This is specific to Apple's Clang compiler. Having libomp installed allows you to compile OpenMP code, because /usr/local/include (where Homebrew symlinks omp.h) is on the compiler's include path, but you have to link the library explicitly: $ g++ -Xclang -fopenmp foo.cc -lomp I guess, when you say you 'installed OpenMP using brew' you actually mean you installed libomp using brew. This is because -Xclang -fopenmp enables processing and transformation of OpenMP pragmas, but one needs the OpenMP runtime too.įor 2, you may install libomp from Homebrew - the open-source version of Intel OpenMP runtime, which is now LLVM OpenMP runtime. But that is not enough - it will result in either the compiler failing to find omp.h or produce link errors with missing symbols.

Instead of -fopenmp, pass -Xclang -fopenmp. it doesn't directly understand the -fopenmp option, although it is listed in the output of clang -help.Modern versions of Clang do support OpenMP, and the one from Apple does too. InstalledDir: /Library/Developer/CommandLineTools/usr/bin Gcc and g++ that come with Xcode are nothing but Apple's Clang under disguise: $ g++ -versionĬonfigured with: -prefix=/Library/Developer/CommandLineTools/usr -with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/4.2.1

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