[R-pkg-devel] SystemRequirements & configure check for FFTW with single precision support

[Lukas Schneiderbauer]

Hi Simon,

Thank you for your detailed feedback!
I rebuilt the configure script to use pkg-config, removed the extra
brew-check, fixed the CPPFLAGS issue you mentioned, and included "fftw-s"
in SystemRequirements.
The package is building fine again on all platforms (using rhub tests and
the `devtools::check_win_devel()` test).

Hopefully it will get accepted soon. :)

Best regards,
Lukas


On Wed, Jan 15, 2025 at 3:59 AM Simon Urbanek <simon.urbanek using r-project.org>
wrote:

> Lukas,
>
> I have not seen the communication so I'm not commenting on that
> specifically, I only looked at the GitHub link.
>
> Although your configure could be improved (more below), it works well
> enough to detect fftw3f.
>
> Unfortunately, SystemRequirements don't have a well-defined structure, but
> there are two commonly used notations:
>
> a) library name and version so in your case that would be something like
> libfftw3f (>=3.3.0)
>
> b) deb/rpm package names
> libfftw3-dev (deb), fftw3-devel (rpm)
>
> fftw is a bit of a mess, because Debian ships the single-precision static
> library in libfftw3-dev, but also has libfftw3-single3 which is the dynamic
> version of the same, while RH does not distinguish. macOS recipe names are
> usually included only if they are non-obvious, but that would be the case
> here since installing fftw recipe does not work for you, so mentioning
> fftw-s is probably a good idea (there are community scripts that try to
> extract that information from the packages so that the dependencies can be
> installed).
>
> As for your configure, my main objection would be that it ignores CPPFLAGS
> (they are not substituted at all even though they *are* used in the tests)
> and doesn't use pkg-config to get the correct flags. (Also the brew part
> should go - it's makes unwarranted assumptions [see below] and is entirely
> superfluous if you use pkg-config instead.) To illustrate what I mean, you
> get
>
> $ pkg-config --cflags fftw3f
> -I/opt/R/x86_64/include
> $ pkg-config --libs fftw3f
> -L/opt/R/x86_64/lib -lfftw3f -lm
>
> while fCWTr on GitHub only uses
>
>   Configuration for fCWTr 0.2.9000
>
>     cppflags:
>     cxxflags:
>     ldflags:
>     libs:     -lfftw3f
>
> It actually works despite that, because R will inject the other flags for
> you, but that will only work is fftw is installed in the same location as
> the other libraries used by R (which is common, but not guaranteed). I
> wouldn't say it is dealbreaker, but it would recommend it for robustness.
>
> FWIW with homebrew the correct flags are obtainable from pkg-config:
>
> $ pkg-config --libs fftw3f
> -L/opt/brew/Cellar/fftw/3.3.8_1/lib -lfftw3f
> $ pkg-config --cflags fftw3f
> -I/opt/brew/Cellar/fftw/3.3.8_1/include
>
> Cheers,
> Simon
>
>
>
> > On Jan 11, 2025, at 10:37 PM, Lukas Schneiderbauer <
> lukas.schneiderbauer using gmail.com> wrote:
> >
> > Hi list,
> >
> > I am working on getting a package <
> https://github.com/lschneiderbauer/fCWTr> to
> > CRAN. It depends on the FFTW library <https://www.fftw.org/> that is
> built
> > with single precision support. I am stuck in the submission process and I
> > require your help.
> >
> > Before I come to my questions, some key facts about the package:
> >
> > The package has an autoconf configure script that uses (among other
> things,
> > like OpenMP checks, etc..) AC_SEARCH_LIBS to check whether required
> > functions of the library 'fftwf' exist, if yes, it adds the corresponding
> > compiler/linker flags; if no, it errs with a descriptive error message.
> >
> > The CRAN Windows as well as Linux build service included fftwf in their
> > fftw build out of the box, and so building there was no problem, R CMD
> > Check passes there. In the past, building for MacOS was more trouble,
> since
> > its fftw package does not include a single-precision build. I reached out
> > to Simon Urbanek, and he was so kind as to add an appropriate new recipe
> > "fftw-s" that provided an fftw version with single precision support. As
> of
> > now, R CMD check also passes cleanly on the MacOS build service, thanks
> to
> > Simon Urbanek's efforts.
> >
> > Now, I am stuck at submission for two reasons:
> > 1. The SystemRequirements specification in the DESCRIPTION file is
> > incorrect.
> > 2. It is said that "the package needs a configure check for fftwf".
> >
> > Add 1.
> > Initially, I had no mention of the "single precision" version of fftw,
> > because I thought it is included everywhere by default. It was stated
> that
> > I need to add that information. I naturally complied.
> > This is my current version:
> > "SystemRequirements: fftw3 (including single precision support fftw3f),
> > fftw3f_omp (optional), OpenMP (optional)"
> > In the second subscription run, I was told to add "fftw-s" since I
> require
> > the fftw-s package on MacOS. This does not make much sense to me since
> > "fftw-s" is only the name of this package on Simon Urbanek's MacOS build
> > service. The library file itself is still called fftwf, like it is on any
> > other platform. If I added "fftw-s", I would also need to explain that
> this
> > is only valid for MacOS which seems to make the SystemRequirements
> > unnecessary verbose.
> > * Can someone explain the reason behind this request to me?
> > * How exactly should I add "fftw-s" to pass the submission process?
> >
> > Add 2.
> > I tried to explain now for the second time in the submission notes, that
> a
> > check is already in place (see the AC_SEARCH_LIBS paragraph above). But
> my
> > explanation gets ignored.
> > * What am I doing wrong?
> > * What additional configure checks do I need to add to the package?
> >
> > Thanks a lot for your help!
> > Sincerely, Lukas Schneiderbauer
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-package-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-package-devel
> >
>
>

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