[MacPorts] #61256: Multicore support for math/R

[MacPorts]

#61256: Multicore support for math/R
--------------------------+----------------------
  Reporter:  webbp        |      Owner:  kjellpk
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  R            |
--------------------------+----------------------

Comment (by webbp):

 {{{compiler.openmp_version 4.5}}} did not enable R to build packages with
 OpenMP, e.g., with {{{compiler.openmp_version 4.5}}}:
 {{{
 clang: error: unknown argument: '-pipe -Os
 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk -arch
 x86_64'
 *** OpenMP not supported! data.table uses OpenMP to automatically
 ***   parallelize operations like sorting, grouping, file reading, etc.
 }}}

 I've investigated the problem a bit more. The issue mostly or entirely
 affects packages installed by R rather than the R binary itself, that is,
 there are many R packages which benefit greatly from being built with
 openmp, but the R binary may not. The above .R/Makevars cause R to build
 packages with OpenMP in Mac OS 10.11, whereas these below work for 10.15.
 (Those are the only two Mac OS versions I have readily available.)
 {{{
 CC=/opt/local/bin/clang -fopenmp
 CXX=/opt/local/bin/clang++ -fopenmp
 # -O3 should be faster than -O2 (default) level optimisation ..
 CFLAGS=-isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -g
 -O3 -Wall -pedantic -std=gnu99 -mtune=native -pipe
 CCFLAGS=-isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk
 CXXFLAGS=-isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -g
 -O3 -Wall -pedantic -std=c++11 -mtune=native -pipe
 LDFLAGS=-L/opt/local/lib -Wl,-rpath,/opt/local/lib
 CPPFLAGS=-I/opt/local/include
 }}}

 Source: https://github.com/Rdatatable/data.table/wiki/Installation

 Also, I believe that R uses the flags with which it was built as the
 default flags for building packages, so specifying these flags the
 Portfile should solve the problem. However, the specific flags that work
 differ for different Mac OS versions, and they are also known to be
 incompatible with some R packages. So maybe the best thing to do here is
 just to add some lines to the Portfile long_description, e.g.: to install
 multicore packages in R, do {{{sudo port install clang-10 pkgconfig &&
 sudo port select clang mp-clang-10}}} and create ~/.R/Makevars as above.

-- 
Ticket URL: <https://trac.macports.org/ticket/61256#comment:8>
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