[petsc-users] FETI-DP implementation and call sequence

[Barry Smith]

   This is likely due to the horrible horrible fact that some of the bddc files only get compiled if ./configure is run with the option --with-pcbddc you will need to rerun ./configure and then make with that option.

   I pray that someone removes that horrible confusing configure option.

   Barry

On Sep 4, 2014, at 8:52 AM, Alp Kalpalp <alpkalpalp at gmail.com> wrote:

> Dear Stefano,
> 
> I have checked out "master" branch and merged with your stefano_zampini/pcbddc-primalfixe branch. configured, compiled and all tests are completed successfully. 
> Then, I tried to compile ex59 with make ex59, it results in unresolved external error. I believe your bddc_feti files are not included in compilation. 
> Since I am not experienced on how to solve issues in Petsc, I need to ask several questions;
> 
> 1-) Are there any global settings to add additonal directories to compilation  (src\ksp\pc\impls\bddc)
> 2-) or should I include these files on top of ex59 (AFAIK, including .c files is not a good thing)
> 3-) and finally what is the better way of helping you (creating another branch from yours or what)
> 
> Thanks in advance
> 
> 
> 
> 
> 
> 
> On Wed, Sep 3, 2014 at 6:18 PM, Stefano Zampini <stefano.zampini at gmail.com> wrote:
> FETIDP is in PETSc as a byproduct of the BDDC preconditioner (one is the dual of the other) and it does not have its own classes so far.
> 
> That said, you can experiment with FETI-DP only after having setup a BDDC preconditioner with the options and customization you prefer.
> Use http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/KSP/index.html for manual pages.
>  
> For an 'how to' with FETIDP, please see src/ksp/ksp/examples/tutorials/ex.59.c as Jed told you, specifically look at ComputeKSPFETIDP for obtaining the FETIDP matrix F (implemented Matrix-free) and the optimal FETIDP dirichlet preconditioner. Once you have F, you can use PCBDDCMatFETIDPGetRHS and PCBDDCMatFetiDPGetSolution to obtain a right-hand side for the FETIDP system and a physical solution from the solution of the FETIDP system.
> 
> I would recommend you to use the development version of the library and either use the ‘next’ branch or the ‘master' branch after having merged in the branch stefano_zampini/pcbddc-primalfixes. Note that ‘next’ also contains the new deluxe scaling operator for BDDC which is not available to use with FETI-DP.
> 
> If you have any other questions which can be useful for other PETSc users, please use the mailing list; otherwise you can contact me personally.
> 
> Stefano
> 
> 
> On Sep 3, 2014, at 5:19 PM, Jed Brown <jed at jedbrown.org> wrote:
> 
>> Matthew Knepley <knepley at gmail.com> writes:
>>>> 1- Is it possible to complete a FETI-DP solution with the provided
>>>> functions in current PetSc release?
>>>> 
>>> 
>>> There is no FETI-DP in PETSc. 
>> 
>> Wrong.  There is PCBDDC, which has the same eigenvalues as FETI-DP.  You
>> can enable it by configuring --with-pcbddc.  This will be turned on by
>> default soon.  It is fairly new, so you should use the branch 'master'
>> instead of the release.  It has an option to do FETI-DP instead of BDDC.
>> See src/ksp/ksp/examples/tutorials/ex59.c.
>> 
>> For either of these methods, you have to assemble a MATIS.  If you use
>> MatSetValuesLocal, most of your assembly code can stay the same.
>> 
>> Hopefully we can get better examples before the next release.  Stefano
>> (the author of PCBDDC, Cc'd) tests mostly with external packages, but we
>> really need more complete tests within PETSc.
> 
>