Re: log1pl missing?

[Tobias Nygren <tnn%NetBSD.org@localhost>]

On Thu, 11 Aug 2022 14:18:20 -0400
Greg Troxel <gdt%lexort.com@localhost> wrote:

> Has anyone else been having this problem?

It's a known defect in NetBSD's libm.

> Any reason I shouldn't just define it and call log1p, not worrying about
> those extra bits, to get around this (in my local build)?

If you want to lose less precision I believe it is better
to do "logl(1.0l + x)" than "(long double)log1p(x)".
But with homeassistant not being a scientific software I
guess it don't matter much. Are you sure the issue is with
numpy and not scipy? There is a patch for this issue in
pkgsrc scipy.

> Anyone up for doing it right?

Does FreeBSD have an implementation in their libm?
POSIX permits to just use the naive logl(1+x) implementation but
the existence of log1p implies there exists a better precision
numerical algorithm for x near 0.

-Tobias