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 <[email protected]> > wrote: > > I am solving the isothermal form of the Navier-Korteweg system of equations - > it's mixed hyperbolic-elliptic in nature. > ------------------------------------------- > Regards > > Sthavishtha Bhopalam Rajakumar > > > > > > > On Sun, Apr 11, 2021 at 11:37 PM Matthew Knepley <[email protected] > <mailto:[email protected]>> wrote: > On Sun, Apr 11, 2021 at 1:37 PM sthavishtha bhopalam <[email protected] > <mailto:[email protected]>> 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 > > 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 > > 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. > > Hypre is only going to work for a very specific set of systems. What are you > solving? > > Thanks, > > Matt > > Thanks > ------------------------------------------- > Regards > > Sthavishtha > > > > > > > -- > 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/>
