[petsc-users] create PC, KSP, ST separately and use in EPS

[Denis Davydov]

Thanks Jose for the prompt  (as always) reply. 
I will post further questions if I encounter any issues with the outlined approach.

Kind regards,
Denis 

> On 29 Oct 2015, at 18:39, Jose E. Roman <jroman at dsic.upv.es> wrote:
> 
>> 
>> El 29/10/2015, a las 13:32, Denis Davydov <davydden at gmail.com <mailto:davydden at gmail.com>> escribió:
>> 
>> Dear all, 
>> 
>> I am currently looking at ways to extend deal.II PETSc/SLEPc wrappers classes to allow 
>> specification of linear solvers and preconditioners to be used in SLEPc eigensolvers 
>> using deal.II objects and NOT the command line arguments.
> 
> Yes, current deal.II wrappers for SLEPc are quite limited.
> 
>> 
>> All examples and unit tests I came across in SLEPc work with EPSCreate() followed by 
>> EPSGetST(), STGetKSP() and KSPGetPC(). This however does not fit well into object-oriented C++ code.
>> Thus I plan to create each objects separately and pass them around.
>> 
>> I would like to ask if the way I see it (in terms of PETSc/SLEPc functions called) is conceptually correct:
>> 
>> — PETSc: Preconditioner class:
>> PCCreate()
>> PCSetType()
>> PCSetFromOptions();
>> —
>> 
>> — PETSc: Solver class (uses Preconditioner class):
>> KSPCreate()
>> KSPSetType()
>> KSPSetPC() // set PC created above
>> KSPSetConvergenceTest()
>> KSPSetFromOptions()
>> —
>> 
>> — SLEPc: SpectralTransformation class (uses Solver class)
>> STCreate()
>> STSetType()
>> STSetShift() // some specific settings to transformation
>> STSetKSP() // set KSP created above
>> —
>> 
>> — SLEPc: Eigensolver class (uses SpectralTransformation class)
>> EPSCreate()
>> EPSSetTolerances()
>> EPSSetConvergenceTest()
>> EPSSetWhichEigenpairs()
>> EPSSetProblemType()
>> EPSSetType()
>> EPSArnoldiSetDelayed() // any specific options to eigensolver
>> EPSSetST() // set spectral transformation created above
>> // solve
>> EPSSetDimensions()
>> EPSSetFromOptions()
>> EPSSolve()
>> —
>> 
>> Do this usage model sounds correct from SLEPc perspective?
> 
> I see no problem with this approach.
> 
>> What bothers me is that i do not call PCSetOperators()/PCSetUp() and KSPSetOperators()/KSPSetUp(), 
>> which one would call while setting up PETSc objects to solve SLAE.
>> Nonetheless I assume those functions are executed somewhere inside SLEPc depending on
>> SHEP/GHEP and ST to be used.
> 
> Correct, EPS/ST handle the KSP coefficient matrix so KSPSetUp() must be done at EPSSetUp() and not before.
> 
> Jose
> 
>> 
>> Kind regards,
>> Denis.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20151029/1ec5b7cd/attachment.html>