[petsc-users] Question about linking LAPACK library

[Barry Smith]

   LAPACK is always linked with PETSc so you can always make direct calls to LAPACK routines from PETSc code..

   Barry


> On Apr 25, 2023, at 6:03 AM, ­권승리 / 학생 / 항공우주공학과 <ksl7912 at snu.ac.kr> wrote:
> 
> Thank you for your reply.
> 
> I think I gave an example of an unrealistic problem.
> 
> I just wanted to know how to compute the inverse matrix, so I was wondering if there is an example of computing the inverse matrix in PETSc.
> 
> Alternatively, I want to know how to link the LAPACK library.
> 
> best,
> 
> Seung Lee Kwon
> 
> 2023년 4월 25일 (화) 오후 6:44, Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>>님이 작성:
>> On Mon, Apr 24, 2023 at 11:47 PM ­권승리 / 학생 / 항공우주공학과 <ksl7912 at snu.ac.kr <mailto:ksl7912 at snu.ac.kr>> wrote:
>>> Dear all
>>> 
>>> It depends on the problem. It can have hundreds of thousands of degrees of freedom.
>> 
>> Suppose your matrix was dense and had 1e6 dofs. The work to invert a matrix is O(N^3) with a small
>> constant, so it would take 1e18 = 1 exaflop to invert this matrix and about 10 Terabytes of RAM to store
>> it. Is this available to you? PETSc's supports Elemental and SCALAPACK for this kind of calculation.
>> 
>> If the system is sparse, you could invert it using MUMPS, SuperLU_dist, or Pardiso. Then the work and
>> storage depend on the density. There are good estimates for connectivity based on regular grids of given
>> dimension. The limiting resource here is usually memory, which motivates people to try iterative methods.
>> The convergence of iterative methods depend on detailed properties of your system, like the operator spectrum.
>> 
>>   Thanks,
>> 
>>      Matt
>>  
>>> best,
>>> 
>>> Seung Lee Kwon
>>> 
>>> 2023년 4월 25일 (화) 오후 12:32, Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>>님이 작성:
>>>> 
>>>>   How large are the dense matrices you would like to invert?
>>>> 
>>>>> On Apr 24, 2023, at 11:27 PM, ­권승리 / 학생 / 항공우주공학과 <ksl7912 at snu.ac.kr <mailto:ksl7912 at snu.ac.kr>> wrote:
>>>>> 
>>>>> Dear all
>>>>> 
>>>>> Hello.
>>>>> I want to make an inverse matrix like inv(A) in MATLAB.
>>>>> 
>>>>> Are there some methods to inverse matrix in petsc?
>>>>> 
>>>>> If not, I want to use the inverse function in the LAPACK library.
>>>>> 
>>>>> Then, how to use the LAPACK library in petsc? I use the C language.
>>>>> 
>>>>> Best,
>>>>> 
>>>>> Seung Lee Kwon
>>>>> 
>>>>> -- 
>>>>> Seung Lee Kwon, Ph.D.Candidate
>>>>> Aerospace Structures and Materials Laboratory
>>>>> Department of Mechanical and Aerospace Engineering
>>>>> Seoul National University
>>>>> Building 300 Rm 503, Gwanak-ro 1, Gwanak-gu, Seoul, South Korea, 08826
>>>>> E-mail : ksl7912 at snu.ac.kr <mailto:ksl7912 at snu.ac.kr>
>>>>> Office : +82-2-880-7389
>>>>> C. P : +82-10-4695-1062
>>>> 
>>> 
>>> 
>>> -- 
>>> Seung Lee Kwon, Ph.D.Candidate
>>> Aerospace Structures and Materials Laboratory
>>> Department of Mechanical and Aerospace Engineering
>>> Seoul National University
>>> Building 300 Rm 503, Gwanak-ro 1, Gwanak-gu, Seoul, South Korea, 08826
>>> E-mail : ksl7912 at snu.ac.kr <mailto:ksl7912 at snu.ac.kr>
>>> Office : +82-2-880-7389
>>> C. P : +82-10-4695-1062
>> 
>> 
>> -- 
>> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
>> -- Norbert Wiener
>> 
>> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
> 
> 
> -- 
> Seung Lee Kwon, Ph.D.Candidate
> Aerospace Structures and Materials Laboratory
> Department of Mechanical and Aerospace Engineering
> Seoul National University
> Building 300 Rm 503, Gwanak-ro 1, Gwanak-gu, Seoul, South Korea, 08826
> E-mail : ksl7912 at snu.ac.kr <mailto:ksl7912 at snu.ac.kr>
> Office : +82-2-880-7389
> C. P : +82-10-4695-1062

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