I am currently studying to become a computer engineer and I need to work with OpenMP. After some research, I'm still having trouble installing it (#include <omp.h> is still not recognized). I tried libomp and llvm (with Homebrew), but I must have made a mistake along the way. Has anyone been able to use OpenMP on mac M1?
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most libraries are split into two packages. The normal runtime library in one, and the headers in a separate dev or devel package. For development you need both.stark– stark2022-02-10 12:53:35 +00:00Commented Feb 10, 2022 at 12:53
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4 Answers
On macOS 13.2.1 and up-to-date Xcode command line toolset, on M2 chip I'm able to use OpenMP based on libomp from Homebrew (brew install libomp) BUT with the Apple provided clang, by running:
clang -Xclang -fopenmp -L/opt/homebrew/opt/libomp/lib -I/opt/homebrew/opt/libomp/include -lomp omptest.c -o omptest
Where omptest.c is given as:
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv[])
{
// Beginning of parallel region
#pragma omp parallel
{
printf("Hello World... from thread = %d\n",
omp_get_thread_num());
}
// Ending of parallel region
}
Summing up, if you don't like, you don't need to install full LLVM or GCC from Homebrew. Only libomp is needed and you should be good to go!
PS. The output of running omptest on my machine (M2 Max) is:
./omptest
Hello World... from thread = 0
Hello World... from thread = 8
Hello World... from thread = 4
Hello World... from thread = 2
Hello World... from thread = 3
Hello World... from thread = 11
Hello World... from thread = 1
Hello World... from thread = 10
Hello World... from thread = 7
Hello World... from thread = 9
Hello World... from thread = 6
Hello World... from thread = 5
1 Comment
Leo
Finally an answer that worked for me. Thank you, Witwold! (I have the M1 chip)
I know this is an older thread, but this is what worked for me on an M2 MacBook Pro using C++, and g++-12:
Install Brew: https://brew.sh/
Once Brew is installed, install GCC with the following Terminal command:
brew install gccOnce GCC is installed, use the following command make your system aware of the GCC stuff, keeping in mind the
12.2.0folder may change as time goes on:PATH=/opt/homebrew/Cellar/gcc/12.2.0/bin:$PATH
I found I had to append the actual GCC file path for it to work. For some reason, it didn't add any aliases/symlinks to /usr/local/bin like it did on my older Intel MacBook Pro.
And that should be all you need! For compiling C++ code with OpenMP:
g++-12 -fopenmp progName.cpp -o prog
Note that the g++ part of the command will change with time. So check what version of g++ is installed with Brew. if the version changes from 12, then change the part of the Terminal command (e.g. g++-13, or something like that).
Hope this helps someone out!
2 Comments
Daniel
Currently working with c++ on apple m2! Thanks a lot!
CodeMonkey
It's worth noting if your brew path isn't the default and it has to build from source the brew step here takes many hours. There's nothing wrong with your machine, it's just painfully slow.
A simple approach is to use brew https://brew.sh/ to install GCC or LLVM (clang), and then use that compiler. You need to tread carefully, though, since the MacOS environment includes X86 emulation which can be confusing.
https://cpufun.substack.com/p/setting-up-the-apple-m1-for-native might help, though it's now nearly a year old...
10 Comments
ThéoS
I forgot to mention it but when I tried to install libomp and llvm I did it using homebrew. They are installed fine but impossible to import omp.h. I can compile any kind of file in C but not with this library
Jim Cownie
If you install LLVM you should not need to separately install libomp. Are you completely sure that you are using the brew-installed clang? The Apple development environment also includes an alias that means it can appear as clang too... (You might also find the hack at the end of stackoverflow.com/questions/65293299/… useful)
ThéoS
I have recently after several tests launched this command: "clang -Xpreprocessor -v -fopenmp fichier.c -lomp" and only -lomp could not be executed. I think that the post you sent me must contain the solution to my problem but I don't have the necessary knowledge to solve this problem. Is a flag, is a link that allows us to find some missing library at the origin. And yes it is clear that I must have problems between the clang provided by apple and that installed via homebrew.
Jim Cownie
First, work out which clang you are executing,
% which clang. If it's not the brew installed one, then fix your PATH so that it is and try again.ThéoS
theosouchon@MacBook-Pro-de-Theo ~ % which clang /opt/homebrew/opt/llvm/bin/clang
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M1 chip seems doesn't install llvm in the proper location.
brew install llvm
cd /opt/homebrew/opt/libomp/lib
if libomp.dylib is in the folder /opt/homebrew/opt/libomp/lib:
cd /usr/local/lib
sudo ln -s /opt/homebrew/opt/libomp/lib/libomp.dylib libomp.dylib
2 Comments
Hans Bambel
This does link the correct file, but I now get the following error from LightGBM (that wants to use libomp.dylib:
'/usr/local/lib/libomp.dylib' (mach-o file, but is an incompatible architecture (have 'arm64', need 'x86_64')). Just linking the file does not seem to fix it.
Martin Bucher
this doesn't do the job on my side sadly :(