cell numbe calculation r of computational domain with refinement

[QB-Lin]

Now I have a computational domain with 2400 m (x), 1664 m (y), 960 m (z), and the volume is 3833856000 m^3.
There was 150 mesh in x direction, 104 mesh in y direction, and 60 mesh in z direction. If not refined, the cell number is 936000.
The domain have 3 nested refined region. Their size is
Level 1: 900 m900 m450 m, Volume is 472477696 m^3, cell number is 922808.
Level 2: 780 m780 m390 m, Volume is 266368512 m^3, cell number is 4162008.
Level 3: 660 m660 m330 m, Volume is 155371840 m^3, cell number is 19421480.

I hope to calculate the total mesh number in the computational domain
In the running log file of amrwind, I saw that
"
Grid summary:
Level 0 80 grids 936000 cells 100 % of domain
smallest grid: 30 x 24 x 12 biggest grid: 30 x 32 x 16
Level 1 75 grids 1115400 cells 14.89583333 % of domain
smallest grid: 26 x 26 x 22 biggest grid: 26 x 26 x 22
Level 2 196 grids 4674600 cells 7.803485577 % of domain
smallest grid: 30 x 30 x 26 biggest grid: 30 x 30 x 28
Level 3 726 grids 20830584 cells 4.346659655 % of domain
smallest grid: 30 x 30 x 28 biggest grid: 32 x 32 x 30
"
Is the total cell number = 936000 * (1 - 472477696 / 3833856000 )+ 922808 * (1- 266368512 / 472477696) + 4162008 * (1- 155371840 / 266368512) + 19421480 = 22379009?

Besides, the Grid summary said that the Level 2 is 4674600 cells. But the cell size of level 2 is 4 m, and I calculated the cell number is based on the refined region size and cell size is 3707438. Why there is a slight increase? Each refined level has this issue.

[hgopalan]

This is related to how AMReX creates tagged cells. Check documentation here: https://amrex-codes.github.io/amrex/docs_html/GridCreation.html

You can control the variables amr.grid_eff and amr.n_error_buf to force to the exact number y you want.