This says "-openmp <num> after -parallel", this says "export ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS=2", while this says "--threads nthreads" for parallel processing. I want to run recon-all and want all processes under recon-all to be parallelized. Which one(s) of the above flags should I provide with recon-all? Please note that the values are not my interest, the flags are. I know the proper values I should choose for the flags on my machines.

So far I have been trying "-parallel -openmp 4" option only but my run time stays over 5 hours contrary to less than 3 hours stipulated in the documentation.