Control issues in MultiApps

[Blackfoxdragon]

When using Multiapps, the executioner of one of my subapps is eigenvaule. After the variables in this app are updated, how can I restart the solver of this subapp?
In my previous calculation, the solution of this app was skipped after being solved once

[GiudGiud]

Hello

there is a parameter to reset multiapps in the Multiapps block. This is a little overkill, it will remove the solution from the subapp

you can also set a minimum number for of nonlinear iterations to force a solve in the executioner of the subapp

the better solution is to understand why the initial residual of the subapp with updated variables is still such that the solve is skipped

[GiudGiud]

once it's solved once, it won't be solved again?

If the variables are at the value that minimizes the residual, then the solve does not happen again

Are there any similar examples for learning?

Similar examples of? Eigenvalue simulations as child applications?

[Blackfoxdragon]

So, in fact, the executioner still performed the solution, but this step was no different from the previous one, so the solution was skipped?
If I change a parameter involved in the eigenvalue calculation before subapp solves at a new time step, can the calculation proceed?

[Blackfoxdragon]

Similar examples of? Eigenvalue simulations as child applications?

yes,I think need some examples like this

[GiudGiud]

I just checked and execute an eigenvalue calculation on each time step worked fine?
parent

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 10
  ny = 10
[]

[Variables]
  [./u]
  [../]
[]

[Kernels]
  [./diff]
    type = Diffusion
    variable = u
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = left
    value = 0
  [../]
  [./right]
    type = DirichletBC
    variable = u
    boundary = right
    value = 1
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 4

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
  nl_abs_tol = 1e-8

[]

[Outputs]
  exodus = true
  perf_graph = true
[]

[MultiApps]
  [full_solve]
    type = FullSolveMultiApp
    positions = '0 0 0'
    input_files = sub_eigen.i
  []
[]

[Transfers]
  [tt]
    type = MultiAppGeneralFieldShapeEvaluationTransfer
    source_variable = 'u'
    variable = 'u'
    to_multi_app = full_solve
  []
[]

Child app

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 10
  ny = 10
[]

[Variables]
  [u]
  []
[]

[Kernels]
  [diff]
    type = Diffusion
    variable = u
  []
  [rhs]
    type = MassEigenKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = DirichletBC
    variable = u
    boundary = left
    value = 0
  []
  [right]
    type = DirichletBC
    variable = u
    boundary = right
    value = 1
  []
[]

[Executioner]
  type = NonlinearEigen

  bx_norm = 'unorm'

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'

  # nl_forced_its = 4
  line_search = none

[]

[Postprocessors]
  [unorm]
    type = ElementIntegralVariablePostprocessor
    variable = u
    # execute on residual is important for nonlinear eigen solver!
    execute_on = linear
  []
[]

[Outputs]
  exodus = true
[]

[Blackfoxdragon]

Thank you! I have solved my problem. It turned out that the reason was that the nonlinear residual was set too large.