symmetric reordering and incomplete factorization with tolerance?

[zhifeng sheng]

Dear all

I used the reordering scheme in petsc, and I would like to know whether 
they are symmetric or not.

I have a symmetric matrix (for 3D system) and I tried to solve it with 
petsc and with matlab.

In petsc I used rcm + ILU + bicgstab. while in matlab I used 
symrcm+ICC+bicgstab.

it seems that with symmetric reordering, the factorization is somewhat 
faster... So I am wondering if it is possible to apply a symmetric 
reordering?

PS: in Matlab, an incomplete factorization can be done with a tolerance 
(e.g. ICC(1e-4) ), can I do something like that with Petsc?

Thanks a lot
Best regards
Zhifeng Sheng