[petsc-users] Convergence problem in solving a symmetric positive definite matrix in a CFD code

[Jed Brown]

"Xiao, Jianjun (IKET)" <jianjun.xiao at kit.edu> writes:

> Hi Matt,
>
> I am using PETSc-dev because only this version supports
> MatSetValuesBlockedStencil in Fortran. I tried many combinations of
> KSP and PC. None of them worked in my case. The same thing happened to
> PETSc-3.4.
>
> Then I changed back to 3.3-P7 and 3.2-P7 without using
> MatSetValuesBlockedStencil. I tried KSPCR+PCBJACOBI and many others,
> they worked fine.

We're going to need exact options and output for the cases you tried.
You should be able to use the same algorithm with both versions (with
suitable options).  And if you have a modest-sized problem, you can run
with -ksp_view_mat and send binaryoutput.  We'll use
src/ksp/ksp/examples/tutorials/ex10.c to reproduce the convergence you
see.
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