[Trilinos-Users] Inverse of a sparse matrix

[Mark Hoemmen]

On Aug 31, 2010, at 10:47 AM, trilinos-users-request at software.sandia.gov wrote:
> Message: 1
> Date: Tue, 31 Aug 2010 00:29:43 +0200
> From: "Martin Vymazal" <martin.vymazal at vki.ac.be>
> Subject: [Trilinos-Users] Inverse of a sparse matrix?
> To: trilinos-users at software.sandia.gov
> Message-ID: <20100831002943.122974kkn7rtlwif at horde.vki.ac.be>
> Content-Type: text/plain; charset=iso-8859-1; DelSp=Yes; format=flowed
> 
> Hello,
> 
>  I'm sorry if this question was already answered somewhere, but I
> searched and didn't find the answer. I'd like to ask what is the best
> way to compute an inverse of a Epetra__FECrsMatrix. Thank you.

Are you a physicist, and if so, do you wish to compute specific elements of the inverse?  If you are just solving linear systems Ax=b, you never want the inverse.  However, some physics applications do call for certain elements of the inverse.  If you only need, say, the diagonal entries of the inverse, there are less computationally expensive ways to do this than to compute the full inverse.

mfh