[petsc-users] Simple question regarding dense matrix algebra using elemental

[Preyas Shah]

Another beginner's querry:

​I worked out an example that "combines"
mat/examples/tests/ex145.c
 /ksp/ksp/examples/tutorials/ex2.c
/ksp/ksp/examples/tutorials/ex30.c

Please see attached code sample. The code compiles but does not solve the
system correctly. I would like to know what changes I would need to
​implement to get it working right. Thanks!

P.S.  Feel free to include the (corrected) code sample in the test/tutorial
folders of the development version.

On Sun, Apr 12, 2015 at 7:47 PM, Hong <hzhang at mcs.anl.gov> wrote:

> You can either use elemental directly, or use petsc-elemental interface.
> An example can be found at
> ~petsc/src/mat/examples/tests/ex145.c
>
> You may use petsc KSP interface instead. I just modified
> ~petsc/src/ksp/ksp/examples/tutorials/ex2.c
> so this example can be run with elemental with runtime options
> mpiexec -n 3 ./ex2 -pc_type lu -pc_factor_mat_solver_package elemental
> -mat_type elemental
> Norm of error 2.81086e-15 iterations 1
>
> Please using petsc-dev (master branch) for petsc-elemental interface.
>
> Hong
>
> On Sun, Apr 12, 2015 at 6:57 PM, Preyas Shah <shah.preyas at gmail.com>
> wrote:
>
>> Hi,
>>
>> I have been recently investigating the use of Petsc for solving a PDE
>> related to my research and web search suggests that I should use petsc with
>> elemental.
>>
>> So far, I was required to solve a matrix equation Ax=b where A was dense
>> (with number of non zeros =0) but the size of the matrix was order
>> 5000x5000. I employed the standard serial LU solver from Gnu Scientific
>> Library and obtained a decent runtime that served my needs.
>>
>> Now I am investigating the same problem in a particularly singular limit
>> of one parameters in my PDE. As a result, to obtain grid convergence on the
>> physical domain, I am forced to go to sizes of A beyond 30000x30000. I am
>> trying to find a good library that can solve such dense systems in
>> **parallel**. Petsc says its capable of doing dense linear algebra but my
>> web search hasn't shown me any examples where dense equations are solved in
>> **parallel**. A webpage showing a minimum working example would be enough.
>> Or any other advice :)
>>
>> Thanks for your time!
>> ​~Preyas
>>
>>
>


-- 
~
Preyas

Doctoral Researcher, MechE, Stanford Univ.

*"Can a man still be brave if he's afraid?".**"That is the only time he can
be brave."-- George R R Martin*
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