Number of threads

[Aratopn]

Greetings!

Can I somehow control the number of threads when running PICMI input file on my PC? As far as I understand, it uses half of the available threads by default.

Thank you for your time.

[ax3l]

Hi @Aratopn,

There are two ways to do this. Either you set the environment variable OMP_NUM_THREADS to the number of threads you prefer, or a runtime option in WarpX (AMReX).

For the latter, I just checked, and I think we forgot to add a sim.omp_threads control to Python (as we already have in ImpactX). Until we add this, you can set the env var or before the sim set this in Python:

    import amrex.space3d as amr

    verbose = True

    # add before the simulation setup
    pp_prof = amr.ParmParse("tiny_profiler")
    pp_prof.add("enabled", int(verbose))

    omp_threads = 4  # set this
    if not amr.initialized():
        if verbose:
            amr.initialize([f'amrex.omp_threads={omp_threads}', f'amrex.verbose={int(verbose_debug)}'])
        else:
            eval('amr.initialize([f"amrex.omp_threads={omp_threads}", "amrex.verbose=0"])')

But that's a bit of a hack and can by accident overwrite changed AMReX defaults that we use.

[ax3l]

Added a new control variable in #6288 in case env var is not working for you.

[ax3l]

Adding PICMI Control in #6314

[Aratopn]

Thanks for your reply. I'll try it when I have the chance.