Re: use of pointers

From	yatremblay@bel1lin202.(none) (Yannick Tremblay)
Newsgroups	comp.lang.c++
Subject	Re: use of pointers
Date	2012-03-08 10:08 +0000
Organization	A noiseless patient Spider
Message-ID	<jja0ep$ckb$1@dont-email.me> (permalink)
References	<0ea866f3-d443-4014-93fe-507d76ee6528@em9g2000vbb.googlegroups.com> <jj7peu$g3o$1@dont-email.me> <12360032.6313.1331129642322.JavaMail.geo-discussion-forums@vbgu10> <jj80vp$ogr$1@speranza.aioe.org>

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In article <jj80vp$ogr$1@speranza.aioe.org>,
Rui Maciel  <rui.maciel@gmail.com> wrote:
>Maarten wrote:
>
>> As Donald Knuth once put it: "There is no doubt that the grail
>> of efficiency leads to abuse. Programmers waste enormous amounts
>> of time thinking about, or worrying about, the speed of noncritical
>> parts of their programs, and these attempts at efficiency actually
>> have a strong negative impact when debugging and maintenance are
>> considered. We should forget about small efficiencies, say about
>> 97% of the time: premature optimization is the root of all evil."
>> 
>> Only start optimizing once you have tested your code, and are
>> satisfied that it is correct. And only start to optimize when
>> you have seen that there is a performance issue, and have
>> pinpointed the issue with a profiler.
>> 
>> Yes, Donald Knuth leaves you 3% where it does matter. But he
>> also states that you should only worry about that after you
>> have identified that code.
>> 
>> Article can be found from
>> http://en.wikipedia.org/wiki/Program_optimization
>
>Knuth's quote tends to be abused a bit.  Some individuals employ it to, 
>under Knuth's authority, imply that any attention to efficiency, however 
>remote it might be, is also evil, and therefore no attention whatsoever 
>should be ever paid to it.  This may pose a serious problem in applications 
>which do need to run efficiently, as it isn't possible to fix performance 
>problems caused by fundamental design decisions by postponing any attention 
>to the application's efficiency to a testing stage.

The key is the difference between premature optimization and premature
pessimization.  Sutter/Alexandrescu did follow their "Don't optimize
prematurely" with a "Don't pessimize prematurely".  They were also
careful to define premature optimization as making code more complex
and less readable when it is not justified by a *proven* performance
need (my emphasis).

however, all other things being equal, you should know more efficient
patterns and use them naturally if there are no negative cost to using
them. This may be as simple as passing read-only parameters as const
reference rather than by value and forcing a copy. OTOH, manually
implementing a ring buffer and maniplulating internal data with
pointer arithmetic because one believe that std::vector might not be
as fast is not justfiable without measurements.

Yannick

Thread

use of pointers ahso <ahso47@yahoo.com> - 2012-03-06 02:54 -0800
  Re: use of pointers Marcel Müller <news.5.maazl@spamgourmet.com> - 2012-03-06 12:22 +0100
    Re: use of pointers nick_keighley_nospam@hotmail.com - 2012-03-07 00:32 -0800
      Re: use of pointers Juha Nieminen <nospam@thanks.invalid> - 2012-03-07 13:47 +0000
        Re: use of pointers nick_keighley_nospam@hotmail.com - 2012-03-07 07:06 -0800
          Re: use of pointers Juha Nieminen <nospam@thanks.invalid> - 2012-03-07 16:04 +0000
  Re: use of pointers Juha Nieminen <nospam@thanks.invalid> - 2012-03-06 12:29 +0000
    Re: use of pointers Victor Bazarov <v.bazarov@comcast.invalid> - 2012-03-06 08:04 -0500
      Re: use of pointers glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-03-06 14:05 +0000
        Re: use of pointers Victor Bazarov <v.bazarov@comcast.invalid> - 2012-03-06 11:25 -0500
          Re: use of pointers glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-03-06 20:56 +0000
      Re: use of pointers SG <s.gesemann@gmail.com> - 2012-03-06 06:27 -0800
        Re: use of pointers BGB <cr88192@hotmail.com> - 2012-03-06 13:05 -0700
        Re: use of pointers woodbrian77@gmail.com - 2012-03-07 05:38 -0800
      Re: use of pointers Rui Maciel <rui.maciel@gmail.com> - 2012-03-07 15:48 +0000
        Re: use of pointers BGB <cr88192@hotmail.com> - 2012-03-07 18:38 -0700
          Re: use of pointers Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2012-03-10 21:10 -0500
            Re: use of pointers Jeff Flinn <TriumphSprint2000@hotmail.com> - 2012-03-12 08:26 -0400
              Re: use of pointers Jeff Flinn <TriumphSprint2000@hotmail.com> - 2012-03-12 12:28 -0400
      Re: use of pointers Nobody <nobody@nowhere.com> - 2012-03-09 21:28 +0000
  Re: use of pointers Geoff <geoff@invalid.invalid> - 2012-03-06 21:31 -0800
    Re: use of pointers Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-03-07 11:26 +0000
      Re: use of pointers yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2012-03-07 13:56 +0000
        Re: use of pointers Maarten <maarten.sneep@knmi.nl> - 2012-03-07 06:14 -0800
          Re: use of pointers Rui Maciel <rui.maciel@gmail.com> - 2012-03-07 16:05 +0000
            Re: use of pointers yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2012-03-08 10:08 +0000
              Re: use of pointers Rui Maciel <rui.maciel@gmail.com> - 2012-03-08 21:17 +0000
            Re: use of pointers Maarten <maarten.sneep@knmi.nl> - 2012-03-08 04:55 -0800
          Re: use of pointers Nobody <nobody@nowhere.com> - 2012-03-09 21:45 +0000
        Re: use of pointers Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-03-07 20:08 +0000
      Re: use of pointers Nobody <nobody@nowhere.com> - 2012-03-09 21:50 +0000
        Re: use of pointers Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-03-09 22:37 +0000
  Re: use of pointers Rui Maciel <rui.maciel@gmail.com> - 2012-03-07 15:37 +0000

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