[Numpy-discussion] Solaris Sparc build broken
Charles R Harris
charlesr.harris at gmail.com
Thu Nov 5 02:47:26 EST 2009
On Thu, Nov 5, 2009 at 12:09 AM, David Cournapeau <
david at ar.media.kyoto-u.ac.jp> wrote:
> Charles R Harris wrote:
> >
> >
> > On Wed, Nov 4, 2009 at 11:39 PM, David Cournapeau
> > <david at ar.media.kyoto-u.ac.jp <mailto:david at ar.media.kyoto-u.ac.jp>>
> > wrote:
> >
> > Charles R Harris wrote:
> > >
> > >
> > > On Wed, Nov 4, 2009 at 11:30 PM, David Cournapeau
> > > <david at ar.media.kyoto-u.ac.jp
> > <mailto:david at ar.media.kyoto-u.ac.jp>
> > <mailto:david at ar.media.kyoto-u.ac.jp
> > <mailto:david at ar.media.kyoto-u.ac.jp>>>
> > > wrote:
> > >
> > > Charles R Harris wrote:
> > >
> > > >
> > > > I don't think it's that bad. Leaving out the ppc and
> > sticking to
> > > ieee,
> > > > there is only double precision, extended precision and quad
> > > precision
> > > > versions of long double and they are easily determined at
> > run time.
> > >
> > > How would you determine this at runtime ?
> > >
> > >
> > > Excepting the PPC, just loop adding a number to one, dividing it by
> > > two at each iteration, and stop when the result is equal to one.
> >
> > But that's not what I need. I need to know exactly the binary
> > representation: how many bits in the mantissa/exponent and where, the
> > exponent, where does subnormals start, the range of NAN
> > representations,
> > etc...
> >
> >
> > It tells you how many bits are in the mantissa, and given ieee the
> > rest follows. We only support ieee anyway.
>
> But is this reliable ? It does not seem to work for long double in
> intel, for example (but seems to work for sparc64, at least using qemu).
>
>
Works fine here:
#include <stdio.h>
int main(int argc, char **args)
{
long double tol;
int i;
for (i = 0, tol = 1; 1 + tol != 1; tol /=2, i++);
printf("count: %d\n", i - 1);
return 0;
}
$[charris at ubuntu ~]$ gcc precision.c
$[charris at ubuntu ~]$ ./a.out
count: 63
That's 63+1 for the mantissa, which is what intel extended precision is.
Chuck
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/numpy-discussion/attachments/20091105/13b89cb4/attachment.html>
More information about the NumPy-Discussion
mailing list