[petsc-users] Using external matrix as ILU preconditioner

[Milan Pelletier]

Dear PETSc users,

I would like to know if it is possible to provide PETSc with a ILU-preconditioner matrix computed externally beforehand.
I tried and built a PCSHELL, to which I pass the externally-computed preconditioner matrix as "Pmat" using the KSPSetOperators function. Then I wanted to use that Pmat in PCApply by calling MatSolve as it seems to be done in the ILU case. Though, this fails since the mat->ops->solve (with mat being my PC Matrix) is a null pointer.

I guess the way I set the matrix (as a MATSEQAIJ) is not sufficient for PETSc to know what function to use as MatSolve.

How could I achieve providing my own ILU-decomposed matrix and feed PETSc's PCG with it? Is it actually possible?

Thanks for your help,
Milan Pelletier
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