[petsc-users] iterative solvers

[Manav Bhatia]

Hi,

   I am solving a transonic Euler flow problem discretized with SUPG. The mesh is made of Tet4 elements and there are about 7M dofs, which I am trying to solve over 192 cores. 

   I had earlier written about the linear solver returning with Inf, and have since moved beyond that such that I am able to get a solution with the following command line parameters:

-ksp_gmres_restart 100  -pc_type asm -sub_pc_type ilu -sub_pc_factor_levels 4 -sub_ksp_type preonly

   The problem now is that I am limited to very small time-steps (~10e-6), outside of which the solver starts to choke and the solution diverges. I have tried other command line options and this above combination is what seems to provide the best possible solution strategy, albeit constrained in time steps. 

    I would appreciate any recommendations on solver configurations that may allow me to take larger time-steps. 

    Would coding up AMG be a possible alternative (more robust and dependable)? 

    Please let me know if you need additional information. 

Regards,
Manav

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