spectralDiffusionGreens.i

[Mesh]
  type = MyTRIMMesh
  dim = 2
  xmax = 100.0
  ymax = 100.0
  nx = 2000
  ny = 2000
[]

[Problem]
  type = FFTProblem
[]

[AuxVariables]
  [./u_aux]
    order = CONSTANT
    family = MONOMIAL
    [./InitialCondition]
      type = SmoothCircleIC
      x1 = 50
      y1 = 50
      radius = 10
      int_width = 1
      invalue = 1
      outvalue = 0.0001
    [../]
  [../]

  [./greens]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[UserObjects]
  # Buffers
  [./u]
    type = RealFFTWBuffer
    moose_variable = u_aux
  [../]
  [./greens_buffer]
    type = RealFFTWBuffer
    moose_variable = greens
  [../]

[]

[AuxKernels]
  [./u_aux]
    type = FFTBufferAux
    variable = u_aux
    fft_buffer = u
    execute_on = final
  [../]

  [./greens_aux]
    type = FFTBufferAux
    variable = greens
    fft_buffer = greens_buffer
    execute_on = final
  [../]
[]

[Executioner]
  type = SpectralExecutionerDiffusion

  # Parameters for diffusion executioner
  diffusion_coefficient = 400.0

  time_step = 0.005
  number_steps = 20
[]

[VectorPostprocessors]
  [./linevalue]
    type = LineValueSampler
    variable = 'u_aux'
    start_point = '0 50 0'
    end_point = '99.999999999 50 0'
    num_points = 101
    sort_by = x
    execute_on = final
  [../]
[]

[Outputs]
  exodus = true
  execute_on = 'INITIAL FINAL'
  perf_graph = true
  [./comp]
    type = CSV
  [../]
[]