I'm solving $Ax = b$ with PETSc, $A$ sparse and asymmetric.

I'm using BCGS or FGMRES or TFQMR as a solver, and ILU as a preconditioner. When I use 1 core, everything works as expected. But with 8 cores, no, I get -5, KSP_DIVERGED_BREAKDOWN, or maximum number of iterations exceeded.

What could be wrong? I am pretty sure my code is correct.

  • $\begingroup$ Could you post your code? $\endgroup$ May 23, 2023 at 22:56

1 Answer 1


ILU is not implemented for non-sequential matrices, see here.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.