Diagonal Elements of an Inverse Matrix

[Tim Stitt]

Hi PETSc Users/Developers,

I was just wondering if anyone knew of any O(N) methods for obtaining 
the diagonal elements of the inverse of a block tridiagonal 
matrix,without computing all the off-diagonal values at the same time?

Actually, the general case would be most useful were selected elements 
in the inverse could be obtained in O(N) time.

I would be grateful if anyone could shed any light on this...

Thanks,

Tim.

-- 
Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
HPC Application Consultant - ICHEC (www.ichec.ie)

Dublin Institute for Advanced Studies
5 Merrion Square - Dublin 2 - Ireland

+353-1-6621333 (tel) / +353-1-6621477 (fax)