[petsc-users] Extracting data from a Petsc matrix

[Harshad Sahasrabudhe]

Hi Jed,

I am now working to add library support for LU decomposition using MAGMA. I need your help with the following:

1) How do I add the options --download-magma, --with-magma, etc. to the configure script for building with MAGMA?

2) I have a fair idea how the PETSc code is structured and how to add source code to the impls/ directory. How does PETSc get to know that there is an additional implementation (in this case MAGMA) in this directory? Is there a config file of some sort?

Thanks,
Harshad

----- Original Message -----
From: "Jed Brown" <jedbrown at mcs.anl.gov>
To: hsahasra at purdue.edu, petsc-users at mcs.anl.gov
Sent: Saturday, July 13, 2013 12:43:08 PM
Subject: Re: [petsc-users] Extracting data from a Petsc matrix

"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.