What topology is used when julia is launched with the -p option

What topology is used when julia is launched with the -p option.
E. g. “julia somescript.jl -p 100” Is it all to all or master-slave?
In case it is not master-slave, is there a way to make it master-slave?

It is :all_to_all, by default [ref].

Yes, you can make it :master_slave [ref].

Sure, you need to change slightly the way you run your code. You simply start julia, and instide your somescript.jl, you addprocs with the corresponding topology.