[petsc-users] Extracting data from a Petsc matrix

[Matthew Knepley]

On Tue, Jul 16, 2013 at 1:13 PM, Harshad Sahasrabudhe
<hsahasra at purdue.edu>wrote:

> Hi Jed,
>
> Thanks for your reply.
>
>  You're on your own for storage of factors.  Alternatively, you could add
>> library support so that you could use PCLU and
>> '-pc_factor_mat_solver_package magma' (or PCFactorSetMatSolverPackage).
>> Doing this is not a priority for us, but we can provide guidance if you
>> want to tackle it.
>>
>
> I would definitely like to start working on adding library support. I
> think this is the most efficient way to go about it. Can you give me
> certain details such as:
>
> 1) How should I start going about it?
>

Read the UMFPACK implementation


> 2) How will I check-in the changes to Petsc?
>

Using Git


> 3) What version of Petsc will the changes be reflected in if I started
> working on it right now?
>

A branch of 'master'


> 4) How many hours does it generally take to get this done?
>

How many licks does it take to get to the center of a Tootsie Roll Pop?


> 5) How is the peer review done?
>

Through a pull request on BitBucket.

  Thanks,

     Matt


> Thanks,
> Harshad
>
> On 07/13/2013 12:43 PM, Jed Brown wrote:
>
>> "hsahasra at purdue.edu" <hsahasra at purdue.edu> writes:
>>
>>  Hi,
>>>
>>> I am working on solving a system of linear equations with square
>>> matrix. I'm first factoring the matrix using LU decomposition.
>>>
>> I assume you're solving a dense problem because that is all MAGMA does.
>>
>>  I want to do the LU decomposition step using MAGMA on GPUs. MAGMA
>>> library implements LAPACK functions on a CPU+GPU based system.
>>>
>>> So my question is, how do I extract the data from a Petsc Mat so that
>>> it can be sent to the dgetrf routine in MAGMA.
>>>
>> MatDenseGetArray
>>
>>  Is there any need for duplicating the data for this step?
>>>
>> You're on your own for storage of factors.  Alternatively, you could add
>> library support so that you could use PCLU and
>> '-pc_factor_mat_solver_package magma' (or PCFactorSetMatSolverPackage).
>> Doing this is not a priority for us, but we can provide guidance if you
>> want to tackle it.
>>
>
>


-- 
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
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