[petsc-users] LU vs. ILU

[Hong Zhang]

Verena:

> I am somehow confused with the usage of PCLU and PCILU ind PETSc.
> It seems as there are the same options to choose from for both.
> In particular, if I use PCLU and PCFactorSetFill(pc,5)
> don't I end up with an incomplete LU factorization?

No. When user-provided fill is not sufficient, petsc will
increases it to whatever LU requires and run LU factorization.
In this case, few or more malloc() will be called, which could be
expensive.

> If I use PCLU with no other options set, will the
> factorization be complete?

Yes, be complete. But providing a good estimates for options
will make computation efficient.

Hong