[petsc-users] BoomerAMG Hypre options

[Barry Smith]

  BoomerAMG will never simply solve the resulting linear system. Mixing elliptic and hyperbolic equations into a linear system and then trying a "black-box" solver will never work.


> On Apr 11, 2021, at 11:35 PM, sthavishtha bhopalam <sthavishthabr at gmail.com> wrote:
> 
> I am solving the isothermal form of the Navier-Korteweg system of equations - it's mixed hyperbolic-elliptic in nature.
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> Regards
> 
> Sthavishtha Bhopalam Rajakumar
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> On Sun, Apr 11, 2021 at 11:37 PM Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>> wrote:
> On Sun, Apr 11, 2021 at 1:37 PM sthavishtha bhopalam <sthavishthabr at gmail.com <mailto:sthavishthabr at gmail.com>> wrote:
> Hello PETSc users
> 
> I am trying to experiment with Hypre's BoomerAMG preconditioner which continually yields the error message "Linear solve did not converge due to DIVERGED_DTOL iterations 1". I would appreciate if someone can suggest some ways I could get BoomerAMG to yield converged results - the attached output shows a snippet of the error message. Command Line options I used for BoomerAMG : -pc_type hypre -pc_hypre_type boomeramg -pchypreboomeramgtol 1.0e-3 -pchypreboomeramgstrongthreshold 0.25 -ksp_type richardson -pc_hypre_boomeramg_max_iter 6 -snes_rtol 1.0e-3 -ksp_rtol 1.0e-3 -ksp_view -snes_view -ksp_monitor -snes_monitor -ksp_max_it 100 -ksp_converged_reason -snes_converged_reason
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> I also tried using -ksp_type gmres, different values of -pc_hypre_boomeramg_max_iter, -pchypreboomeramgstrongthreshold, -ksp_initial_guess_nonzero but all yielded the same error message.
> 
> However, the direct solver converges as required - the attached output shows a snippet of the norms from the SNES and KSP.
> Command Line options I used for the direct solver : -ksp_type gmres -pc_type lu -pc_factor_shift_type nonzero -pc_factor_mat_solver_type mumps -snes_converged_reason -ksp_converged_reason -ksp_rtol 1e-3 -snes_rtol 1e-3 -ksp_monitor -snes_monitor
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> There is no particular reason for using the AMG here, but I just wanted to familiarize with it's options to see which of them need to be particularly tuned to yield converged and correct results.
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> Hypre is only going to work for a very specific set of systems. What are you solving?
> 
>   Thanks,
> 
>      Matt
>  
> Thanks
> -------------------------------------------
> Regards
> 
> Sthavishtha 
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> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>

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