[petsc-users] KSPSetDM problem

[Michele Rosso]

Barry,

thank you.
I have another question: how does petsc compute the restriction 
(assuming  the user does not supply his own restriction)?
Does it use a simple transpose of the interpolation operator? Could you 
point me to the source code where this is done?

Thank you,
Michele

On 11/14/2013 06:51 PM, Barry Smith wrote:
> https://bitbucket.org/petsc/petsc/wiki/Home#markdown-header-contributing-a-small-patch
>
> On Nov 14, 2013, at 8:29 PM, Michele Rosso <mrosso at uci.edu> wrote:
>
>> Barry,
>>
>> thank you. I will have to go with option 1) since with 2) the number of iterations is almost the double (I tried with ex34).
>> I am testing the piecewise constant interpolation for periodic BCs we discussed about in a previous conversation: in case I am successful, how do I submit the fix?
>>
>> Michele
>>
>> On 11/14/2013 06:11 PM, Barry Smith wrote:
>>>     Since you set the DM inactive   the PCSetUp_MG() has no code to compute the coarser grid operators. You need to either
>>>
>>> 1) provide a DMKSPSetComputeOperators () function that will compute the operator for all levels or
>>>
>>> 2) run with -pc_mg_galerkin to have the coarse grid operators computed by multiplying the fine grid operator by the restriction/interpolation.
>>>
>>>     Barry
>>>
>>> On Nov 14, 2013, at 7:49 PM, Michele Rosso
>>> <mrosso at uci.edu>
>>>   wrote:
>>>
>>>
>>>> Hi,
>>>>
>>>> I am  solving a Poisson equation (cell-centered discretization) with multigrid.
>>>> I am using a 2D version of ksp/ksp/examples/tutorials/ex34.c as a reference.
>>>> The following code performs the same calculations as ex34:
>>>>
>>>>    call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
>>>>
>>>>      call DMDACreate2d(PETSC_COMM_WORLD, DMDA_BOUNDARY_NONE, DMDA_BOUNDARY_NONE,&
>>>>           & DMDA_STENCIL_STAR, 16, 16, PETSC_DECIDE, PETSC_DECIDE, &
>>>>           & 1, 1, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER,da,ierr)
>>>>      call DMDASetInterpolationType(da, DMDA_Q0, ierr);
>>>>      call DMCreateGlobalVector(da,b,ierr)
>>>>      call create_rhs(da,b)
>>>>      call DMCreateMatrix(da,'aij',A,ierr)
>>>>      call create_matrix(da,A)
>>>>      call VecDuplicate(b,x,ierr)
>>>>      
>>>>      ! Create solver
>>>>      call KSPCreate(PETSC_COMM_WORLD,solver,ierr)
>>>>      call KSPSetDM(solver,da,ierr)
>>>>      call KSPSetDMActive(solver,PETSC_FALSE,ierr)
>>>>      call KSPSetOperators(solver,A,A,SAME_NONZERO_PATTERN,ierr)
>>>>      call KSPSetType(solver,'cg',ierr)
>>>>      call KSPSetNormType(solver,KSP_NORM_UNPRECONDITIONED,ierr)
>>>>      call KSPSetFromOptions(solver,ierr)
>>>>      call KSPSolve(solver,b,x,ierr)
>>>>      
>>>>      rerr = error(da,x)
>>>>      
>>>>      call PetscFinalize(ierr)
>>>>
>>>>
>>>> Both ex34 and my code produce exactly the same results except when I run with
>>>>
>>>> -ksp_view -ksp_monitor_true_residual -ksp_converged_reason -ksp_type cg -pc_type mg -pc_mg_levels 4
>>>>
>>>> In this case my code results in the following error, despite KSPSetDMActive is used after KSPSetDM:
>>>>
>>>> [0]PETSC ERROR: --------------------- Error Message ------------------------------------
>>>> [0]PETSC ERROR: Object is in wrong state!
>>>> [0]PETSC ERROR: You called KSPSetDM() but did not use DMKSPSetComputeOperators() or KSPSetDMActive(dm,PETSC_FALSE);!
>>>> [0]PETSC ERROR: ------------------------------------------------------------------------
>>>> [0]PETSC ERROR: Petsc Release Version 3.4.3, Oct, 15, 2013
>>>> [0]PETSC ERROR: See docs/changes/index.html for recent updates.
>>>> [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
>>>> [0]PETSC ERROR: See docs/index.html for manual pages.
>>>> [0]PETSC ERROR: ------------------------------------------------------------------------
>>>> [0]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Nov 14 17:38:23 2013
>>>> [0]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.3/linux-gnu-dbg/lib
>>>> [0]PETSC ERROR: Configure run at Tue Oct 29 22:43:45 2013
>>>> [0]PETSC ERROR: Configure options --known-mpi-shared="0 " --known-memcmp-ok  --with-debugging="1 " --with-fortran-datatypes --with-shared-libraries=0 --with-dynamic-loading=0 --with-mpi-compilers="1 " --download-blacs="1 " --download-superlu_dist="1 " --download-metis="1 " --download-parmetis="1 " --download-ml=1 PETSC_ARCH=linux-gnu-dbg
>>>> [0]PETSC ERROR: ------------------------------------------------------------------------
>>>> [0]PETSC ERROR: KSPSetUp() line 230 in /opt/petsc/petsc-3.4.3/src/ksp/ksp/interface/itfunc.c
>>>> [0]PETSC ERROR: PCSetUp_MG() line 730 in /opt/petsc/petsc-3.4.3/src/ksp/pc/impls/mg/mg.c
>>>> [0]PETSC ERROR: PCSetUp() line 890 in /opt/petsc/petsc-3.4.3/src/ksp/pc/interface/precon.c
>>>> [0]PETSC ERROR: KSPSetUp() line 278 in /opt/petsc/petsc-3.4.3/src/ksp/ksp/interface/itfunc.c
>>>> [0]PETSC ERROR: KSPSolve() line 399 in /opt/petsc/petsc-3.4.3/src/ksp/ksp/interface/itfunc.c
>>>>
>>>>
>>>> Am I missing anything?
>>>> Thank you,
>>>>
>>>> Michele
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>