Mailinglist Archive: opensuse-programming (118 mails)

[Jerry Feldman <gaf@xxxxxxx>]

On Tuesday 19 April 2005 10:09 am, Colin Carter wrote:
> Jerry also mentioned the correct use of multiples of "natural" units.
> I think I will use 64 bit integers (on my AMD64) because I think it ought
> to be faster than 32 bit, and memory is 'cheaper' than cpu speed, and one
> pays for memory once, but for cpu time every time you run the code.
64-bit systems generally use the LP64 method, which means that both pointers 
and long integers are 64-bits while int remains at 32-bits. Most Unix and 
Linux systems use this. You will not pay a penalty for using a 32-bit int.  
C and C++ will automatically align your data for you:
struct {
	char a;	/* aligned on at least a 64-bit boundary probably 128 */
	long b;	/* aligned on a 64-bit boundary */
};
The above structure is 16 bytes long with 7 bytes inserted as a filler 
between a and b. (on a 32-bit system, the filler would be 3 bytes). 
-- 
Jerry Feldman <gaf@xxxxxxx>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
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