About the basic Advection_AmrLevel test case

[paradoxknight1]

Hi,

Sorry for bothering again, this time we are trying to study the AmrLevel interface.

Here in the Test case, during my study, I found it a little difficult to understand why the ghost cell's number in Umac is defined as the number of iteration for nodal velocity, which is eventually used to evolve the flow field.

MultiFab Umac[BL_SPACEDIM];
for (int i = 0; i < BL_SPACEDIM; i++) {
    BoxArray ba = S_new.boxArray();
    ba.surroundingNodes(i);
    Umac[i].define(ba, dmap, 1, iteration);
}

from this file https://github.com/AMReX-Codes/amrex/blob/development/Tests/Amr/Advection_AmrCore/Source/AmrCoreAdv.cpp

amrex/Tests/Amr/Advection_AmrLevel/Source/AmrLevelAdv.cpp

Line 286 in 78268f1

MultiFab Umac[BL_SPACEDIM];

Looking forward to hearing from you.

[WeiqunZhang]

It's because of particles and subcycling. We use Umac to advance particles. A particle can move into ghost cells during subcycling. So we need enough ghost cells. How many we need depends on the number of iterations.

However, the code could be more efficient and clearer. Without particles, the number of ghost cells could be simply one.

[paradoxknight1]

thanks for your timely reply