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

Fri May 1 03:10:26 CEST 2020

I have now created a page about this:

http://mac.r-project.org/openmp

which also provides libomp binaries for all recent versions of Xcode (and more).

Important note: this is about Xcode - it is NOT about using Homebrew tools nor the custom compilers we used before R 4.0.0. Both of the latter are not suitable for use with R 4.0.0 binaries.

Please give it a shot. Thanks for those participating in the discussion.

Cheers,
Simon

> On 1/05/2020, at 2:23 AM, Wright, Erik Scott <ESWRIGHT using pitt.edu> wrote:
> 
> Hi Kevin et al.,
> 
> The setup you suggested did not work for me, but I was able to get OpenMP to work on Mac (10.13) with R v4.0 packages.  Here's what I did:
> 
> (1) After installing Homebrew, ran
> brew install libomp
> # Note it is also possible to install from OpenMP Source code: https://releases.llvm.org/download.html#10.0.0
> (2) Determined the install path with
> brew --prefix libomp
> # In my case /usr/local/opt/libomp
> (3) Added lines to ~/.R/Makevars
> CC=/usr/local/clang4/bin/clang -fopenmp -I/usr/local/opt/libomp/include
> LDFLAGS=-L/usr/local/opt/libomp/lib
> 
> I imagine the process is similar for C++ code by setting CXX.  Now parallelization for C code with OpenMP is working again on Mac.
> 
> As always, I am thankful to the R community for helping problem solve.
> 
> I wish more direction along these lines could be added to mac.r-project.org
> 
> Erik
> 
> 
>> On Apr 29, 2020, at 1:51 AM, Dmitriy Selivanov <selivanov.dmitriy using gmail.com> wrote:
>> 
>> 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
> 