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I think to achieve what you want you will need to use a KSP which supports right preconditioning, that is they monitor || Ax-b || rather than || P^{-1} ( Ax - b ) ||, where P^{-1} is the application of the preconditioner. Try running with -ksp_type
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<div dir="auto">I think to achieve what you want you will need to use a KSP which supports right preconditioning, that is they monitor || Ax-b || rather than || P^{-1} ( Ax - b ) ||, where P^{-1} is the application of the preconditioner.</div><div dir="auto"><br></div><div dir="auto">Try running with -ksp_type fgmres or -ksp_type gcr. These Krylov methods support right preconditioning by default.</div><div dir="auto"><br></div><div dir="auto">Thanks,</div><div dir="auto">Dave</div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon 22. Jul 2024 at 04:37, Константин Мурусидзе <<a href="mailto:konstantin.murusidze@math.msu.ru">konstantin.murusidze@math.msu.ru</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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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,
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<div><div>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.</div></div>
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