Hi Alex,

I have had a quick look, the output you are reporting is generated by a call to EquationSystem::PrintSummary which then calls v_GenerateSummary. The function is only called if rank == 0. So, I am not sure why you would see different behaviour for MPI or serial execution.

If you are keen to take a look yourself. The parent function is in library/SolverUtils/EquationSystem.cpp::GenerateSummary and for the VelocityCorrectionScheme you would have virtual calls from child to parent in the files:

Could you share the session file for your case? (without the .xml ending as outlook filters those)

Best wishes,
Henrik
Von: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> im Auftrag von Alexander Schukmann <alexander.schukmann@protonmail.com>
Gesendet: Dienstag, 27. August 2024 18:02
An: nektar-users@imperial.ac.uk <nektar-users@imperial.ac.uk>
Betreff: [Nektar-users] Bug in IncNavierStokes solver terminal output for SVV with MPI
 

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Hello everyone,

I noticed some odd behavior of the IncNavierStokesSolvers terminal output regarding SVV when using MPI for Quasi-3D cases. When I try to use SVV in the spectral/hp planes only, i.e. without SVV along the homogeneous direction, the terminal output sometimes includes the SVV-Homo1D info, eventhough it's not specified under the SOLVERINFO tag in the session file! 
When I re-run the same case, it will randomly disappear as you can see here for two consecutive runs with identical settings:

nektar@0d6fdc64e227:~/host_pwd/run$ mpirun -n 16 IncNavierStokesSolver mesh.xml session.xml
=======================================================================
       EquationType: UnsteadyNavierStokes
       Session Name: CylReD3900_quad_coarse2_Pgeo3
       Spatial Dim.: 3
 Max SEM Exp. Order: 4
     Num. Processes: 16
           Quasi-3D: Homogeneous in z-direction
     Expansion Dim.: 3
Num. Hom. Modes (z): 64
   Hom. length (LZ): 3.14159
           FFT Type: FFTW
    Projection Type: Continuous Galerkin
Advect. advancement: explicit
Diffuse. advancement: implicit
          Time Step: 0.004
       No. of Steps: 1
Checkpoints (steps): 1
   Integration Type: IMEX
   Splitting Scheme: Velocity correction (strong press. form)
         Dealiasing: Homogeneous1D + spectral/hp
   Smoothing-SpecHP: SVV (spectral/hp DG Kernel (diff coeff = 0.10000000000000001*Uh/p))
=======================================================================

nektar@0d6fdc64e227:~/host_pwd/run$ mpirun -n 16 IncNavierStokesSolver -f mesh.xml session.xml
=======================================================================
       EquationType: UnsteadyNavierStokes
       Session Name: CylReD3900_quad_coarse2_Pgeo3
       Spatial Dim.: 3
 Max SEM Exp. Order: 4
     Num. Processes: 16
           Quasi-3D: Homogeneous in z-direction
     Expansion Dim.: 3
Num. Hom. Modes (z): 64
   Hom. length (LZ): 3.14159
           FFT Type: FFTW
    Projection Type: Continuous Galerkin
Advect. advancement: explicit
Diffuse. advancement: implicit
          Time Step: 0.004
       No. of Steps: 1
Checkpoints (steps): 1
   Integration Type: IMEX
   Splitting Scheme: Velocity correction (strong press. form)
         Dealiasing: Homogeneous1D + spectral/hp
   Smoothing-SpecHP: SVV (spectral/hp DG Kernel (diff coeff = 0.10000000000000001*Uh/p))
   Smoothing-Homo1D: SVV (Homogeneous1D - Exp Kernel(cut-off = 0.75, diff coeff = 0.10000000000000001))
=======================================================================

The first run does not output the "Smoothing-Homo1D" info, while the second one includes it, which makes it impossible to know whether it is activated or not. It'll use the SVV parameters that are set for the spectral/hp SVV if no parameters for the Homo1D-SVV are specified under the PARAMETERS tag. Otherwise the values will be overwritten, eventhough - as I said before - the feature is turned off under the SOLVERINFO tag.

Running on one CPU shows the expected behavior.

So it would be interesting to know whether this only concerns the terminal output or if the feature really is activated despite not being defined by the user.

All the best
Alex

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