How to manage CPU in parallel when there are two or more multiapps

[lvkas521424]

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Question

Hello,
After solving the parallelization problem for one multiapp, I'm trying to run a coupled multiphysics calculation involving two multiapps, each executing sequentially until convergence. I'm having some trouble.
In my program design, multiapp-1 has a large computational workload, so I want to use it for multi-core parallel computing. However, multiapp-2 has a limited functionality, so I only want it to run on a single core. I thought that could achieve this by using the "max_procs_per_app" keyword. But multiapp-2 setting max_procs_per_app to 1, results is in an error when running it with ./mpirun -n 8.
How should I set the parameters to achieve this? These two similar questions don't seem to directly address my problem.#31372 #30907

[GiudGiud]

Hello

Are they nested?
Is there a parent app, a child app and a grand child app?
Parent + Child=multiapp1 Grandchild=multiapp2 should work
but so should Parent Child1=multiap1 Child2=multiapp2

What error do you get?

[GiudGiud]

and can you please paste the multiapps block

[lvkas521424]

Hello

There all are child apps, they both belong to the same parent application. In my understanding, the parent app is just main app. There will be no nesting between them at present designing.
There are my multiapps block
The error is :

When I set max_procs_per_app = 1 for a multi app , running mpirun-n 4 will remind me that the maximum number of cores should not exceed 1. Besides, my Moose version is still stuck in the May 2024 version. Is this related to it

[MultiApps]
  [neutronics]
    type = NeutronicsMultiApp
    app_type = MooseprojectsApp
    input_files = 'scapn_input.i'
    mesh_dims = '3 4 5'          
    power_var_name1 = power_density
    power_var_name2 = tempe_density 
    temperature_var_name = temperature  
    execute_on = 'NEUTRONIC PRENEUTRONIC CORNEUTRONIC'
    
    # MPI setting
    # max_procs_per_app = 20          # max process
    min_procs_per_app = 4             # min process
    
    # execute_on = 'MULTIAPP_FIXED_POINT_BEGIN' 
  []
  
  [thermal]
    type = ThermalMultiApp
    app_type = MooseprojectsApp
    input_files = 'thermal_input.i'
    mesh_dims = '3 4 5'           
    power_var_name = power_density  
    temperature_var_name = temperature  
    execute_on = 'THERMAL'      
      
    # execute_on = 'MULTIAPP_FIXED_POINT_BEGIN'
    max_procs_per_app = 1          # max process
    # min_procs_per_app = 1           # min process
  []
[]

[GiudGiud]

what error do you get?
min_procs_per_app is generally not necessary. It will use min(max_procs_per_app, current #procs)

[lvkas521424]

I'm sorry, just after your reminder, I found through investigation that it seems to be a problem with the syntax I wrote internally in my multiapp, rather than the Moose framework