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Re: Performance of hand-optimised assembly

From Stephen Sprunk <stephen@sprunk.org>
Newsgroups comp.lang.c
Subject Re: Performance of hand-optimised assembly
Date 2011-12-26 14:24 -0600
Organization A noiseless patient Spider
Message-ID <jdal5r$3n3$1@dont-email.me> (permalink)
References <0.d0ecd8f477637819bed2.20111223184332GMT.87pqffjfhn.fsf@bsb.me.uk> <jd7sjj$gum$1@speranza.aioe.org> <11940381.755.1324841772361.JavaMail.geo-discussion-forums@pruu23> <jd81e9$qs5$1@speranza.aioe.org>

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On 25-Dec-11 14:35, jacob navia wrote:
> Le 25/12/11 20:36, 88888 Dihedral a écrit :
>> If computing PI or RSA2048 encoding and decoding, nowadays the job is
>> still paid well to use 64 bit multipliers in HW directly.
> 
> Look at this:
> 
> void doADD(double *L, double *R, double *result,size_t n)
> {
>     for(size_t i=0; i<n;i++) result[i]=L[i]+R[i];
> }
> 
> Assembly will always do better than standard C in the above specific
> code. You can then use the ADDPD and add 2 integers at the same time
> (under specific loop conditions).

... unless you have a vectorizing compiler, which will do the exact same
thing for you without the need for inline assembly.  Also, when AVX
support comes out, that vectorizing compiler will start using AVX
instructions while your assembly is stuck using SSE.  Oh, and that
compiler could generate vector code for _other_ architectures as well
eg. VIS), where your assembly code would break compilation.

Furthermore, there is no guaranteed win for using SEE; early SSE chips
simply decoded that into two FADDs, so there was no performance benefit
to all that work you invested in writing SSE assembly.  (The same is
likely to be true with early AVX chips.)

S

-- 
Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking

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Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-23 18:43 +0000
  Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-23 19:40 +0000
    Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-23 21:26 +0000
      Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-23 22:02 +0000
        Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-24 02:52 +0000
          Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-23 20:32 -0800
            Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-24 13:09 +0000
              Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-24 05:49 -0800
                Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-24 15:30 +0000
                Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-24 08:15 -0800
                Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-24 17:10 +0000
                Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-24 23:25 +0000
                Re: Performance of hand-optimised assembly jgk@panix.com (Joe keane) - 2012-01-04 03:24 +0000
                Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-04 09:59 +0100
                Re: Performance of hand-optimised assembly jgk@panix.com (Joe keane) - 2012-01-04 20:57 +0000
                Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2012-01-04 23:04 +0000
                Re: Performance of hand-optimised assembly Noob <root@127.0.0.1> - 2012-01-05 13:32 +0100
              Re: Performance of hand-optimised assembly Philip Lantz <prl@canterey.us> - 2011-12-24 15:29 -0800
          Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-24 12:42 +0000
            Re: Performance of hand-optimised assembly Jens Gustedt <jens.gustedt@loria.fr> - 2011-12-24 16:58 +0100
          Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-24 13:55 +0000
            Re: Performance of hand-optimised assembly Seebs <usenet-nospam@seebs.net> - 2011-12-24 19:24 +0000
              Re: Performance of hand-optimised assembly Geoff <geoff@invalid.invalid> - 2011-12-24 13:44 -0800
            Re: Performance of hand-optimised assembly Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-12-29 02:53 +0200
              Re: Performance of hand-optimised assembly Rui Maciel <rui.maciel@gmail.com> - 2011-12-29 02:11 +0000
  Re: Performance of hand-optimised assembly jgk@panix.com (Joe keane) - 2011-12-24 01:36 +0000
  Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2011-12-24 06:44 +0100
    Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2011-12-24 09:52 +0100
    Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2011-12-26 08:05 +0100
      Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-26 11:52 -0800
        Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2011-12-27 07:28 +0100
  Re: Performance of hand-optimised assembly Willem <willem@toad.stack.nl> - 2011-12-24 12:48 +0000
    Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-24 04:56 -0800
    Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-24 23:39 +0000
  Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-24 06:01 -0800
    Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-24 14:55 +0000
      Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-28 03:46 -0800
        Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-28 04:52 -0800
    Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-25 00:07 +0000
      Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-28 03:21 -0800
        Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-28 13:19 +0000
          Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-28 16:01 +0000
            Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-28 17:45 +0000
              Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-28 18:56 -0800
            Re: Performance of hand-optimised assembly Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-12-29 03:32 +0200
            Re: Performance of hand-optimised assembly Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 17:03 -0800
              Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-26 22:08 +0000
                Re: Performance of hand-optimised assembly Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 22:20 -0800
        Re: Performance of hand-optimised assembly James Kuyper <jameskuyper@verizon.net> - 2011-12-28 08:24 -0500
        Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-28 14:27 +0000
          Re: Performance of hand-optimised assembly Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 16:50 -0800
            Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-26 21:59 +0000
        Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-28 11:12 -0800
        Re: Performance of hand-optimised assembly Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-12-29 03:12 +0200
          Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2011-12-29 10:02 +0100
            Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-29 12:06 +0000
            Re: Performance of hand-optimised assembly Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 17:07 -0800
              Re: Performance of hand-optimised assembly Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-02-13 01:18 +0200
                Re: Performance of hand-optimised assembly Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-08 10:54 -0800
          Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2011-12-29 10:02 +0100
          Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-29 12:06 +0000
            Re: Performance of hand-optimised assembly Keith Thompson <kst-u@mib.org> - 2011-12-29 11:44 -0800
            Re: Performance of hand-optimised assembly Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 17:23 -0800
          Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2011-12-29 08:37 -0800
            Re: Performance of hand-optimised assembly Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-01-05 22:19 +0200
  Re: Performance of hand-optimised assembly James Dow Allen <gmail@jamesdowallen.nospam> - 2011-12-24 16:21 +0000
    Re: Performance of hand-optimised assembly Weland <weland@otaku.freeshell.org> - 2011-12-25 10:54 +0000
  Re: Performance of hand-optimised assembly "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2011-12-24 14:52 -0800
  Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2011-12-25 20:12 +0100
    Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-25 11:36 -0800
      Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2011-12-25 21:35 +0100
        Re: Performance of hand-optimised assembly Stephen Sprunk <stephen@sprunk.org> - 2011-12-26 14:24 -0600
          Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2011-12-26 21:36 +0100
            Re: Performance of hand-optimised assembly Stephen Sprunk <stephen@sprunk.org> - 2012-01-04 11:59 -0600
              Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-04 20:22 +0100
                Re: Performance of hand-optimised assembly Dann Corbit <dcorbit@connx.com> - 2012-01-04 12:59 -0800
                Re: Performance of hand-optimised assembly James Harris <james.harris.1@googlemail.com> - 2012-01-04 15:32 -0800
                Re: Performance of hand-optimised assembly Stephen Sprunk <stephen@sprunk.org> - 2012-01-05 23:47 -0600
                Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-04 22:47 +0000
                Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-05 00:47 +0100
                Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-05 00:22 +0000
                Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-04 23:44 -0800
                Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2012-01-05 12:16 +0000
                Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2012-01-05 12:49 +0000
                Re: Performance of hand-optimised assembly jgk@panix.com (Joe keane) - 2012-01-05 21:26 +0000
                Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2012-01-07 10:32 +0100
                Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-05 00:58 +0100
                Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-05 13:39 -0800
                Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-07 02:15 -0800
                Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-10 01:07 -0800
                Re: Performance of hand-optimised assembly jgk@panix.com (Joe keane) - 2012-01-07 00:49 +0000
                Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-07 08:54 +0100
                Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-07 10:11 +0100
                Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2012-01-07 10:51 +0100
                Re: Performance of hand-optimised assembly jgk@panix.com (Joe keane) - 2012-01-07 20:09 +0000
        Re: Performance of hand-optimised assembly Stephen Sprunk <stephen@sprunk.org> - 2012-01-06 23:39 -0600
          Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2012-01-07 10:33 +0100
            Re: Performance of hand-optimised assembly Stephen Sprunk <stephen@sprunk.org> - 2012-01-07 07:36 -0600
              Re: Performance of hand-optimised assembly Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-07 21:03 +0000
                Re: Performance of hand-optimised assembly Stephen Sprunk <stephen@sprunk.org> - 2012-01-07 16:42 -0600
    Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-25 20:23 +0000
      Re: Performance of hand-optimised assembly jacob navia <jacob@spamsink.net> - 2011-12-25 21:50 +0100
        Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-25 22:10 +0000
      Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-25 13:11 -0800
        Re: Performance of hand-optimised assembly "BartC" <bc@freeuk.com> - 2011-12-25 22:07 +0000
          Re: Performance of hand-optimised assembly 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-25 16:39 -0800
  Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2011-12-26 05:55 +0100
    Re: Performance of hand-optimised assembly "io_x" <a@b.c.invalid> - 2012-02-17 17:58 +0100
  Re: Performance of hand-optimised assembly "Wolfgang.Draxinger" <Wolfgang.Draxinger@physik.uni-muenchen.de> - 2012-01-10 18:00 +0100

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