Gonzalo Tornaria wrote:
> On Wed, Dec 30, 2009 at 10:38 PM, Dr. David Kirkby
> <david.kir...@onetel.net> wrote:
>> Em, This is very odd. exp(1) gives a different result on SPARC if you build
>> with gcc or Sun Studio. GCC is correct, and Sun Studio is wrong. Yet Sage on
>> 't2' was build with gcc, not Sun Studio.
>
> gcc is actually inlining exp(1.0) to its correct value. The exp() from
> the sun library is incorrect. Try this program instead:
>
> #include <math.h>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main(int argc, char **argv) {
> double x = 1.0;
> if (argc>1)
> x = atof(argv[1]);
> printf("%.16lf\n",exp(x));
> }
>
> Best, Gonzalo
>
Hi,
Thank you. Yes, your version forces a call to the library, which does give the
less accurate result (2.7182818284590455). The data below is on my own SPARC,
not 't2', but results should be the same.
drkir...@kestrel:~$ gcc -lm exp.c
drkir...@kestrel:~$ ./a.out
2.7182818284590451
drkir...@kestrel:~$ gcc -lm exp2.c
drkir...@kestrel:~$ ./a.out
2.7182818284590455
Da
I believe you have got to the bottom of this now.
I also noted that if I try to compile and link my version, without linking in
the maths library, so it compiles and links fine. But if I try your version
(which I called exp2.c), the link fails.
bash-3.2$ gcc exp.c
bash-3.2$ gcc exp2.c
Undefined first referenced
symbol in file
exp /var/tmp//cc2qaGNG.o
ld: fatal: symbol referencing errors. No output written to a.out
collect2: ld returned 1 exit status
Dave
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