[petsc-users] issues with VecSetValues in petsc 3.19

[Edoardo alinovi]

Hello Barry,

Welcome to the party! Thank you guys for your precious suggestions, they
are really helpful!

It's been a while since I am messing around and I have tested many
combinations. Schur + selfp is the best preconditioner, it converges within
5 iters using gmres for inner solvers but it is not very fast and sometimes
multiplicative it's a better option as the inner iterations looks lighter.
If I tune the relative tolerance I get a huge speed up, but I am a bit less
confident about the results. The funny thing is that the default relative
tolerance if commercial CFD solver is huge, very often 0.1 -.-

If I may borrow your brain guys for a while, I would like to ask your
opinion about the multigrid they use in this paper:
https://www.aub.edu.lb/msfea/research/Documents/CFD-P18.pdf.
At some point they say: " The algorithm used in this work is a combination
of the ILU(0) [28] algorithm with an additive corrective multigrid method
[29] ", 29: https://www.tandfonline.com/doi/abs/10.1080/10407788608913491

Is that something similar to fieldsplit additive?

Many thanks
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