Named Particle SoA Components

[ax3l]

X-ref:

• Pandas: ParticleContainer_*.to_df() pyamrex#220
• Helpers: to_numpy/cupy pyamrex#88

It would be nice if AMReX supported the functionality to name particle attributes (as strings). In WarpX, we added this as NamedParticleContainer, but as a mainstream implementation we could avoid deriving yet another class type (because if we do, we will again have additional compile-time to bind that custom type in pyAMReX), and instead could just extend the particle classes with these runtime details.

[ax3l]

@atmyers volunteered to take this on 🙏 We decided to only add naming arrays for SoA (compile-time and runtime) particle components.

Examples

Here is an example of methods that we will need from ImpactX:

• Improve the Handling of Runtime Arguments ECP-WarpX/impactx#567
• Named SoA: Check and Index Getter ECP-WarpX/impactx#571

WarpX uses this earlier implementation:

• https://github.com/ECP-WarpX/WarpX/blob/24.03/Source/Particles/NamedComponentParticleContainer.H

Performance Note

Please also add two signature of the form

AddRealComp(name, comm);
AddRealComp({name1, name2, ...}, {comm1, comm2, comm3}); // or as pairs?

so people can avoid double resizes (#3615 #3861). (Same for Int.)

Deprecation

Please mark the old signature (w/o names) as deprecated - everyone can use the new signature without a problem: even if they do not use the name, this will make code more self-describing.

Default Names

As default names for the compile-time components and old Add..Comp signatures, I suggest to use the same naming scheme as in https://github.com/AMReX-Codes/pyamrex/blob/development/src/amrex/extensions/StructOfArrays.py

Tests

Currently, there are no systematic tests in AMReX CI that add (and remove #3595) runtime components to containers and then use these containers (e.g., copy from, redistribute, etc.). Such tests need to be added to ensure correctness and stability.

We currently do not cover the case where we add runtime components before the dummy multifab has been defined.