Generation of multiple partitions for optimization of CPUs usage

Hello,

I recently started to use LIGGGHTS.
I am trying to optimize as best as I can the script to run the model. Since some locations of the domain of the simulation are never occupied by particles, I thought to split the domain in multiple partitions, allocating less CPUs for those partitions where particles never go.

Unfortunately, I cannot figure out how to do what I have in mind.
Could anyone help me to set up properly the script to run, for example, a multi partitioned simulation with the geometry attached?
Suppose we have 64 CPUs. I would like to assign an many CPUs as I can to the volumes within the green walls.

I saw I can use the command "partition yes 1 processors" to specify the CPUs per partition and the the command-line "-partition" to split the domain in several partitions. But I do not understand how I can specify the region of space that each partition should occupy.

Thanks in advance for your help.

Matteo