[Numpy-discussion] float128 / longdouble on PPC - is it broken?

Charles R Harris charlesr.harris@gmail....
Tue Oct 25 12:52:36 CDT 2011


On Tue, Oct 25, 2011 at 11:45 AM, Matthew Brett <matthew.brett@gmail.com>wrote:

> Hi,
>
> On Tue, Oct 25, 2011 at 2:43 AM, Pauli Virtanen <pav@iki.fi> wrote:
> > 25.10.2011 06:59, Matthew Brett kirjoitti:
> >> res = np.longdouble(2)**64
> >> res-1
> >> 36893488147419103231.0
> >
> > Can you check if long double works properly (not a given) in C on that
> > platform:
> >
> >        long double x;
> >        x = powl(2, 64);
> >        x -= 1;
> >        printf("%g %Lg\n", (double)x, x);
> >
> > or, in case the platform doesn't have powl:
> >
> >        long double x;
> >        x = pow(2, 64);
> >        x -= 1;
> >        printf("%g %Lg\n", (double)x, x);
>
> Both the same as numpy:
>
> [mb312@jerry ~]$ gcc test.c
> test.c: In function 'main':
> test.c:5: warning: incompatible implicit declaration of built-in function
> 'powl'
>

I think implicit here means that that the arguments and the return values
are treated as integers. Did you #include <math.h>?


> [mb312@jerry ~]$ ./a.out
> 1.84467e+19 3.68935e+19
>
>
Chuck
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