How do I use Particle::ParIter to iterate over multiple spheres, where each sphere is surrounded by multiple particles?

[APTX-4869-core]

Hello AMReX Team!

Regarding of the Particle class, I have some questions:

1. Assuming there's a sphere, I'm now using a new class K to represent the center of the sphere, and Particle class to represent the points surrounding the center. But I didn't create MPI means for the class K. So if I have many spheres in the domain, for getting parallel performance, should I change the usage of Particle class and the K class I created? Such as use the Particle class to represent the center, and the new K class to represent the points surrounding the sphere center?
2. Does the Redistribute() function change the address in the memory of every particle? Since I need the value of previous time step of every particle, if the address is changed, it seems hard to track the same particle.

Thanks in advance!

[atmyers]

A way people have done this is to use an AMReX to represent to center of the sphere, and then give the particle enough internal data components to reconstruct all the surrounding points.

Redistribute() does in general change the memory addresses. You could also add an additional data component to track the old value, which would then be moved around with the particle during a Redistribute().

[APTX-4869-core]

Thanks for your advice! It seems I'd better exchange the usage of these two class, and instead of modifying the original Particle class.
Another thing I want to know, is there any member variable, like particle's id that is unique for every single particle, in the Particle class? I can also track the same particle via this kind of variable.

[AlexanderSinn]

Yes, there are the particle id() and cpu() member variables. The combination of which should be unique, so long as they were set properly when the particles were initialized. Both are stored in the same 64-bit integer called idcpu(). See the (recently updated) documentation here https://amrex-codes.github.io/amrex/docs_html/Particle.html#the-particle.

[APTX-4869-core]

Thank you so much, Andrew and Alexander!