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After this procedure I saw "Linear solution did not converge due to DIVERGED_INDEFINITE_MAT". Then as shown on https://petsc.org/main/manualpages/KSP/KSP_DIVERGED_INDEFINITE_PC/ I wrote such line PetscCall(PCFactorSetShiftType(pc, MAT_SHIFT_POSITIVE_DEFINITE)); but nothing changed and I still have divergence
22.07.2024, 17:22, "Barry Smith" <[email protected]>:
Run with -ksp_monitor_true_residual -ksp_converged_reason -ksp_view to see why it is stopping at 38 iterations.BarryOn Jul 22, 2024, at 7:37 AM, Константин Мурусидзе <[email protected]> wrote:This Message Is From an External SenderThis message came from outside your organization.Good afternoon. I am a student at the Faculty of Mathematics and for my course work I need to solve SLAE with a relative accuracy of 1e-8 or more. To do this, I created the function PetscCall(KSPSetTolerances(ksp, 1.e-8, PETSC_DEFAULT, PETSC_DEFAULT, 100000));. But in the end, only 38 iterations were made and the relative norm ||Ax-b||/||b|| it turns out 4.54011. If you reply to my email, I can give you more information about the solver settings.
