On Tue, Nov 25, 2025 at 10:47 AM Sebastian Berg <[email protected]>
wrote:

> On Mon, 2025-11-24 at 10:33 -0800, Amelia Thurdekoos wrote:
> > > ...could we at least try to use the bit width in the name such as
> > > float16
> > > as much as possible?
> >
> >
> >  This is all excellent feedback, thank you! I agree, more explicit is
> > better. Planning as best as we can with an eye to future clarity,
> > seems
> > reasonable.
> >
> >
> > > The important part here seems to be pushing the goal of getting rid
> > > of
> > > npy_math, what is the plan for the rest of it here?  Just getting
> > > rid
> > > of it completely because it is obsolete?
> >
> >
> >
> > If we introduce this now users will adopt it in 2-3 years (old NumPy
> > > versions don't have it).
> > > Now there is no guarantee that e.g. `float16_t` will be generally
> > > supported (it's optional anyway) but if the situation around half
> > > improves just a little, I wonder if by the time this is useful it
> > > won't
> > > already be completely obsolete, rather than just mostly.
> >
> >
> > Thanks for the feedback Sebastian! I agree, the overarching goal is
> > removing npy_math. This proposal's scope is intentionally limited to
> > the
> > float16/halffloat part as one self-contained step in that direction,
> > rather
> > than trying to solve the whole npy_math feature at once. I am not
> > going to
> > be removing any part of the library as part of this effort.
> >
> > If float16 improves enough that this API becomes obsolete, or even
> > less
> > attractive, this effort still yields a net positive. It will assist
> > with
> > reducing the need to link against npy_math.
> >
>
>
> Yeah, nice and I agree with Nathan that it is tedious for e.g. DType
> casts. ml_dtypes uses the Eigen for this purpose CuPy vendors [1].
>
> If `npy_math` wouldn't be deleted it would be nice to have a thought on
> what happens with it (since we could probably use the same thing for
> half).  But I think the hope is to just delete and I don't want to
> block this if this seems like the main blocker.
>

To keep us on the same page: `libnpymath`, not `npy_math.h` (the latter
exposes functionality that doesn't need the static library as well). But
indeed - ideally we'd like to move as many users as possible off of the
static library, so we can just delete it. We managed for `statsmodels`
recently; `scipy` still is tricky and it may need to vendor some code. The
other plan is to do what we do sometimes for legacy code and split it off
as a standalone package that remaining users can then vendor. We already
had this in progress quite a while back, that effort just stalled for now.
See https://github.com/numpy/libnpymath



> However, it still seems to me like only the conversions are (for now?)
> truly useful. And I also still wonder if header-only may not be just as
> well and simpler for all sides?
> I would also be happy to consider to only keep the conversion functions
> and ask users who need serious math to look elsewhere, because for now
> I still suspect it's not hard to find things elsewhere (e.g. Eigen).

(Yes, I am assuming that would throw at least close to zero
> persons/projects under the bus if this starts missing.)
>

I'm not sure something like Eigen is a reasonable thing to point to, that's
a very heavy dependency. That said, I don't think we need to either, since
the header-only approach seems to work.

Cheers,
Ralf


>
> - Sebastian
>
> [1] For now CuPy never compiled against NumPy, if it does there are
> better replacements, i.e. CuPy wouldn't need this functionality.
>
>
> > - Amelia
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