[R-SIG-Mac] Building R 4.0.2 from source via clang/xcode for MKL on macOS

[Simon Urbanek]

Rollin,

it has been several years since I last tested MKL, so take it with a grain of salt, but in general you don't necessarily have to build R with MKL in order to use it - you only need to use --enable-BLAS-shlib and link to any ABI-compatible BLAS which can be vecLib as well. Then you can change the link from vecLib to MKL in the BLAS stub. Note that we only need the C ABI, there are wrappers vecLibg95f.* which re-map the F entry points to C entry points as to avoid Fortran ABI issues thus you don't care about the Fortran. However, historically, MKL has not been much more performant than vecLib so it's unclear if it is worth the hassle. As with any accelerated BLAS, note that this may have effects on results in R.

Cheers,
Simon



> On 28/09/2020, at 7:07 PM, rollin <rollinforall using gmail.com> wrote:
> 
> I wanted to build R from source on macos (10.15.5) so I could include
> Intel's MKL.  So I first looked at building R from source without MKL.
> 
> From the installation doc, I modified config.site to have the following:
> 
> CC=clang
> OBJC=$CC
> FC=/usr/local/bin/gfortran
> CXX=clang++
> 
> 
> I then ran configuration via the command:
> 
> ./configure -C --enable-R-shlib --enable-memory-profiling
> --x-includes=/opt/X11/include --x-libraries=/opt/X11/lib
> PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig:/usr/local/lib/pkgconfig:/usr/lib/pkgconfig
> 
> 
> And received the following information and error:
> 
> checking if bzip2 version >= 1.0.6... no
> checking whether bzip2 support suffices... configure: error: bzip2 library
> and headers are required
> 
> 
> By looking at the log, I saw a compiler error due to an implicit function.
> I then made the following change in config.site:
> 
> CFLAGS='-Wno-implicit-function-declaration -g -O2''
> 
> 
> And configure now ran without errors.
> 
> However, when I looked at configuring to use MKL, I discovered that MKL on
> macos does not support gnu fortran so, unless I purchase Intel's Fortran
> compiler, it looks like I'm sol.
> 
> Has anyone built R with MKL on macos (10.15)?  In any event, I wanted to at
> least note the issue and work around I encountered when building R on
> macos with clang/xcode.
> 
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