[R-SIG-Mac] OpenMP on CRAN (Simon Urbanek)

[Dmitriy Selivanov]

Thanks, Kevin, I can confirm suggested setup works fine so far. Thank you!

I understand it, is that there's
> no guarantee that this will work properly (or continue to work
> properly) as the Apple toolchain continues to be updated -- e.g. a new
> version of macOS / Xcode could install a version of Apple Clang that
> is then incompatible with the version of libomp currently in use. In
> such a case, I suspect one would need to find and reinstall libomp.


Thats understandable.

On Sat, Apr 25, 2020 at 8:09 PM Kevin Ushey <kevinushey using gmail.com> wrote:

> The following works for me on macOS 10.15.4 using Apple Clang + libomp
> from LLVM 10 (via Homebrew).
>
> Install libomp from Homebrew with:
>
>     brew install libomp
>
> Then, put the following in ~/.R/Makevars
>
>     CPPFLAGS += -I/usr/local/opt/libomp/include -Xclang -fopenmp
>     LDFLAGS += -L/usr/local/opt/libomp/lib -lomp
>
> Then R will automatically enable + use OpenMP as appropriate when
> installing packages from sources.
>
> The main danger of this approach, as I understand it, is that there's
> no guarantee that this will work properly (or continue to work
> properly) as the Apple toolchain continues to be updated -- e.g. a new
> version of macOS / Xcode could install a version of Apple Clang that
> is then incompatible with the version of libomp currently in use. In
> such a case, I suspect one would need to find and reinstall libomp.
>
> In theory, this could be alleviated by ensuring all users download and
> use the same version of Xcode as is being used by the macOS build
> machine (Xcode 10.1), but in practice users will likely just be using
> the "default" set of command line tools that comes with their version
> of macOS.
>
> Cunningham's law will hopefully ensure someone else will chime in if
> I've got something wrong :-)
>
> Best,
> Kevin
>
> On Sat, Apr 25, 2020 at 8:29 AM Wright, Erik Scott <ESWRIGHT using pitt.edu>
> wrote:
> >
> > I second this request.  Dropping OpenMP support in R v4.0 on Mac is
> unfortunate.  My R package is highly parallelized via OpenMP, and many of
> my end-users take advantage of the excellent speedups.  It would be much
> appreciated if user-level instructions could be provided for how to enable
> OpenMP support on the Mac.
> >
> > Thanks,
> > Erik
> >
> >
> > > On Apr 23, 2020, at 7:08 AM, Dmitriy Selivanov <
> selivanov.dmitriy using gmail.com> wrote:
> > >
> > > Hi Simon,
> > >
> > > Just wanted follow up on this topic.
> > >
> > > It would be very helpful if you can provide some guide on
> > >
> https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmac.r-project.org%2F&data=02%7C01%7Ceswright%40pitt.edu%7C65097590dea4453ab8cf08d7e776b868%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C637232369415901734&sdata=qlhXuEubgD6PNmkbD%2BWQy5OI9X%2BGjxSYHMNjA%2BQHZzI%3D&reserved=0
> <
> https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmac.r-project.org%2F&data=02%7C01%7Ceswright%40pitt.edu%7C65097590dea4453ab8cf08d7e776b868%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7C0%7C637232369415911728&sdata=5XR5LJuAKu4%2B3%2FUHsWVPMlyXTLY87P6OF%2FP%2FTZt1W8Y%3D&reserved=0>
> for those users
> > > (advanced?) and developers who wants to be able to use OpenMP on mac.
> From
> > > what I've understood from this mail thread the easiest way is to
> install R
> > > from homebrew as it is built with non-standard Apple toolchain.
> > > Apart from that you've mentioned you may consider to bundle binary
> iomp
> > > with R installation, but "it would be on the package author to make
> sure
> > > that the way the package operates is compatible with that binary".
> Could
> > > you please elaborate on that?
> > >
> > > I believe I'm not alone who would like to be able to use OpenMP on mac
> and
> > > "official" guidance would be very helpful.
> > >
> > > --
> > > Regards
> > > Dmitriy Selivanov
> > >
> > >       [[alternative HTML version deleted]]
> > >
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-- 
Regards
Dmitriy Selivanov

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