Modify gmx analysis code (gmx saxs) for OpenMP acceleration

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Dear GROMACS developers,

I was using gmx saxs for structural characterization. However, the system is very big and the number of frames for analysis is large, I was therefore trying to apply OpenMP for the gmx saxs as I noticed that the current version (2022.2) does not come with OpenMP like gmx hbond does.

Since the main code for the structure factor calculation is four loops (wave vector, i, j, k and particle p), this is very suitable for OpenMP acceleration.

Here is the pseudocode of what I did:

#if GMX_OPENMP 
#pragma omp parallel default(shared) \
                         private(i, j, k,\
                         kx, ky, kz,\
                         krr, kr,\
                         p, asf, kdotx)
    /*the parallel code*/
#else
    /*the original code*/
#endif

Then I compiled it with:

make
sudo make install

However, when I run the code, it is still running the serial version, skipping the OpenMP part. I was wondering what I missed. Any suggestions or comments are highly appreciated.