accuracy of asinh and atanh

[Artem Pelenitsyn]

Thanks David! Indeed, here is the commit and ticket:

https://github.com/ghc/ghc/commit/3ea33411d7cbf32c20940cc72ca07df6830eeed7
https://ghc.haskell.org/trac/ghc/ticket/14927

This concerns only `asinh` though. The implementation is closer to what
Matt proposes in his package but simpler. Nevertheless, the original issue
about `Infinity` on large negative numbers seems to be fixed with this.

So, I guess, feel free to kill the patch.

--
Best, Artem

On Thu, 2 Aug 2018 at 23:19 David Feuer <david at well-typed.com> wrote:

> Wasn't there a very recent commit to improve these functions, by
> leftaroundabout?
>
> On Thursday, August 2, 2018 8:16:10 AM EDT Artem Pelenitsyn wrote:
> > Here is the patch: https://phabricator.haskell.org/D5034
> >
> > --
> > Best, Artem
> >
> > On Thu, 2 Aug 2018 at 06:26 Artem Pelenitsyn <a.pelenitsyn at gmail.com>
> wrote:
> >
> > > I'd be willing to do this.
> > >
> > > --
> > > Best wishes,
> > > Artem
> > >
> > >
> > > On Thu, 2 Aug 2018, 04:38 Matt Peddie, <mpeddie at gmail.com> wrote:
> > >
> > >> Thanks, Ben, for chiming in.  I think calling out to C for these
> > >> functions is the way to go if it's now feasible.  (Calling out to libm
> > >> is the workaround I'm using in the application that led me to discover
> > >> the inaccuracy.)
> > >>
> > >> Matt
> > >>
> > >> On Thu, Aug 2, 2018 at 11:33 AM, Ben Gamari <ben at smart-cactus.org>
> wrote:
> > >> > Matt Peddie <mpeddie at gmail.com> writes:
> > >> >
> > >> >> Hi George,
> > >> >>
> > >> >> Not a stupid question.  I don't have a single source at hand, but I
> > >> >> think I read in a few places on the wiki that calling out to the
> > >> >> system math library is not an option due to the variety of system
> math
> > >> >> libraries on the platforms GHC supports.  It'd be great if I got
> the
> > >> >> wrong impression and this could just be a call to C.  Can anyone
> set
> > >> >> me straight on this point?
> > >> >>
> > >> > Indeed it's not a stupid question at all. Indeed this is precisely
> what
> > >> > we do for the simpler transcendentals (e.g. sin, asin, log). We very
> > >> > well could move in this direction in the case of asinh/atanh as
> well. I
> > >> > believe the reason we don't currently is that atanh was only
> > >> > standardized in C99, which we only started requiring a few releases
> ago.
> > >> > Perhaps this is ultimately the right direction.
> > >> >
> > >> > Cheers,
> > >> >
> > >> > - Ben
> > >> _______________________________________________
> > >> ghc-devs mailing list
> > >> ghc-devs at haskell.org
> > >> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
> > >>
> > >
> >
>
>
> --
> David Feuer
> Well-Typed
>
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