Diagonal Elements of an Inverse Matrix

Zhifeng Sheng z.sheng at ewi.tudelft.nl
Mon Nov 26 03:49:16 CST 2007

Tim Stitt wrote:

> 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.
There is one method call approximate schur inverse . It computes the 
exact number of inverse matrix on diagonals without knowing the number on

off-diagonal blocks.

best regards

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