Re: [gfortran] PR15206 RRSPACING wrong for zero

[Tobias Schlüter <tobias dot schlueter at physik dot uni-muenchen dot de>]

Paul Brook wrote:
> On Saturday 08 May 2004 17:28, Tobias Schlüter wrote:
>
> > This patch fixes the RRSPACING intrinsic. It didn't return the correct
> > result for a zero argument. I don't really understand how the original
> > code worked, but I verified that RRSPACING(x) == x/SPACING(x) for a wide
> > range of arguments. I used the condition (expn == 0 && frac == 0) to
> > check for a zero argument, if this is not the correct check, please
> > correct this.
>
>
> I think frac==0 is a sufficient test. The result of clz(0) is undefined, so we 
> want to avoid that anyway

I was afraid that frac == 0 for 1.0 as well, because the leading 1 is 
not recorded in FPNs. Of course, exp would be zero in that case as well. 
I'll try only checking frac == 0, and report back.

BTW the optimizers don't believe that
 x / (SPACING(x) * RRSPACING(x)) == 1 :-)

- Tobi

ps I'm still in town, I postponed my vacation. I'm not in some internet 
cafe manically applying patch after patch :-)