M1 Mac compile Mex file with OpenMP

I tried to compile mex function in M1 mac with matlab 2022a and matlab 2022a beta, it works well without openmp. But When I tried to include omp.h, error occurs.

Step1, I installed openmp with xcode,

curl -O https://mac.r-project.org/openmp/openmp-13.0.0-darwin21-Release.tar.gz 
sudo tar fvxz openmp-13.0.0-darwin21-Release.tar.gz -C /

test1.cpp

#include <omp.h>
#include <iostream>
 int main() {
 #pragma omp parallel
 std::cout<<"Hello from thread: "<< omp_get_thread_num()<< "nthreads: " << omp_get_num_threads() << "\n";
 }

I can compile test1.cpp with (-Xpreprocessor also works):

 clang++ -Xclang -fopenmp -lomp test1.cpp

The results looks good:

Hello from thread 0, nthreads 8
Hello from thread 2, nthreads 8
Hello from thread 4, nthreads 8
Hello from thread 3, nthreads 8
Hello from thread 5, nthreads 8
Hello from thread 7, nthreads 8
Hello from thread 1, nthreads 8
Hello from thread 6, nthreads 8

Step2, I tried to build a test function with matlab

test2.cpp

If I use #include "omp.h", I will get: error: "omp.h" file not found, therefore I used absolute path

#include "mex.h"
#include "/usr/local/include/omp.h"
void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {
   #pragma omp parallel
   mexPrintf("Hello from thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
   mexPrintf("hello world!\n");
}

mex command I used

matlab 2022a beta

mex -v CXXFLAGS='$CXXFLAGS -Xclang -fopenmp -arch arm64' LDFLAGS='$LDFLAGS -I/usr/local/include -L/usr/local/lib -lomp -mmacosx-version-min=12.4' -I'usr/local/include' -L'usr/local/lib' test2.cpp

matlab 2022a

mex -v CXXFLAGS='$CXXFLAGS -Xclang -fopenmp -arch x86_64' LDFLAGS='$LDFLAGS -I/usr/local/include -L/usr/local/lib -lomp -mmacosx-version-min=12.4' -I'usr/local/include' -L'usr/local/lib' test.cpp

MEX completed successfully, but if I run the test2.mexmaci64 or test2.mexmaca64, maltab stopped immediately.

If I commented this line,

#pragma omp parallel

The results became:

Hello from thread 0, nthreads 1
hello world!

Supported compiler on mac is Xcode 13.x and my clang --version is:

Apple clang version 13.1.6 (clang-1316.0.21.2.5)

Target: arm64-apple-darwin21.5.0

[shuang zhou]

Update:

test.cpp (absolute path of "omp.h" is not required)

#include "mex.h"
#include "omp.h"
void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {
   #pragma omp parallel
   mexPrintf("Hello from thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
   mexPrintf("hello world!\n");
}

mex command:

mex -v CXX_FLAGS="-Xclang -fopenmp" LDFLAGS="$LDFLAGS -lomp" -I/usr/local/include test.cpp

This command works with 1 thread, this mex command will generate 3 commands for clang++:

/usr/bin/xcrun -sdk macosx12.3 clang++ -c -DMATLAB_DEFAULT_RELEASE=R2017b  -DUSE_MEX_CMD   -DMATLAB_MEX_FILE  -I"/usr/local/include"  -I"/Applications/MATLAB_R2022a.app/extern/include" -I"/Applications/MATLAB_R2022a.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -O2 -fwrapv -DNDEBUG "my_path/test.cpp" -o /var/folders/36/h6gn6pqj20g79jrplzyd5y800000gn/T/mex_35678585508292_17546/test.o
/usr/bin/xcrun -sdk macosx12.3 clang++ -c -DMATLAB_DEFAULT_RELEASE=R2017b  -DUSE_MEX_CMD   -DMATLAB_MEX_FILE  -I"/usr/local/include"  -I"/Applications/MATLAB_R2022a.app/extern/include" -I"/Applications/MATLAB_R2022a.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -O2 -fwrapv -DNDEBUG "/Applications/MATLAB_R2022a.app/extern/version/cpp_mexapi_version.cpp" -o /var/folders/36/h6gn6pqj20g79jrplzyd5y800000gn/T/mex_35678585508292_17546/cpp_mexapi_version.o
/usr/bin/xcrun -sdk macosx12.3 clang++ -Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.15 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -framework Cocoa -bundle  -stdlib=libc++ -lomp -O -Wl,-exported_symbols_list,"/Applications/MATLAB_R2022a.app/extern/lib/maci64/mexFunction.map" -Wl,-exported_symbols_list,"/Applications/MATLAB_R2022a.app/extern/lib/maci64/c_exportsmexfileversion.map" -Wl,-U,_mexCreateMexFunction -Wl,-U,_mexDestroyMexFunction -Wl,-U,_mexFunctionAdapter -Wl,-exported_symbols_list,"/Applications/MATLAB_R2022a.app/extern/lib/maci64/cppMexFunction.map" /var/folders/36/h6gn6pqj20g79jrplzyd5y800000gn/T/mex_35678585508292_17546/test.o /var/folders/36/h6gn6pqj20g79jrplzyd5y800000gn/T/mex_35678585508292_17546/cpp_mexapi_version.o   -L"/Applications/MATLAB_R2022a.app/bin/maci64" -lmx -lmex -lmat -L"/Applications/MATLAB_R2022a.app/extern/bin/maci64" -lMatlabDataArray -lMatlabEngine -o test.mexmaci64

-Xclang -fopenmp did not present in these cmds, therefore the test.mexmaci64 can only use 1 thread.

If I add -fopenmp:

mex -v CXX_FLAGS="-Xclang -fopenmp" LDFLAGS="$LDFLAGS -lomp" CXXOPTIMFLAGS="$CXXOPTIMFLAGS -Xclang -fopenmp" -I/usr/local/include test.cpp

Matlab will crash when I run test().

I modified the mex derived 3 commands and find openmp in the first one will crash matlab:

/usr/bin/xcrun -sdk macosx12.3 clang++ -c -DMATLAB_DEFAULT_RELEASE=R2017b  -DUSE_MEX_CMD   -DMATLAB_MEX_FILE  -I"/usr/local/include"  -I"/Applications/MATLAB_R2022a.app/extern/include" -I"/Applications/MATLAB_R2022a.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -O2 -fwrapv -DNDEBUG -Xclang -fopenmp -lomp "my_path/test.cpp" -o /var/folders/36/h6gn6pqj20g79jrplzyd5y800000gn/T/mex_35678585508292_17546/test.o

It looks like matlab do not support openmp well, but I know matlab do support openmp with mex.

I tried a simple function test3.m

function test3(n)
parfor i = 1:n
    fprintf('i = %d \n',i);
end
end

Then use matlab coder to generate mex function, I found the cmds used in matlab coder

[1/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" /Applications/MATLAB_R2022a.app/extern/version/cpp_mexapi_version.cpp -o build/maci64/cpp_mexapi_version.o
[2/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" test3_data.cpp -o build/maci64/test3_data.o
[3/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" interface/_coder_test3_info.cpp -o build/maci64/_coder_test3_info.o
[4/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" rt_nonfinite.cpp -o build/maci64/rt_nonfinite.o
[5/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" test3_initialize.cpp -o build/maci64/test3_initialize.o
[6/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" eml_int_forloop_overflow_check.cpp -o build/maci64/eml_int_forloop_overflow_check.o
[7/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" interface/_coder_test3_mex.cpp -o build/maci64/_coder_test3_mex.o
[8/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" test3_terminate.cpp -o build/maci64/test3_terminate.o
[9/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" interface/_coder_test3_api.cpp -o build/maci64/_coder_test3_api.o
[10/11] /usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/mypath" -I "./interface" -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test3_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" test3.cpp -o build/maci64/test3.o
[11/11] /usr/bin/xcrun -sdk macosx12.3 clang++ build/maci64/test3_data.o build/maci64/rt_nonfinite.o build/maci64/test3_initialize.o build/maci64/test3_terminate.o build/maci64/test3.o build/maci64/_coder_test3_api.o build/maci64/_coder_test3_mex.o build/maci64/eml_int_forloop_overflow_check.o build/maci64/_coder_test3_info.o build/maci64/cpp_mexapi_version.o -Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.15 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -framework Cocoa -bundle -stdlib=libc++ -L"/Applications/MATLAB_R2022a.app/bin/maci64" -lmx -lmex -lmat -L"/Applications/MATLAB_R2022a.app/extern/bin/maci64" -lMatlabDataArray -lMatlabEngine -Wl,-rpath,@loader_path -o test3_mex.mexmaci64 -lemlrt -lcovrt -lut -lmwmathutil -fPIC -L"/Applications/MATLAB_R2022a.app/sys/os/maci64" -liomp5

run test3_mex(int32(16)), I got this result:

i = 15 
i = 16 
i = 11 
i = 12 
i = 13 
i = 14 
i = 9 
i = 10 
i = 1 
i = 2 
i = 7 
i = 8 
i = 5 
i = 6 
i = 3 
i = 4 

Then, I changed the path and filenames in those cmds:

system('/usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" /Applications/MATLAB_R2022a.app/extern/version/cpp_mexapi_version.cpp -o cpp_mexapi_version.o');
system('/usr/bin/xcrun -sdk macosx12.3 clang++ -fno-common -arch x86_64 -mmacosx-version-min=10.15 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -fobjc-arc -std=c++11 -stdlib=libc++ -DMATLAB_MEX_FILE -O2 -fwrapv -DNDEBUG -fvisibility=hidden -std=c++11 -I "." -I "/Applications/MATLAB_R2022a.app/extern/include" -I "." -DMODEL=test_mex -DMW_NEEDS_VERSION_H -c -fPIC -Xpreprocessor -fopenmp -I "/Applications/MATLAB_R2022a.app/toolbox/eml/externalDependency/omp/maci64/include" -DOpenMP_omp_LIBRARY="/Applications/MATLAB_R2022a.app/sys/os/maci64/libiomp5.dylib" test.cpp -o test.o');
system('/usr/bin/xcrun -sdk macosx12.3 clang++ test.o cpp_mexapi_version.o -Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.15 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -framework Cocoa -bundle -stdlib=libc++ -L"/Applications/MATLAB_R2022a.app/bin/maci64" -lmx -lmex -lmat -L"/Applications/MATLAB_R2022a.app/extern/bin/maci64" -lMatlabDataArray -lMatlabEngine -Wl,-rpath,@loader_path -o test_mex.mexmaci64 -lemlrt -lcovrt -lut -lmwmathutil -fPIC -L"/Applications/MATLAB_R2022a.app/sys/os/maci64" -liomp5');

And crashed again.

Answer 1

[shuang zhou]

The problem is caused by print out functions,

mexPrintf function, stream out function(https://www.mathworks.com/help/matlab/matlab_external/displaying-output-in-matlab-command-window.html) or even other output functions cannot be in parallel structure!!!

mexPrintf and all other memory allocate function are thread unsafe. https://www.mathworks.com/matlabcentral/answers/418782-thread-safety-of-mx-mex-functions

As mentioned in this question : https://www.mathworks.com/matlabcentral/answers/288868-matlab-crashes-using-mex-function-and-openmp

Wrong usage (this will crash):

#include "mex.h"
#include "omp.h"
void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {
    #pragma omp parallel for
    for(int p = 0; p<16; ++p){
        mexPrintf("p = %d\n",p);// output function should not in parallel structure!!
    }
}

Correct usage test1.cpp:

#include "mex.h"
#include "omp.h"
void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {
    double sum{};
    #pragma omp parallel for reduction(+: sum)
    for(int p = 0; p<100000000; ++p){
        sum += (double)(p)*(double)(p);
    }
    mexPrintf("sum = %f\n",sum);
}

Compile:

mex CXX_FLAGS="-Xclang -fopenmp" LDFLAGS="$LDFLAGS -lomp" CXXOPTIMFLAGS="$CXXOPTIMFLAGS -Xclang -fopenmp" -I/usr/local/include test1.cpp

benchmark:

tic;test1();toc;
// with openmp 0.02s @M1 pro 8 core
// without openmp 0.1s @M1 pro 8 core

In summary:

step1 install openmp, run this in terminal (https://mac.r-project.org/openmp/):

curl -O https://mac.r-project.org/openmp/openmp-13.0.0-darwin21-Release.tar.gz 
sudo tar fvxz openmp-13.0.0-darwin21-Release.tar.gz -C /

step2 compile with -Xclang -fopenmp and -lomp

mex CXX_FLAGS="-Xclang -fopenmp" LDFLAGS="$LDFLAGS -lomp" CXXOPTIMFLAGS="$CXXOPTIMFLAGS -Xclang -fopenmp" -I/usr/local/include test1.cpp

[shuang zhou]

Matlab R2022a could be not stable, sometimes openmp works, something it will crash(after installation of new toolbox). Matalab R2022a beta is stable.

Calling a magic function could stablize Matlab R2022a.

How to get a magic function:

test.m

function test(n)
parfor i = 1:n
    fprintf('i = %d \n',i);
end
end

Convert to mex function with matlab coder (input should be int32 1x1 scalar), run the mex function

test_mex(int32(n));

[shuang zhou]

the magic function can be found in my repo :https://github.com/civerjia/Proton-Bragg-Peak-Fit

go to the utils folder and run ifMacCrashed()