbers and did it
10,000 times (or something like that). I had put a loop invariant code
motion optimization in there, and it moved all the calculations outside
the loop for a fantastic speed-up. My colleague had live-dead analysis
and noticed that the empty loop had nothing in it, and that the loop
variable was not used later, so he removed those instructions. He also
removed the instructions I had moved out of the loop, since their values
were never used. That happened to most of the code in that so-called
benchmark.

We later did a study of the programs actually used by the UNIX machines
in our computation center. We found out what the most-used programs were
and made benchmarks from them. The troff (text processor) program was
the winner and we made a benchmark from it. But marketing would not let
us use it because it got only 1% (or something like that) improvement.
Programming style at that company was terrible from an optimization
standpoint. The programmers, who were mostly researchers and never wrote
for production, were terrible. They loved to make all variables external
(in C), to save the bother of passing arguments to functions. But
optimizing code with external variables was almost impossible because
those variables could appear in other files that the optimizer could not
see, so we had no way of knowing if code in another file could change
their values unseen to us, so we could not optimize them.

But some genius in marketing said there was a multiply of a floating
point number by two, and they designed a multiply by 2 floating point
op-code for it (that added 1 to the exponent). I told them not to do it
because we would never generate the instruction because that "2" was an
external variable and it could change, unseen by the program, if an
interrupt came along. So they put it in anyway and we never generated
it. I said that they would have been wiser to use the chip area to
increase the size of the instruction cache (from 2 instructions to some
more), but they did not do it. They were in love with useless complexity.

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Thread

Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-09 20:09 +0100
  Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-09 15:25 -0400
    Re: Wish to try Linux Robert Heller <heller@deepsoft.com> - 2013-05-09 15:24 -0500
      Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-09 21:51 +0100
      Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-09 18:41 -0400
  Re: Wish to try Linux Dan Espen <despen@verizon.net> - 2013-05-09 15:28 -0400
    Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-10 16:48 +0100
  Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-09 20:48 +0100
    Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-09 16:45 -0400
      Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-09 23:50 +0100
        Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-10 07:41 -0400
          Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 13:01 +0100
            Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-10 08:49 -0400
              Re: Wish to try Linux Aragorn <stryder@telenet.be.invalid> - 2013-05-10 15:20 +0200
                Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-10 16:11 -0400
          Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-10 08:04 -0400
            Re: Wish to try Linux Bill Marcum <bill@nowhere.invalid> - 2013-05-16 07:58 -0400
          Re: Wish to try Linux Bill Marcum <bill@nowhere.invalid> - 2013-05-16 07:56 -0400
            Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-16 09:32 -0400
              Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-05-16 16:03 +0200
                Re: Wish to try Linux John Hasler <jhasler@newsguy.com> - 2013-05-16 09:27 -0500
                Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-16 10:53 -0400
                Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-16 15:30 +0100
                Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-16 10:52 -0400
              Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-16 15:30 +0100
              Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-16 16:14 -0400
                Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-16 17:23 -0400
    Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-05-09 23:49 +0000
      Re: Wish to try Linux Robert Heller <heller@deepsoft.com> - 2013-05-09 19:35 -0500
        Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 05:30 +0100
          Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-05-10 14:27 +0000
      Re: Wish to try Linux Michael Black <et472@ncf.ca> - 2013-05-09 22:13 -0400
    Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-10 16:50 +0100
      Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 17:19 +0100
        Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-15 16:27 +0100
          Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-15 16:34 +0000
            Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-15 17:46 +0100
              Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-15 18:15 +0000
                Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-15 19:32 +0100
                Re: Wish to try Linux Dan Espen <despen@verizon.net> - 2013-05-15 14:52 -0400
                Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-15 21:11 +0000
                Re: Wish to try Linux Robert Heller <heller@deepsoft.com> - 2013-05-15 13:54 -0500
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-16 01:01 -0400
                Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-05-16 10:52 +0200
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-16 08:25 -0400
                Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-16 18:56 +0000
                Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-16 20:33 +0100
                Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-16 19:35 +0000
                Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-16 20:43 +0100
                Re: Wish to try Linux bruce.sinclair@NOSPAMORELSEagresearch.NOTco.NOTnz (Bruce Sinclair) - 2013-05-19 23:33 +0000
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-16 16:16 -0400
          Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-15 17:44 +0100
            Re: Wish to try Linux Robert Heller <heller@deepsoft.com> - 2013-05-15 13:44 -0500
              Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-15 20:37 +0100
    Re: Wish to try Linux "Chris F.A. Johnson" <cfajohnson@gmail.com> - 2013-05-14 13:51 -0400
      Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-14 21:16 +0100
        Re: Wish to try Linux "Chris F.A. Johnson" <cfajohnson@gmail.com> - 2013-05-14 17:49 -0400
          Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-15 00:02 +0100
  Re: Wish to try Linux Robert Heller <heller@deepsoft.com> - 2013-05-09 15:03 -0500
    Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-23 14:09 +0100
      Re: Wish to try Linux Richard Kettlewell <rjk@greenend.org.uk> - 2013-05-23 14:38 +0100
        Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-23 16:33 +0100
          Re: Wish to try Linux John Hasler <jhasler@newsguy.com> - 2013-05-23 10:55 -0500
            Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-23 19:00 +0100
              Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-06-01 11:43 +0200
                Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-06-01 11:37 +0000
                Re: Wish to try Linux Balwinder S Dheeman <bsd.SANSPAM@anu.homelinux.net> - 2013-06-01 21:59 +0530
                Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-06-01 19:14 +0200
                Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-06-01 17:43 +0000
                Re: Wish to try Linux Michael Black <et472@ncf.ca> - 2013-06-01 19:33 -0400
                Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-06-02 02:37 +0200
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-06-01 23:05 -0400
                Re: Wish to try Linux Richard Kettlewell <rjk@greenend.org.uk> - 2013-06-02 09:33 +0100
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-06-02 07:02 -0400
                Re: Wish to try Linux David Brown <david.brown@removethis.hesbynett.no> - 2013-06-02 13:26 +0200
                Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-06-02 15:47 +0100
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-06-02 14:52 -0400
                Re: Wish to try Linux David Brown <david.brown@removethis.hesbynett.no> - 2013-06-02 13:32 +0200
          Re: Wish to try Linux Roger Blake <rogblake@iname.invalid> - 2013-05-23 17:09 +0000
            Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-23 19:06 +0100
            Re: Wish to try Linux Robert Riches <spamtrap42@jacob21819.net> - 2013-05-24 04:48 +0000
  Re: Wish to try Linux Bit Twister <BitTwister@mouse-potato.com> - 2013-05-09 20:03 +0000
  Re: Wish to try Linux unruh <unruh@invalid.ca> - 2013-05-09 20:19 +0000
    Re: Wish to try Linux bad sector <forgetski@postit_INVALID_.gov> - 2013-05-09 20:27 -0400
      Re: Wish to try Linux unruh <unruh@invalid.ca> - 2013-05-10 15:30 +0000
  Re: Wish to try Linux Stef <not@this.address.com> - 2013-05-10 03:05 +0000
    Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-05-10 14:35 +0000
      Re: Wish to try Linux Stef <not@this.address.com> - 2013-05-10 16:44 +0000
        Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-05-10 16:57 +0000
          Re: Wish to try Linux Stef <not@this.address.com> - 2013-05-11 03:59 +0000
            Re: Wish to try Linux Michael Black <et472@ncf.ca> - 2013-05-11 00:27 -0400
              Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-05-11 12:49 +0000
                Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-11 12:56 +0000
                Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-05-11 15:20 +0200
                Re: Wish to try Linux notbob <notbob@nothome.com> - 2013-05-11 14:14 +0000
                Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-11 10:30 -0400
                Re: Wish to try Linux  OOps Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-11 10:38 -0400
                Re: Wish to try Linux  OOps Robert Riches <spamtrap42@jacob21819.net> - 2013-05-12 04:37 +0000
                Re: Wish to try Linux Michael Black <et472@ncf.ca> - 2013-05-11 13:47 -0400
    Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-10 16:58 +0100
  Re: Wish to try Linux Aragorn <stryder@telenet.be.invalid> - 2013-05-10 06:53 +0200
    Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 07:26 +0100
      Re: Wish to try Linux Aragorn <stryder@telenet.be.invalid> - 2013-05-10 09:18 +0200
        Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 10:20 +0100
          Re: Wish to try Linux Aragorn <stryder@telenet.be.invalid> - 2013-05-10 11:40 +0200
      Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-10 07:44 -0400
        Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 13:00 +0100
          Re: Wish to try Linux Octothorpe <Octothorpe@invalid.com> - 2013-05-10 08:47 -0400
            Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 15:50 +0100
    Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-21 18:44 +0100
      Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-06-21 19:53 +0200
        Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-21 18:55 +0100
          Re: Wish to try Linux Aragorn <thorongil@telenet.be.invalid> - 2013-06-21 20:05 +0200
      Re: Wish to try Linux Richard Kettlewell <rjk@greenend.org.uk> - 2013-06-21 19:17 +0100
        Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-21 19:56 +0100
          Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-21 19:59 +0100
      Re: Wish to try Linux Antti Talsta <atalsta@gmail.com> - 2013-06-21 21:04 +0300
      Re: Wish to try Linux Michael Black <et472@ncf.ca> - 2013-06-21 17:51 -0400
      Re: Wish to try Linux Roger Blake <rogblake@iname.invalid> - 2013-06-22 01:48 +0000
      Re: Wish to try Linux Stan Bischof <stan@worldbadminton.com> - 2013-06-24 16:48 +0000
      Re: Wish to try Linux Stan Bischof <stan@worldbadminton.com> - 2013-06-24 16:56 +0000
  Re: Wish to try Linux DenverD <DenverD@invalid.dk> - 2013-05-10 09:17 +0200
  Re: Wish to try Linux lichtblitz <nospam@lichtblitz.invalid> - 2013-05-10 13:49 +0000
    Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-05-10 15:48 +0100
      Re: Wish to try Linux Robert Heller <heller@deepsoft.com> - 2013-05-10 11:21 -0500
        Re: Wish to try Linux lichtblitz <nospam@lichtblitz.invalid> - 2013-05-10 18:20 +0000
          Re: Wish to try Linux Richard Kettlewell <rjk@greenend.org.uk> - 2013-05-10 19:54 +0100
          Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-10 14:55 -0400
          Re: Wish to try Linux Aragorn <stryder@telenet.be.invalid> - 2013-05-11 05:40 +0200
            Re: Wish to try Linux Jean-David Beyer <jeandavid8@verizon.net> - 2013-05-11 07:55 -0400
    Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-10 16:07 +0000
      Re: Wish to try Linux lichtblitz <nospam@lichtblitz.invalid> - 2013-05-10 18:29 +0000
        Re: Wish to try Linux J G Miller <miller@yoyo.ORG> - 2013-05-10 19:48 +0000
  Re: Wish to try Linux David Hough <noone$$@llondel.org> - 2013-05-10 18:13 +0100
  Re: Wish to try Linux Dirk Weber <dma-weber@globe.lu> - 2013-05-10 19:09 +0200
  Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-05-14 19:01 +0100
    Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-23 22:55 +0100
      Re: Wish to try Linux The Natural Philosopher <tnp@invalid.invalid> - 2013-06-24 00:34 +0100
        Re: Wish to try Linux John Hasler <jhasler@newsguy.com> - 2013-06-23 19:23 -0500
          Re: Wish to try Linux David Brown <david.brown@removethis.hesbynett.no> - 2013-06-25 18:50 +0200
      Re: Wish to try Linux bruce.sinclair@NOSPAMORELSEagresearch.NOTco.NOTnz (Bruce Sinclair) - 2013-06-23 22:53 +0000
        Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-25 12:24 +0100
          Re: Wish to try Linux Michael Black <et472@ncf.ca> - 2013-06-25 12:28 -0400
          Re: Wish to try Linux bruce.sinclair@NOSPAMORELSEagresearch.NOTco.NOTnz (Bruce Sinclair) - 2013-06-25 23:11 +0000
      Re: Wish to try Linux John Hasler <jhasler@newsguy.com> - 2013-06-23 19:30 -0500
        Re: Wish to try Linux Ross Maloney <rmatycorp@iinet.net.au> - 2013-06-24 11:07 +0800
        Re: Wish to try Linux Peter Percival <peterxpercival@hotmail.com> - 2013-06-25 12:52 +0100

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