[Trilinos-Users] Inverse of a sparse matrix

[Heroux, Michael A]

Martin,

How big is your system, typically and at its largest?

Mike


On 8/31/10 1:03 PM, "Martin Vymazal" <martin.vymazal at vki.ac.be> wrote:

> 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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>> Trilinos-Users at software.sandia.gov
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>> 
>> 
> 
> 
> 
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