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Groups > comp.lang.c.moderated > #382

Re: which one is faster?

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On 05.04.2012 01:05, echo ma wrote:
> on a 32bit system.
>
> #pragma pack(4)
> struct TestStruct
> {
> 	unsigned short a;
> 	unsigned short b;
>          unsigned int c;
> };
> #pragma pack()
> struct TestStruct t;
> t.a = 0;      //step 1
> t.b = 1;      //step 2
> t.c = 2;      //step 3
>
> Questing is :  Are these 3 steps having the same perfomance time?

Sorry, I don't understand. To have something "the same", you need to 
compare two different things. So which two "are the same" or "not the 
same"? I see only one piece of code, and this is not even portable. 
(#pragma pack() is not ANSI-C).


Anyhow, before performing micro-optimizations like the one you made 
above, profile your code and identify whether this is really the cause 
of a performance (or memory) problem. You should probably post a more 
complete example to allow any judgement - and measure first before 
trying non-portable constructs.

Greetings,
	Thomas
-- 
comp.lang.c.moderated - moderation address: clcm@plethora.net -- you must
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Thread

which one is faster? echo ma <fatmck@gmail.com> - 2012-04-04 18:05 -0500
  Re: which one is faster? James Kuyper <jameskuyper@verizon.net> - 2012-04-23 08:31 -0500
  Re: which one is faster? "Joel C. Salomon" <joelcsalomon@gmail.com> - 2012-04-23 08:33 -0500
  Re: which one is faster? David Brown <david@westcontrol.removethisbit.com> - 2012-04-23 08:33 -0500
  Re: which one is faster? Thomas Richter <thor@math.tu-berlin.de> - 2012-04-23 08:31 -0500
    Re: which one is faster? Keith Thompson <kst-u@mib.org> - 2012-04-30 21:57 -0500
  Re: which one is faster? Barry Schwarz <schwarzb@dqel.com> - 2012-04-23 08:32 -0500
  Re: which one is faster? Keith Thompson <kst-u@mib.org> - 2012-04-23 08:32 -0500
    Re: which one is faster? George Neuner <gneuner2@comcast.net> - 2012-04-30 21:58 -0500

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