[petsc-users] Use of PCApplyBAorAB with PC_SYMMETRIC side

[Sylvain Mercier]

Hello everyone,

I want to use PCApplyBAorAB symmetrically with a preconditioner from an ICC
factorization.
However, I don't understand why the result is not the same if I use a
natural or a RCM ordering during the factorization.
This problem does not occur if I use this routine with PC_LEFT or PC_RIGHT

I have put in attachment a code to illustrate the problem.
I compute a symmetric matix A in R^{n*n} and a full rank matrix B in R^{m*n}
I compute an ICC factorization of  the SPD matrix A+B^TB to precondition A.

Thank you!

Sylvain Mercier
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