Re: Add error functions: erf() and erfc() - Mailing list pgsql-hackers

From Dean Rasheed
Subject Re: Add error functions: erf() and erfc()
Date
Msg-id CAEZATCX8os75BdCNARewvrbf663HTTqwHKi+D32XzyfkDCoK7A@mail.gmail.com
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In response to Re: Add error functions: erf() and erfc()  (Nathan Bossart <nathandbossart@gmail.com>)
Responses Re: Add error functions: erf() and erfc()  (Nathan Bossart <nathandbossart@gmail.com>)
List pgsql-hackers
On Thu, 9 Mar 2023 at 00:13, Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Wed, Mar 08, 2023 at 11:29:12PM +0000, Dean Rasheed wrote:
> > On Wed, 8 Mar 2023 at 20:11, Nathan Bossart <nathandbossart@gmail.com> wrote:
> >> The man pages for these seem to indicate that underflow can occur.  Do we
> >> need to check for that?
> >
> > No, I don't think so. The docs indicate that if an underflow occurs,
> > the correct result (after rounding) should be returned, so I think we
> > should just return that result (as we do for tanh(), for example).
>
> Makes sense.
>
> I'm also wondering about whether we need the isinf() checks.  IIUC that
> should never happen, but maybe you added that "just in case."
>

I copied those from dtanh(), otherwise I probably wouldn't have
bothered. erf() is always in the range [-1, 1], just like tanh(), so
it should never overflow, but maybe it can happen in a broken
implementation.

Regards,
Dean



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