[PATCH 0/4] Fix huge error for pow detected by Paul Zimmermann

[Jeff Johnston]

Thanks Andoni and Paul.  Patches pushed to master.

-- Jeff J.

On Thu, Apr 13, 2023 at 10:42 AM Andoni Arregi <andoni.arregui@gtd-gmbh.de>
wrote:

> Dear Paul,
>
> thank *you* for detecting the errors/inaccuracies first (questions are as
> important as the answers) and then
> independently confirming that the patch solves them.
>
> You know how tricky this is and how easy it is to fix something here and
> break it there. That's why such an independent
> verification in addition to our tests is so important :-)
>
> By the way, most of the submitted work is product of the effort of our
> colleague Fabian Schriever.
>
> Best regards
>
> On Thu, 2023-04-13 at 14:16 +0200, Paul Zimmermann wrote:
> >        Hi Andoni,
> >
> > I had time to check this patch series on top of be2749c.
> >
> > I confirm the issue I reported is fixed.
> >
> > In addition, the maximal known error, which was 636 ulps
> > apart from the above issue, has dropped to less than 1 ulp:
> >
> > pow 0 -1 0x1.4c3064d46aef3p-851,-0x1.cef4118ed50c2p-10 [0.893] 0.892119
> 0.8921192373561432
> >
> > Thank you, great work!
> >
> > Paul
> >
> > > From: Andoni Arregi <andoni.arregui@gtd-gmbh.de>
> > > Cc: Andoni Arregi <andoni.arregui@gtd-gmbh.de>
> > > Date: Wed, 12 Apr 2023 17:34:41 +0200
> > >
> > > This patch series fixes in pow the huge error detected by Paul
> > > Zimmermann where x is negative and y is a large odd integer.
> > >
> > > There is also an accuracy fix for cases where x is close to 1 and y is
> > > large.
> > >
> > > Andoni Arregi (4):
> > >   Fix missing sign for overflow/underflow where x is negative and y is
> > >     large odd integer
> > >   Fix x close to 1, y between 2^31 and 2^64
> > >   Compare j as unsigned
> > >   Replace always true if with else
> > >
> > >  newlib/libm/math/e_pow.c | 48 +++++++++++++++++++++-------------------
> > >  1 file changed, 25 insertions(+), 23 deletions(-)
> > >
> > > --
> > > 2.40.0
> > >
> > >
> > >
>
> --
> Andoni Arregi
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