[Trilinos-Users] Inverse of a sparse matrix

[Martin Vymazal]

Hello Mark,

  no, I'm not a physicist. My matrix is a discrete representation of  
an operator acting between two finite element grids. Wherever I could,  
I avoided the inversion by solving Ax=b. Unfortunately, now I really  
need the complete inverse.

   Best regards,

  Martin Vymazal

Quoting Mark Hoemmen <mhoemme at sandia.gov>:

> 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
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>



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