Mailinglist Archive: opensuse-programming (84 mails)

["William A. Mahaffey III" <wam@xxxxxxxxxx>]

John Lamb wrote:

> Colin Carter wrote:
>
> > Does anybody know if SuSE 64 bit system is really 64 bit code?
> > I can't seem to get any response from SuSE staff regarding the 
> > questions:
> > 1: If I define   int i;  and real x;
> >    do I get 64 bit integer and float if compiled under 64?
>
>
> Try it and see:
>
> #include<stdio.h>
> int main() {
>   printf( "short has size %d\n", sizeof( short ) );
>   printf( "int has size %d\n", sizeof( int ) );
>   printf( "long has size %d\n", sizeof( long ) );
>   printf( "long long long has size %d\n", sizeof( long long ) );
>   printf( "float has size %d\n", sizeof( float ) );
>   printf( "double has size %d\n", sizeof( double ) );
> }
>
> A 32-bit system will give 2 for short, 4 for int, long and float and 
> and 8 for long long and  double. A 64-bit system ought to give 
> different values. Remember that C also specifies bounds for some of 
> these values; so short isn't going to have size 8 just because you've 
> got 64-bit code.
>
> > 2: Where does one find the definitions in the SuSE system?
> >    For example, where is the definition for the structure of
> >    XSizeHints ?
> >    Where is the definition of the function prototypes for the
> >    64 bit functions?
>
>
> Typically somewhere in the /usr/include hierarchy.
>
> > Maybe the 'average' programmer can ignore such issues, but I
> > want to use FORTRAN to do the number crunching and I need to
> > know if I should pass an integer(KIND=4) or integer(KIND=8)
>
>
> I don't suppose there's any way I could persuade you to try using C++ 
> or C instead of FORTRAN (I gave up FORTRAN in 1988 and haven't looked 
> back). If you're calling C functions, then I guess you just look for 
> the declarations in an include directory and use the program above 
> (compile it gcc name.c and run it ./a.out) to identify the actual sizes.

FORTRAN is still as much as 75% faster than C/C++ with good compilers 
(SGI & Intel under various linuces, including SuSE), I have seen that 
without fail. If you are doing runs which take days to complete, the 
difference definitely counts.