[petsc-users] RCM for ILU?

Jed Brown jed at jedbrown.org
Tue Feb 18 10:11:44 CST 2014

Qin Lu <lu_qin_2000 at yahoo.com> writes:

> RCM did not help much for my case. This case represents some strong
> connectivities in channels. I am wondering if PETSc has some
> reordering algorithm or solver that is not based on connectivity
> graph, but is based on connectivity strength (such as percolation type
> of reordering). Any information is appreciated.    Thanks, Qin

There isn't such an ordering, but it would be a welcome contribution.
One challenge is that features like anisotropy are not necessarily
apparent in the matrix entries.  In that case, and for vector-valued
problems, you would ideally use a better strength-of-connection measure.
If you computed a strength-of-connection, then thresholded (or used edge
weights as a "priority"), followed by something like an RCM ordering,
you could find something good for low-fill incomplete factorization in
problems with hidden anisotropy.
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