Re: Generally, are the programs written by C++ slower than written by C 10% ?

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From	Ian Collins <ian-news@hotmail.com>
Newsgroups	comp.lang.c++
Subject	Re: Generally, are the programs written by C++ slower than written by C 10% ?
Date	Tue, 06 Sep 2011 07:51:19 +1200
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On 09/ 6/11 07:34 AM, BGB wrote:
> On 9/5/2011 12:28 AM, Nick Keighley wrote:
>> On Sep 3, 9:45 am, BGB<cr88...@hotmail.com>   wrote:
>>
>> If I'm coding in C and I want to sort something. My first thought
>> would be qsort()! If it was too slow only then would I consider hand
>> coding it. Surely any constructively lazy person would use an existing
>> facility rather hand-roll their own!
>>
>
> different styles for different sorts...
>
>
> actually, in my case I would probably far more likely copy-paste it and
> then edit it to the new use.
>
> copy-paste is a powerful tool which is often disparaged and overlooked.

Rightly so.  C has things call functions that enable code to be reused 
and C++ has function templates that remove the last excuse for copy and 
paste.

> but, one would typically write it themselves initially (before
> subjecting it to endless copy-paste).

Not if they were being paid to deliver software.

>>> it is also not clear that std::string would be, in general, faster, and
>>> having an O(1) ability to fetch the length may turn out to be moot if
>>> most other operations tend towards being more expensive.
>>
>> are they?
>>
>
> from what I have seen, people tend to pass them around by-value.

Most C++ code passes strings by const reference.

> apparently, the by-value vs by-reference thing makes a bit of a
> difference WRT performance.
>
> apparently, their performance characteristics also differ some between
> GCC and MSVC, with the ones in MSVC apparently tending to be more expensive.
>
> granted, I haven't personally looked into all of this in-depth though.

With some compilers in some modes, passing a string by value will be 
quicker if the string object (typically a pair of pointers) is small 
enough to pass in registers.

> there are also plenty of things often done with C strings as well that
> can make them faster, such as interning them so that one can check
> string equality using '==' on the pointers, rather than using
> "!strcmp()", ...

In other words, wrapping them like std::string...

> in my case, I tend to avoid "stdrup()" as well, as generally "strdup()"
> is a good way to "make bad things happen" (slow, tears through huge
> amounts of memory, leaves the program responsible to free them, ...), so
> preferable IMO is interning them into string-tables (a big glob of
> memory where they are packed end-to-end).
>
> then one can free the whole string table as part of a "teardown" process.
>
> another strategy (used elsewhere) is to allocate the strings in the
> garbage-collected heap (I use GC), and then manage them using a weak
> hash (entries will be reset to NULL whenever any are reclaimed by the GC).
>
>
> also, == and != work provided both strings are in the same string-table.

Or save a whole lot of pain and use std::string.

-- 
Ian Collins

Thread

Generally, are the programs written by C++ slower than written by C 10% ? KaiWen <wenkai1987@gmail.com> - 2011-09-01 01:41 -0700
  Re: Generally, are the programs written by C++ slower than written by C   10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-01 21:15 +1200
  Re: Generally, are the programs written by C++ slower than written by C 10% ? "Fred Zwarts \(KVI\)" <F.Zwarts@KVI.nl> - 2011-09-01 11:48 +0200
    Re: Generally, are the programs written by C++ slower than written by C 10% ? Joshua Maurice <joshuamaurice@gmail.com> - 2011-09-01 15:34 -0700
      Re: Generally, are the programs written by C++ slower than written by C 10% ? KaiWen <wenkai1987@gmail.com> - 2011-09-01 19:09 -0700
        Re: Generally, are the programs written by C++ slower than written by   C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-02 14:39 +1200
        Re: Generally, are the programs written by C++ slower than written by C 10% ? Krice <paulkp@mbnet.fi> - 2011-09-01 22:33 -0700
        Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-02 01:12 -0500
          Re: Generally, are the programs written by C++ slower than written by C 10% ? James Kanze <james.kanze@gmail.com> - 2011-09-03 15:25 -0700
            Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-04 01:34 -0500
              Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-04 02:33 -0700
              Re: Generally, are the programs written by C++ slower than written by C 10% ? James Kanze <james.kanze@gmail.com> - 2011-09-04 11:00 -0700
        Re: Generally, are the programs written by C++ slower than written by C 10% ? Goran <goran.pusic@gmail.com> - 2011-09-01 23:23 -0700
          Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-02 03:00 -0700
            Re: Generally, are the programs written by C++ slower than written by C 10% ? Goran <goran.pusic@gmail.com> - 2011-09-02 09:39 -0700
          Re: Generally, are the programs written by C++ slower than written by C 10% ? Rui Maciel <rui.maciel@gmail.com> - 2011-09-02 12:44 +0100
        Re: Generally, are the programs written by C++ slower than written by C 10% ? Rui Maciel <rui.maciel@gmail.com> - 2011-09-02 09:59 +0100
          Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-02 11:25 -0700
        Re: Generally, are the programs written by C++ slower than written by C 10% ? Juha Nieminen <nospam@thanks.invalid> - 2011-09-03 05:51 +0000
          Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-03 01:45 -0700
            Re: Generally, are the programs written by C++ slower than written   by C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-03 20:53 +1200
              Re: Generally, are the programs written by C++ slower than written   by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-03 10:49 -0700
                Re: Generally, are the programs written by C++ slower than written     by C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-04 08:15 +1200
                Re: Generally, are the programs written by C++ slower than written     by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-03 17:50 -0700
            Re: Generally, are the programs written by C++ slower than written by C 10% ? Juha Nieminen <nospam@thanks.invalid> - 2011-09-03 16:28 +0000
              Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-03 10:42 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? "Bo Persson" <bop@gmb.dk> - 2011-09-04 11:34 +0200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-04 09:04 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Juha Nieminen <nospam@thanks.invalid> - 2011-09-04 18:04 +0000
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Keith H Duggar <duggar@alum.mit.edu> - 2011-09-04 18:44 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-04 23:26 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Juha Nieminen <nospam@thanks.invalid> - 2011-09-05 08:01 +0000
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-05 11:45 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Juha Nieminen <nospam@thanks.invalid> - 2011-09-06 06:30 +0000
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-06 07:22 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-06 16:25 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-06 07:14 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-07 12:28 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-07 16:49 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Noah Roberts <roberts.noah@gmail.com> - 2011-09-07 18:45 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-08 15:56 -0700
            Re: Generally, are the programs written by C++ slower than written by C 10% ? James Kanze <james.kanze@gmail.com> - 2011-09-03 15:32 -0700
              Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-03 19:16 -0700
            Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-05 00:28 -0700
              Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-05 12:34 -0700
                Re: Generally, are the programs written by C++ slower than written   by C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-06 07:51 +1200
                Re: Generally, are the programs written by C++ slower than written   by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-05 14:06 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-06 00:32 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-06 07:33 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-07 02:52 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-08 16:24 -0700
                Re: Generally, are the programs written by C++ slower than written   by C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-09 11:38 +1200
                Re: Generally, are the programs written by C++ slower than written   by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-08 21:39 -0700
                Re: Generally, are the programs written by C++ slower than written     by C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-09 19:01 +1200
                Re: Generally, are the programs written by C++ slower than written     by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-09 02:45 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-09 03:23 -0700
                Re: Generally, are the programs written by C++ slower than written     by C 10% ? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-09-14 23:12 +0000
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-09 02:40 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-09 11:19 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-09 15:42 -0500
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-09 14:24 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Noah Roberts <roberts.noah@gmail.com> - 2011-09-09 18:22 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-10 10:11 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Noah Roberts <roberts.noah@gmail.com> - 2011-09-10 10:54 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-10 14:28 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-11 12:29 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-11 00:45 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Joshua Maurice <joshuamaurice@gmail.com> - 2011-09-12 00:39 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-12 18:06 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Joshua Maurice <joshuamaurice@gmail.com> - 2011-09-12 16:46 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-13 10:20 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Joshua Maurice <joshuamaurice@gmail.com> - 2011-09-13 13:16 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nobody <nobody@nowhere.com> - 2011-09-11 04:53 +0100
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-11 14:51 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-10 07:46 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? KaiWen <wenkai1987@gmail.com> - 2011-09-06 03:10 -0700
                Re: Generally, are the programs written by C++ slower than written by   C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-06 22:50 +1200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? KaiWen <wenkai1987@gmail.com> - 2011-09-06 04:48 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2011-09-07 09:45 +0000
                Re: Generally, are the programs written by C++ slower than written by   C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-07 21:51 +1200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? KaiWen <wenkai1987@gmail.com> - 2011-09-08 00:15 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2011-09-08 12:14 +0000
                Re: Generally, are the programs written by C++ slower than written by C 10% ? KaiWen <wenkai1987@gmail.com> - 2011-09-08 07:14 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Asger-P <junk@asger-p.dk> - 2011-09-06 13:52 +0200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-06 11:47 -0500
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-06 11:50 -0500
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Asger-P <junk@asger-p.dk> - 2011-09-06 21:04 +0200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Leigh Johnston <leigh@i42.co.uk> - 2011-09-06 20:37 +0100
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-06 15:10 -0500
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Leigh Johnston <leigh@i42.co.uk> - 2011-09-06 21:14 +0100
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Asger-P <junk@asger-p.dk> - 2011-09-07 00:40 +0200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Leigh Johnston <leigh@i42.co.uk> - 2011-09-06 23:59 +0100
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Noah Roberts <roberts.noah@gmail.com> - 2011-09-06 16:26 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-06 14:55 -0500
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Asger-P <junk@asger-p.dk> - 2011-09-07 00:51 +0200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Paavo Helde <myfirstname@osa.pri.ee> - 2011-09-06 23:29 -0500
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Asger-P <junk@asger-p.dk> - 2011-09-07 09:06 +0200
                Re: Generally, are the programs written by C++ slower than written by   C 10% ? Ian Collins <ian-news@hotmail.com> - 2011-09-07 19:09 +1200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nobody <nobody@nowhere.com> - 2011-09-07 13:19 +0100
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Juha Nieminen <nospam@thanks.invalid> - 2011-09-07 13:01 +0000
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Rui Maciel <rui.maciel@gmail.com> - 2011-09-07 14:26 +0100
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Asger-P <junk@asger-p.dk> - 2011-09-07 15:49 +0200
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-08 22:49 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Miles Bader <miles@gnu.org> - 2011-09-09 15:25 +0900
                Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-09 02:50 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-09 03:26 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-09 03:25 -0700
                Re: Generally, are the programs written by C++ slower than written by C 10% ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-06 00:24 -0700
            Re: Generally, are the programs written by C++ slower than written by C 10% ? yatremblay@bel1lin202.(none) (Yannick Tremblay) - 2011-09-06 13:57 +0000
              Re: Generally, are the programs written by C++ slower than written by C 10% ? BGB <cr88192@hotmail.com> - 2011-09-06 08:18 -0700
        Re: Generally, are the programs written by C++ slower than written by C 10% ? Nobody <nobody@nowhere.com> - 2011-09-03 08:34 +0100
  Re: Generally, are the programs written by C++ slower than written by C 10% ? "A" <a@a.a> - 2011-09-01 11:50 +0200
  Re: Generally, are the programs written by C++ slower than written by C 10% ? Rui Maciel <rui.maciel@gmail.com> - 2011-09-01 10:53 +0100
  Re: Generally, are the programs written by C++ slower than written by C 10% ? James Kanze <james.kanze@gmail.com> - 2011-09-03 15:11 -0700

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