For those impatient, skip to how to enable OpenMP in packages.
Apple has explicitly disabled OpenMP support in compilers that they ship in Xcode:
$ clang -c omp.c -fopenmp clang: error: unsupported option '-fopenmp'even though clang had OpenMP support for quite a long time now (great thanks to the folks at Intel providing their library as open source!). In fact, the clang compiler in Xcode can generate all the necessary code for OpenMP. It can be tricked into performing its designed function by using -Xclang -fopenmp flags.
The unfortunate part about this is that Apple is not shipping the necesssary libomp.dylib run-time library needed for OpenMP support. To make things worse, the version of the library you need depends on the clang version used, which Apple obfuscates so that it's non-trivial to reverse-engineer it. Fortunately, some clever folks were able to find the traces in Apple's released source so we can build the binaries that correspond to the clang version used. It is sometimes possible to use a more recent version of the runtime than the version of Apple clang.
curl -O https://mac.r-project.org/openmp/openmp-12.0.1-darwin20-Release.tar.gz sudo tar fvxz openmp-12.0.1-darwin20-Release.tar.gz -C /The contained set of files is the same in all tar balls:
usr/local/lib/libomp.dylib usr/local/include/ompt.h usr/local/include/omp.h usr/local/include/omp-tools.hso you can simply remove those to uninstall. Note that any package you compile against libomp.dylib will need that run-time so you have to ship it with your package or have users install it. You can verify the signature in the library via codetool (see below).
Build | Download | SHA1 checksum |
---|---|---|
LLVM 14.0.6 Xcode 14+ (Apple clang 1400.x) |
openmp-14.0.6-darwin20-Release.tar.gz (Release) openmp-14.0.6-darwin20-Debug.tar.gz (Debug) |
19912991431ecf032f037b6e8aea19dbd490f1ba 6b96a15db9329ea6f605449a630575036fa20aae |
LLVM 13.0.0 Xcode 13.3-13.4.1 (Apple clang 1316.x) |
openmp-13.0.0-darwin21-Release.tar.gz (Release) openmp-13.0.0-darwin21-Debug.tar.gz (Debug) |
47af4cb0d1f3554969f2ec9dee450d728ea30024 f6f8f1f49c02d5ec0729b56ddc7eaf51e7f04714 |
LLVM 12.0.1 Xcode 13.0-13.2.1 (Apple clang 1300.x) |
openmp-12.0.1-darwin20-Release.tar.gz (Release) openmp-12.0.1-darwin20-Debug.tar.gz (Debug) |
4fab53ccc420ab882119256470af15c210d19e5e 58b4323e7933e12cba5c2996b4c9ef27567c41d9 |
LLVM 11.0.1 (+M1 patch) Xcode 12.5 (Apple clang 1205.x) |
openmp-11.0.1-darwin20-Release.tar.gz (Release) openmp-11.0.1-darwin20-Debug.tar.gz (Debug) |
0dcd19042f01c4f552914e2cf7a53186de397aa1 65e83ea667c72bbe44fea699776564d2f03a080f |
LLVM 10.0.0 Xcode 12.0-12.4 (Apple clang 1200.x) |
openmp-10.0.0-darwin17-Release.tar.gz (Release) openmp-10.0.0-darwin17-Debug.tar.gz (Debug) |
9bf16a64ab747528c5de7005a1ea1a9e318b3cf0 d4508d3f0c2952c3f984393b088e0b4beab33b58 |
LLVM 9.0.1 Xcode 11.4-11.7 (Apple clang 1103.x) |
openmp-9.0.1-darwin17-Release.tar.gz (Release) openmp-9.0.1-darwin17-Debug.tar.gz (Debug) |
e5bd8501a3f957b4babe27b0a266d4fa15dbc23f c4c8491631504fb060f7c25ec14324d02d617d5b |
LLVM 8.0.1 Xcode 11.0-11.3.1 (Apple clang 1100.x) |
openmp-8.0.1-darwin17-Release.tar.gz (Release) openmp-8.0.1-darwin17-Debug.tar.gz (Debug) |
e4612bfcb1bf520bf22844f7db764cadb7577c28 d6c83918b28405d43950d4b864ca8d1687eed4d1 |
LLVM 7.1.0 Xcode 10.2-10.3 (Apple clang 1001.x) |
openmp-7.1.0-darwin17-Release.tar.gz (Release) openmp-7.1.0-darwin17-Debug.tar.gz (Debug) |
6891ff6f83f2ed83eeed42160de819b50cf643cd 34456adde62b9a1047f906e1d7f54990a1c15a34 |
PKG_CPPFLAGS='-Xclang -fopenmp' PKG_LIBS=-lomp R CMD INSTALL myPackageIf that doesn't work, please consult the package's documentation, and liaise with its maintainer. It is also possible to add those flags globally by adding the following to ~/.R/Makevars:
CPPFLAGS += -Xclang -fopenmp LDFLAGS += -lompbut be very careful when doing this, always check your ~/.R/Makevars whenever you upgrade R, macOS or Xcode.
$ codesign -d -vv /usr/local/lib/libomp.dylib Executable=/usr/local/lib/libomp.dylib Identifier=libomp Format=Mach-O universal (x86_64 arm64) CodeDirectory v=20400 size=5514 flags=0x0(none) hashes=167+2 location=embedded Signature size=8927 Authority=Developer ID Application: Simon Urbanek (VZLD955F6P) Authority=Developer ID Certification Authority Authority=Apple Root CA Timestamp=11/11/2021 at 1:29:04 PM Info.plist=not bound TeamIdentifier=VZLD955F6P Sealed Resources=none Internal requirements count=1 size=168
Last modified on 2023/02/06 by Simon Urbanek