[R-SIG-Mac] Apple Clang does support OpenMP (if libomp is available)
Balamuta, James Joseph
b@|@mut2 @end|ng |rom ||||no|@@edu
Thu Jun 6 16:11:15 CEST 2019
Greetings and Salutations Jon,
> Lack of OpenMP support in Apple’s build of Clang is cited as one reason for not using it in CRAN builds
From R 3.4.x forward, OpenMP has been enabled in CRAN builds as the toolchain is using a custom compiler.
You can see this with regard to the work done to enable OpenMP with RcppArmadillo with a configure script to detect the compiler:
> but this is only partly true: after installing libomp ***from Homebrew***, I have been adding
Unfortunately, both Xcode and Xcode CLI do not ship clang with support for OpenMP. By installing `libomp` from homebrew, the system is getting a clang-compliant OpenMP compiler from the llvm formula. To check, please see:
I wish it were the case though...
On 6/6/19, 5:43 AM, "R-SIG-Mac on behalf of Jon Clayden" <r-sig-mac-bounces using r-project.org on behalf of jon.clayden using gmail.com> wrote:
Lack of OpenMP support in Apple’s build of Clang is cited as one
reason for not using it in CRAN builds, but this is only partly true:
after installing libomp from Homebrew, I have been adding
“-Wp,-fopenmp” to CXXFLAGS and CFLAGS (and “-lomp” to LIBS) to my
builds for a while, and everything seems to work OK.
I’m not sure how far back this support goes (and I haven’t tried the
Xcode 11 tools yet), but is there any known reason not to take this
approach, and if not, would it make sense for R’s configure script to
try “-Wp,-fopenmp” when testing for OpenMP support?
All the best,
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