Picongpu: particles filter for hdf5 plugin

[hightower8083]

Could you please confirm that the particle filters work for the HDF5 plugin output?

I was doing a simple test -- the LWFA example with added particleFilters.param, where I define a filter:

struct FunctorOnePercentParticles
{
    static constexpr char const * name = "OnePercentParticles";
    template< typename T_Rng, typename T_Particle >
    HDINLINE bool operator()(
        T_Rng & rng,
        T_Particle const & particle
    )
    {
        bool result = false;
        //if( rng() >= float_X( 0.99 ) )
        //    result = true;
        return result;
    }
};

using OnePercentParticles = generic::FreeRng<
   FunctorOnePercentParticles,
   pmacc::random::distributions::Uniform< float_X >
>;


using AllParticleFilters = MakeSeq_t<
    All,
    OnePercentParticles
>;

This is supposed to block completely the particles output (since selection is commented), but in the output with --hdf5.source 'species_all, fields_all'", all species are still present. Am I forgetting something essential to activate the filter ?

PS in the doc
https://picongpu.readthedocs.io/en/0.4.2/usage/particles.html#_CPPv3N8picongpu9particles6filter7generic7FreeRngE

there seem to be a bug in example -- rng >= float_X( 0.5 ) should be rng() >= float_X( 0.5 ), right ?

[ax3l]

You did everything correct. But if you want to output only the selected (or better say: unselected) particles, you can write: --hdf5.source 'species_OnePercentParticles,fields_all'.

That way, the filter "all" for species will not be written and only the "OnePercentParticles" filter is written (and fields).

You can also write --hdf5.source 'species_all,species_OnePercentParticles,fields_all' to write all particles in all species, all fields and also the one percent random selected particles (again).

[ax3l]

P.S.: Ouch, sorry for the typo in the example. The code for it is here. Do you want to fix it with a first pull request to dev? :)

The HDF5 plugin docs also do not really mention the syntax species_<filter> (./bin/picongpu --help would tell in your input set at least). We should probably update its manual page as well.

[hightower8083]

sure, I'll patch it -- its never too much of the glory =)

concerning _HDF5 plugin docs_, i confirm, that for a pure user, the fast use of this plugin is rather challenging since species_all and fields_all are hard to extrapolate -- I mean, one can easily guess replacing fields_all with E, B, etc (getting field names from the output opmd files), but choosing one species, e.g. e won't work without _all..

At least it getting clearer, why _Functor_ requires the name string ;-)

uod patch is https://github.com/ComputationalRadiationPhysics/picongpu/pull/2825

[ax3l]

Thx for the PR!

Docs: Yes, I wonder where we can efficiently document that. Nearly every "species" plugin supports filters now (yay!) so we can probably doc the naming convention in a common place in plugins, potentially before this section, and link in each plugin to it.

The creation of filters is, as you found, already doc-ed at least (now in the .param section)

[psychocoderHPC]

I removed my text here I posted the answer to the wrong issue.