Hi Michele,

I suggest you try a different decomposition of your grid. With k levels, you should have at least 2^{k-1} grid nodes per coordinate direction in order to be able to correctly build a coarser mesh. In your case, you should have at least 8 nodes (leading to coarser levels of size 4, 2, and 1) in z direction.

Best regards,
Karli


On 08/13/2013 02:28 PM, Michele Rosso wrote:
Hi Barry,

I was finally able to try multigrid with a singular system and a finer grid.
GAMG works perfectly and has no problem in handling the singular system.
On the other hand, MG is giving me problem:

[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Argument out of range!
[0]PETSC ERROR: Partition in x direction is too fine! 32 64!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 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: ./hit on a arch-cray-xt5-pkgs-opt named nid01332 by
Unknown Tue Aug 13 15:06:21 2013
[0]PETSC ERROR: Libraries linked from
/nics/c/home/mrosso/LIBS/petsc-3.4.2/arch-cray-xt5-pkgs-opt/lib
[0]PETSC ERROR: Configure run at Wed Jul 31 22:48:06 2013

The input I used is:
-ksp_monitor -ksp_converged_reason -pc_type mg  -pc_mg_galerkin
-pc_mg_levels 4 -options_left

I am simulating a 256^3 grid with 256 processors. Since I am using a 2D
domain decomposition, each sub-domain contains 256x64x4 grid points.
To be consistent with my code indexing, I had to initialize DMDA with
reverse ordering, that is z,y,x, so when the error message says "x is
too fine" it actually means "z is too fine".
I was wondering what is the minimum number of nodes per direction that
would avoid this problem and how the number of levels is related to
minimum grid size required.
Thank you!

Michele


On 08/02/2013 03:11 PM, Barry Smith wrote:
On Aug 2, 2013, at 4:52 PM, Michele Rosso<mro...@uci.edu>  wrote:

Barry,

thank you very much for your help. I was trying to debug the error with no 
success!
Now it works like a charm for me too!
I have still two questions for you:

1) How did you choose the number of levels to use: trial and error?
    I just used 2 because it is more than one level :-).  When you use a finer 
mesh you can use more levels.

2) For a singular system (periodic), besides the nullspace removal, should I 
change any parameter?
    I don't know of anything.

    But there is a possible problem with -pc_mg_galerkin, PETSc does not 
transfer the null space information from the fine mesh to the other meshes and 
technically we really want the multigrid to remove the null space on all the 
levels but usually it will work without worrying about that.

    Barry

Again, thank you very much!

Michele

On 08/02/2013 02:38 PM, Barry Smith wrote:
    Finally got it. My failing memory. I had to add the line

    call KSPSetDMActive(ksp,PETSC_FALSE,ierr)

    immediately after KSPSetDM()   and

    change

     call DMCreateMatrix(da,MATMPIAIJ,A,ierr)

    to

     call DMCreateMatrix(da,MATAIJ,A,ierr)

     so it will work in both parallel and sequential then

ksp_monitor -ksp_converged_reason -pc_type mg -ksp_view  -pc_mg_galerkin 
-pc_mg_levels 2

works great with 2 levels.

    Barry




On Aug 1, 2013, at 6:29 PM, Michele Rosso
<mro...@uci.edu>
  wrote:


Barry,

no problem. I attached the full code in test_poisson_solver.tar.gz.
My test code is a very reduced version of my productive code (incompressible DNS 
code) thus fftw3 and the library 2decomp&fft are needed to run it.
I attached the 2decomp&fft version I used: it is a matter of minutes to install 
it, so you should not have any problem.
Please, contact me for any question/suggestion.
I the mean time I will try to debug it.

Michele




On 08/01/2013 04:19 PM, Barry Smith wrote:

    Run on one process until this is debugged. You can try the option

-start_in_debugger noxterm

and then call VecView(vec,0) in the debugger when it gives the error below. It 
seems like some objects are not getting their initial values set properly. Are 
you able to email the code so we can run it and figure out what is going on?

    Barry

On Aug 1, 2013, at 5:52 PM, Michele Rosso

<mro...@uci.edu>

  wrote:



Barry,

I checked the matrix: the element (0,0) is not zero, nor any other diagonal 
element is.
The matrix is symmetric positive define (i.e. the standard Poisson matrix).
Also, -da_refine is never used (see previous output).
I tried to run with -pc_type mg -pc_mg_galerkin -mg_levels_pc_type jacobi 
-mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues  
-ksp_view -options_left

and now the error is different:
0]PETSC ERROR: [1]PETSC ERROR: --------------------- Error Message 
------------------------------------
[1]PETSC ERROR: Floating point exception!
[1]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at 
beginning of function: Parameter number 2!
[1]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[1]PETSC ERROR: See docs/changes/index.html for recent updates.
[1]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[2]PETSC ERROR: --------------------- Error Message 
------------------------------------
[2]PETSC ERROR: Floating point exception!
[2]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at 
beginning of function: Parameter number 2!
[2]PETSC ERROR: 
------------------------------------------------------------------------
[2]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[2]PETSC ERROR: See docs/changes/index.html for recent updates.
[2]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[2]PETSC ERROR: [3]PETSC ERROR: --------------------- Error Message 
------------------------------------
[3]PETSC ERROR: Floating point exception!
[3]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at 
beginning of function: Parameter number 2!
[3]PETSC ERROR: 
------------------------------------------------------------------------
[3]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[3]PETSC ERROR: See docs/changes/index.html for recent updates.
[3]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[3]PETSC ERROR: See docs/index.html for manual pages.
[3]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: See docs/index.html for manual pages.
[1]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Aug  1 
15:43:16 2013
[1]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[1]PETSC ERROR: See docs/index.html for manual pages.
[2]PETSC ERROR: 
------------------------------------------------------------------------
[2]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Aug  1 
15:43:16 2013
[2]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[2]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[2]PETSC ERROR: [3]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by 
mic Thu Aug  1 15:43:16 2013
[3]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[3]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[3]PETSC ERROR: Configure options
Configure run at Thu Aug  1 12:01:44 2013
[1]PETSC ERROR: Configure options
[1]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: VecValidValues() line 28 in src/vec/vec/interface/rvector.c
Configure options
[2]PETSC ERROR: 
------------------------------------------------------------------------
[2]PETSC ERROR: VecValidValues() line 28 in src/vec/vec/interface/rvector.c
[3]PETSC ERROR: 
------------------------------------------------------------------------
[3]PETSC ERROR: VecValidValues() line 28 in src/vec/vec/interface/rvector.c
[3]PETSC ERROR: [1]PETSC ERROR: MatMult() line 2174 in 
src/mat/interface/matrix.c
[1]PETSC ERROR: [2]PETSC ERROR: MatMult() line 2174 in 
src/mat/interface/matrix.c
[2]PETSC ERROR: KSP_MatMult() line 204 in 
src/ksp/ksp/impls/cheby//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
MatMult() line 2174 in src/mat/interface/matrix.c
[3]PETSC ERROR: KSP_MatMult() line 204 in 
src/ksp/ksp/impls/cheby//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[3]PETSC ERROR: KSP_MatMult() line 204 in 
src/ksp/ksp/impls/cheby//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[1]PETSC ERROR: KSPSolve_Chebyshev() line 504 in src/ksp/ksp/impls/cheby/cheby.c
[2]PETSC ERROR: KSPSolve_Chebyshev() line 504 in src/ksp/ksp/impls/cheby/cheby.c
[2]PETSC ERROR: KSPSolve_Chebyshev() line 504 in src/ksp/ksp/impls/cheby/cheby.c
[3]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[1]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[1]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
[3]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
[1]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[2]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[2]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[3]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[3]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[1]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[1]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[2]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[2]PETSC ERROR: [3]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[3]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[1]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[1]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[2]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[3]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
--------------------- Error Message ------------------------------------
[0]PETSC ERROR: Floating point exception!
[0]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at 
beginning of function: Parameter number 2!
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 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 Aug  1 
15:43:16 2013
[0]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[0]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[0]PETSC ERROR: Configure options
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: VecValidValues() line 28 in src/vec/vec/interface/rvector.c
[0]PETSC ERROR: MatMult() line 2174 in src/mat/interface/matrix.c
[0]PETSC ERROR: KSP_MatMult() line 204 in 
src/ksp/ksp/impls/cheby//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[0]PETSC ERROR: KSPSolve_Chebyshev() line 504 in src/ksp/ksp/impls/cheby/cheby.c
[0]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[0]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[0]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c

#PETSc Option Table entries:
-ksp_view
-mg_levels_ksp_chebyshev_estimate_eigenvalues
-mg_levels_ksp_type chebyshev
-mg_levels_pc_type jacobi
-options_left
-pc_mg_galerkin
-pc_type mg
#End of PETSc Option Table entries
There are no unused options.

Michele


On 08/01/2013 03:27 PM, Barry Smith wrote:


   Do a MatView() on A before the solve (remove the -da_refine 4) so it is 
small. Is the 0,0 entry 0? If the matrix has zero on the diagonals you cannot 
us Gauss-Seidel as the smoother.  You can start with -mg_levels_pc_type jacobi 
-mg_levels_ksp_type chebychev -mg_levels_ksp_chebyshev_estimate_eigenvalues

    Is the matrix a Stokes-like matrix? If so then different preconditioners 
are in order.

    Barry

On Aug 1, 2013, at 5:21 PM, Michele Rosso


<mro...@uci.edu>


  wrote:




Barry,

here it is the fraction of code where I set the rhs term and the matrix.

        ! Create matrix
        call form_matrix( A , qrho, lsf, head )
        call MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY,ierr)
        call MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY,ierr)

        ! Create rhs term
        call form_rhs(work, qrho, lsf, b , head)

        ! Solve system
        call KSPSetFromOptions(ksp,ierr)
        call KSPSetUp(ksp,ierr)
        call KSPSolve(ksp,b,x,ierr)
        call KSPGetIterationNumber(ksp, iiter ,ierr)

The subroutine form_matrix returns the Mat object A that is filled by using  
MatSetValuesStencil.
qrho, lsf and head are additional arguments that are needed to compute the 
matrix value.


Michele



On 08/01/2013 03:11 PM, Barry Smith wrote:



   Where are you putting the values into the matrix? It seems the matrix has no 
values in it? The code is stopping because in the Gauss-Seidel smoothing it has 
detected zero diagonals.

    Barry


On Aug 1, 2013, at 4:47 PM, Michele Rosso


<mro...@uci.edu>


  wrote:




Barry,

I run with :   -pc_type mg -pc_mg_galerkin -da_refine 4  -ksp_view -options_left

For the test I use a 64^3 grid and 4 processors.

The output is:

[2]PETSC ERROR: --------------------- Error Message 
------------------------------------
[2]PETSC ERROR: Arguments are incompatible!
[2]PETSC ERROR: Zero diagonal on row 0!
[2]PETSC ERROR: 
------------------------------------------------------------------------
[2]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[2]PETSC ERROR: See docs/changes/index.html for recent updates.
[2]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[2]PETSC ERROR: See docs/index.html for manual pages.
[2]PETSC ERROR: 
------------------------------------------------------------------------
[2]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Aug  1 
14:44:04 2013
[0]PETSC ERROR: [2]PETSC ERROR: Libraries linked from 
/opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[2]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[2]PETSC ERROR: Configure options
[2]PETSC ERROR: 
------------------------------------------------------------------------
[2]PETSC ERROR: MatInvertDiagonal_SeqAIJ() line 1457 in 
src/mat/impls/aij/seq/aij.c
[2]PETSC ERROR: MatSOR_SeqAIJ() line 1489 in src/mat/impls/aij/seq/aij.c
--------------------- Error Message ------------------------------------
[2]PETSC ERROR: MatSOR_MPIAIJ() line 1623 in src/mat/impls/aij/mpi/mpiaij.c
[2]PETSC ERROR: MatSOR() line 3649 in src/mat/interface/matrix.c
[2]PETSC ERROR: [0]PETSC ERROR: PCApply_SOR() line 35 in 
src/ksp/pc/impls/sor/sor.c
[2]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[2]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/interface//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
Arguments are incompatible!
[2]PETSC ERROR: KSPInitialResidual() line 64 in src/ksp/ksp/interface/itres.c
[2]PETSC ERROR: KSPSolve_GMRES() line 239 in src/ksp/ksp/impls/gmres/gmres.c
[2]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: [0]PETSC ERROR: KSPSolve_Chebyshev() line 409 in 
src/ksp/ksp/impls/cheby/cheby.c
[2]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
Zero diagonal on row 0!
[2]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[2]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: [2]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[2]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
------------------------------------------------------------------------
[2]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[3]PETSC ERROR: [0]PETSC ERROR: See docs/faq.html for hints about trouble 
shooting.
[0]PETSC ERROR: --------------------- Error Message 
------------------------------------
[3]PETSC ERROR: Arguments are incompatible!
[3]PETSC ERROR: Zero diagonal on row 0!
[3]PETSC ERROR: 
------------------------------------------------------------------------
[3]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[3]PETSC ERROR: See docs/changes/index.html for recent updates.
[3]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[3]PETSC ERROR: See docs/index.html for manual pages.
[3]PETSC ERROR: 
------------------------------------------------------------------------
See docs/index.html for manual pages.
[3]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Aug  1 
14:44:04 2013
[3]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[1]PETSC ERROR: [3]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[3]PETSC ERROR: Configure options
[3]PETSC ERROR: 
------------------------------------------------------------------------
[3]PETSC ERROR: --------------------- Error Message 
------------------------------------
MatInvertDiagonal_SeqAIJ() line 1457 in src/mat/impls/aij/seq/aij.c
[3]PETSC ERROR: MatSOR_SeqAIJ() line 1489 in src/mat/impls/aij/seq/aij.c
[3]PETSC ERROR: [0]PETSC ERROR: MatSOR_MPIAIJ() line 1623 in 
src/mat/impls/aij/mpi/mpiaij.c
[1]PETSC ERROR: Arguments are incompatible!
[1]PETSC ERROR: Zero diagonal on row 0!
[1]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013
[1]PETSC ERROR: See docs/changes/index.html for recent updates.
[1]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[1]PETSC ERROR: See docs/index.html for manual pages.
[1]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Aug  1 
14:44:04 2013
[1]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[1]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[1]PETSC ERROR: Configure options
[1]PETSC ERROR: 
------------------------------------------------------------------------
[1]PETSC ERROR: MatInvertDiagonal_SeqAIJ() line 1457 in 
src/mat/impls/aij/seq/aij.c
[1]PETSC ERROR: [3]PETSC ERROR: MatSOR() line 3649 in src/mat/interface/matrix.c
[3]PETSC ERROR: PCApply_SOR() line 35 in src/ksp/pc/impls/sor/sor.c
[3]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[3]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/interface//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[3]PETSC ERROR: KSPInitialResidual() line 64 in src/ksp/ksp/interface/itres.c
[3]PETSC ERROR: KSPSolve_GMRES() line 239 in src/ksp/ksp/impls/gmres/gmres.c
[3]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[3]PETSC ERROR: KSPSolve_Chebyshev() line 409 in src/ksp/ksp/impls/cheby/cheby.c
[3]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[3]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
[3]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[3]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[3]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[3]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[3]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
MatSOR_SeqAIJ() line 1489 in src/mat/impls/aij/seq/aij.c
[1]PETSC ERROR: MatSOR_MPIAIJ() line 1623 in src/mat/impls/aij/mpi/mpiaij.c
[1]PETSC ERROR: MatSOR() line 3649 in src/mat/interface/matrix.c
[1]PETSC ERROR: PCApply_SOR() line 35 in src/ksp/pc/impls/sor/sor.c
[1]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[1]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/interface//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[1]PETSC ERROR: KSPInitialResidual() line 64 in src/ksp/ksp/interface/itres.c
[1]PETSC ERROR: KSPSolve_GMRES() line 239 in src/ksp/ksp/impls/gmres/gmres.c
[1]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[1]PETSC ERROR: KSPSolve_Chebyshev() line 409 in src/ksp/ksp/impls/cheby/cheby.c
[1]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[1]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
[1]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[1]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[1]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[1]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[1]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
------------------------------------------------------------------------
[0]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Aug  1 
14:44:04 2013
[0]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.2/linux-gnu-dbg/lib
[0]PETSC ERROR: Configure run at Thu Aug  1 12:01:44 2013
[0]PETSC ERROR: Configure options
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: MatInvertDiagonal_SeqAIJ() line 1457 in 
src/mat/impls/aij/seq/aij.c
[0]PETSC ERROR: MatSOR_SeqAIJ() line 1489 in src/mat/impls/aij/seq/aij.c
[0]PETSC ERROR: MatSOR_MPIAIJ() line 1623 in src/mat/impls/aij/mpi/mpiaij.c
[0]PETSC ERROR: MatSOR() line 3649 in src/mat/interface/matrix.c
[0]PETSC ERROR: PCApply_SOR() line 35 in src/ksp/pc/impls/sor/sor.c
[0]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/interface//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[0]PETSC ERROR: KSPInitialResidual() line 64 in src/ksp/ksp/interface/itres.c
[0]PETSC ERROR: KSPSolve_GMRES() line 239 in src/ksp/ksp/impls/gmres/gmres.c
[0]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: KSPSolve_Chebyshev() line 409 in src/ksp/ksp/impls/cheby/cheby.c
[0]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCMGMCycle_Private() line 19 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCApply_MG() line 330 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCApply() line 442 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSP_PCApply() line 227 in 
src/ksp/ksp/impls/cg//opt/petsc/petsc-3.4.2/include/petsc-private/kspimpl.h
[0]PETSC ERROR: KSPSolve_CG() line 175 in src/ksp/ksp/impls/cg/cg.c
[0]PETSC ERROR: KSPSolve() line 441 in src/ksp/ksp/interface/itfunc.c
#PETSc Option Table entries:
-da_refine 4
-ksp_view
-options_left
-pc_mg_galerkin
-pc_type mg
#End of PETSc Option Table entries
There is one unused database option. It is:
Option left: name:-da_refine value: 4


Here is the code I use to setup DMDA and KSP:

     call DMDACreate3d( PETSC_COMM_WORLD ,                                  &
                     & DMDA_BOUNDARY_PERIODIC , DMDA_BOUNDARY_PERIODIC,     &
                     & DMDA_BOUNDARY_PERIODIC , DMDA_STENCIL_STAR,          &
                     & N_Z , N_Y , N_X , N_B3 , N_B2 , 1_ip,  1_ip , 1_ip , &
                     & int(NNZ,ip) ,int(NNY,ip) , NNX, da , ierr)
          ! Create Global Vectors
     call DMCreateGlobalVector(da,b,ierr)
     call VecDuplicate(b,x,ierr)
          ! Set initial guess for first use of the module to 0
     call VecSet(x,0.0_rp,ierr)
          ! Create matrix
     call DMCreateMatrix(da,MATMPIAIJ,A,ierr)
           ! Create solver
     call KSPCreate(PETSC_COMM_WORLD,ksp,ierr)
     call KSPSetDM(ksp,da,ierr)
     call KSPSetOperators(ksp,A,A,DIFFERENT_NONZERO_PATTERN,ierr)
!    call KSPSetOperators(ksp,A,A,SAME_NONZERO_PATTERN,ierr)
     call KSPSetType(ksp,KSPCG,ierr)
     call KSPSetNormType(ksp,KSP_NORM_UNPRECONDITIONED,ierr) ! Real residual
     call KSPSetInitialGuessNonzero(ksp,PETSC_TRUE,ierr)
     call KSPSetTolerances(ksp, tol ,PETSC_DEFAULT_DOUBLE_PRECISION,&
         & PETSC_DEFAULT_DOUBLE_PRECISION,PETSC_DEFAULT_INTEGER,ierr)

     ! To allow using option from command line
     call KSPSetFromOptions(ksp,ierr)


Michele




On 08/01/2013 01:04 PM, Barry Smith wrote:



    You can use the option -pc_mg_galerkin  and then MG will compute the 
coarser matrices with a sparse matrix matrix matrix product so you should not 
need to change your code to try it out.  You still need to use the KSPSetDM() 
and -da_refine n to get it working

    If it doesn't work, send us all the output.

    Barry


On Aug 1, 2013, at 2:47 PM, Michele Rosso



<mro...@uci.edu>



  wrote:





Barry,
you are correct, I did not use it. I think I get now where is the problem. 
Correct me if I am wrong, but for the
geometric multigrid to work, ksp must be provided with subroutines to compute 
the matrix and the rhs at any level through
KSPSetComputeOperators and KSPSetComputeRHS.
I do not do that, I simply build a rhs vector and a matrix and then I solve the 
system.
If you confirm what I just wrote, I will try to modify my code accordingly and 
get back to you.
Thank you,
Michele
  On 08/01/2013 11:48 AM, Barry Smith wrote:




   Do you use KSPSetDM(ksp,da);  ?  See src/ksp/ksp/examples/tutorials/ex19.c

    Barry

On Aug 1, 2013, at 1:35 PM, Michele Rosso




<mro...@uci.edu>




  wrote:






Barry,

I am using a finite difference Cartesian uniform grid and DMDA and so far it 
has not given me any problem.
I am using a ksp solver (not snes). In a previous thread, I was told an odd 
number of grid points was needed for the geometric multigrid, is that correct?
I tried to run my case with


-pc_type mg -da_refine 4



but it does not seem to use the -da_refine option:

mpiexec   -np 4 ./test  -pc_type mg -da_refine 4  -ksp_view -options_left


KSP Object: 4 MPI processes
  type: cg
  maximum iterations=10000
  tolerances:  relative=1e-08, absolute=1e-50, divergence=10000
  left preconditioning
  using nonzero initial guess
  using UNPRECONDITIONED norm type for convergence test
PC Object: 4 MPI processes
  type: mg
    MG: type is MULTIPLICATIVE, levels=1 cycles=v
      Cycles per PCApply=1
      Not using Galerkin computed coarse grid matrices
  Coarse grid solver -- level -------------------------------
    KSP Object:    (mg_levels_0_)     4 MPI processes
      type: chebyshev
        Chebyshev: eigenvalue estimates:  min = 0.134543, max = 1.47998
        Chebyshev: estimated using:  [0 0.1; 0 1.1]
        KSP Object:        (mg_levels_0_est_)         4 MPI processes
          type: gmres
            GMRES: restart=30, using Classical (unmodified) Gram-Schmidt 
Orthogonalization with no iterative refinement
            GMRES: happy breakdown tolerance 1e-30
          maximum iterations=10, initial guess is zero
          tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
          left preconditioning
          using NONE norm type for convergence test
        PC Object:        (mg_levels_0_)         4 MPI processes
          type: sor
            SOR: type = local_symmetric, iterations = 1, local iterations = 1, 
omega = 1
          linear system matrix = precond matrix:
          Matrix Object:           4 MPI processes
            type: mpiaij
            rows=262144, cols=262144
            total: nonzeros=1835008, allocated nonzeros=1835008
            total number of mallocs used during MatSetValues calls =0
      maximum iterations=1, initial guess is zero
      tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
      left preconditioning
      using NONE norm type for convergence test
    PC Object:    (mg_levels_0_)     4 MPI processes
      type: sor
        SOR: type = local_symmetric, iterations = 1, local iterations = 1, 
omega = 1
      linear system matrix = precond matrix:
      Matrix Object:       4 MPI processes
        type: mpiaij
        rows=262144, cols=262144
        total: nonzeros=1835008, allocated nonzeros=1835008
        total number of mallocs used during MatSetValues calls =0
  linear system matrix = precond matrix:
  Matrix Object:   4 MPI processes
    type: mpiaij
    rows=262144, cols=262144
    total: nonzeros=1835008, allocated nonzeros=1835008
    total number of mallocs used during MatSetValues calls =0
Solution       =    1.53600013     sec
#PETSc Option Table entries:
-da_refine 4
-ksp_view
-options_left
-pc_type mg
#End of PETSc Option Table entries
There is one unused database option. It is:
Option left: name:-da_refine value: 4

Michele

On 08/01/2013 11:21 AM, Barry Smith wrote:





    What kind of mesh are you using? Are you using DMDA? If you are using DMDA (and have 
written your code to use it "correctly") then it should be trivial to run with 
geometric multigrid and geometric multigrid should be a bit faster.

    For example on src/snes/examples/tutorials/ex19.c   I run with ./ex19 
-pc_type mg -da_refine 4 and it refines the original DMDA 4 times and uses 
geometric multigrid with 5 levels.


    Barry


On Aug 1, 2013, at 1:14 PM, Michele Rosso




<mro...@uci.edu>




  wrote:






Hi,

I am successfully using PETSc (v3.4.2)  to solve a 3D Poisson's equation with 
CG + GAMG as I was suggested to do in a previous thread.
So far I am using GAMG with the default settings, i.e.

-pc_type gamg -pc_gamg_agg_nsmooths 1

The speed of the solution is satisfactory, but I would like to know if you have 
any suggestions to further speed it up, particularly
if there is any parameters worth looking into to achieve an even faster 
solution, for example number of levels and so on.
So far I am using Dirichlet's BCs for my test case, but I will soon have 
periodic conditions: in this case, does GAMG require particular settings?
Finally, I did not try geometric multigrid: do you think it is worth a shot?

Here are my current settings:

I run with

-pc_type gamg -pc_gamg_agg_nsmooths 1 -ksp_view -options_left

and the output is:

KSP Object: 4 MPI processes
   type: cg
   maximum iterations=10000
   tolerances:  relative=1e-08, absolute=1e-50, divergence=10000
   left preconditioning
   using nonzero initial guess
   using UNPRECONDITIONED norm type for convergence test
PC Object: 4 MPI processes
   type: gamg
     MG: type is MULTIPLICATIVE, levels=3 cycles=v
       Cycles per PCApply=1
       Using Galerkin computed coarse grid matrices
   Coarse grid solver -- level -------------------------------
     KSP Object:    (mg_coarse_)     4 MPI processes
       type: preonly
       maximum iterations=1, initial guess is zero
       tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
       left preconditioning
       using NONE norm type for convergence test
     PC Object:    (mg_coarse_)     4 MPI processes
       type: bjacobi
         block Jacobi: number of blocks = 4
         Local solve info for each block is in the following KSP and PC objects:
       [0] number of local blocks = 1, first local block number = 0
                 [0] local block number 0
KSP Object:          (mg_coarse_sub_)         1 MPI processes
           type: preonly
           maximum iterations=1, initial guess is zero
                 tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
KSP Object:        (mg_coarse_sub_)            left preconditioning
           using NONE norm type for convergence test
           PC Object:        (mg_coarse_sub_)       1 MPI processes
           type: preonly
          1 MPI processes
           type: lu
           maximum iterations=1, initial guess is zero
           tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
           LU: out-of-place factorization
             left preconditioning
           using NONE norm type for convergence test
           PC Object:        (mg_coarse_sub_)         1 MPI processes
           type: lu
           tolerance for zero pivot 2.22045e-14
             using diagonal shift on blocks to prevent zero pivot
             matrix ordering: nd
             LU: out-of-place factorization
             tolerance for zero pivot 2.22045e-14
             using diagonal shift on blocks to prevent zero pivot
             matrix ordering: nd
             factor fill ratio given 5, needed 0
               Factored matrix follows:
             factor fill ratio given 5, needed 4.13207
               Factored matrix follows:
                   Matrix Object:              Matrix Object:                 1 
MPI processes
                   type: seqaij
                     rows=395, cols=395
                     package used to perform factorization: petsc
                   total: nonzeros=132379, allocated nonzeros=132379
                   total number of mallocs used during MatSetValues calls =0
                         not using I-node routines
            1 MPI processes
                   type: seqaij
           linear system matrix = precond matrix:
                     rows=0, cols=0
                     package used to perform factorization: petsc
                   total: nonzeros=1, allocated nonzeros=1
                     total number of mallocs used during MatSetValues calls =0
                       not using I-node routines
               linear system matrix = precond matrix:
   Matrix Object:             1 MPI processes
             type: seqaij
           Matrix Object:KSP Object:           1 MPI processes
             type: seqaij
             rows=0, cols=0
             total: nonzeros=0, allocated nonzeros=0
             total number of mallocs used during MatSetValues calls =0
                 not using I-node routines
           rows=395, cols=395
             total: nonzeros=32037, allocated nonzeros=32037
             total number of mallocs used during MatSetValues calls =0
               not using I-node routines
           - - - - - - - - - - - - - - - - - -
           KSP Object:        (mg_coarse_sub_)         1 MPI processes
           type: preonly
           maximum iterations=1, initial guess is zero
           tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
           left preconditioning
           using NONE norm type for convergence test
         PC Object:        (mg_coarse_sub_)         1 MPI processes
           type: lu
             LU: out-of-place factorization
             tolerance for zero pivot 2.22045e-14
             using diagonal shift on blocks to prevent zero pivot
             matrix ordering: nd
             factor fill ratio given 5, needed 0
               Factored matrix follows:
                 Matrix Object:                 1 MPI processes
                   type: seqaij
                   rows=0, cols=0
                   package used to perform factorization: petsc
                   total: nonzeros=1, allocated nonzeros=1
                   total number of mallocs used during MatSetValues calls =0
                     not using I-node routines
           linear system matrix = precond matrix:
           Matrix Object:           1 MPI processes
             type: seqaij
             rows=0, cols=0
             total: nonzeros=0, allocated nonzeros=0
             total number of mallocs used during MatSetValues calls =0
               not using I-node routines
   (mg_coarse_sub_)         1 MPI processes
           type: preonly
           maximum iterations=1, initial guess is zero
           tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
           left preconditioning
           using NONE norm type for convergence test
         PC Object:        (mg_coarse_sub_)         1 MPI processes
           type: lu
             LU: out-of-place factorization
             tolerance for zero pivot 2.22045e-14
             using diagonal shift on blocks to prevent zero pivot
             matrix ordering: nd
             factor fill ratio given 5, needed 0
               Factored matrix follows:
                 Matrix Object:                 1 MPI processes
                   type: seqaij
                   rows=0, cols=0
                   package used to perform factorization: petsc
                   total: nonzeros=1, allocated nonzeros=1
                   total number of mallocs used during MatSetValues calls =0
                     not using I-node routines
           linear system matrix = precond matrix:
           Matrix Object:           1 MPI processes
             type: seqaij
             rows=0, cols=0
             total: nonzeros=0, allocated nonzeros=0
             total number of mallocs used during MatSetValues calls =0
               not using I-node routines
       [1] number of local blocks = 1, first local block number = 1
         [1] local block number 0
         - - - - - - - - - - - - - - - - - -
       [2] number of local blocks = 1, first local block number = 2
         [2] local block number 0
         - - - - - - - - - - - - - - - - - -
       [3] number of local blocks = 1, first local block number = 3
         [3] local block number 0
         - - - - - - - - - - - - - - - - - -
       linear system matrix = precond matrix:
       Matrix Object:       4 MPI processes
         type: mpiaij
         rows=395, cols=395
         total: nonzeros=32037, allocated nonzeros=32037
         total number of mallocs used during MatSetValues calls =0
           not using I-node (on process 0) routines
   Down solver (pre-smoother) on level 1 -------------------------------
     KSP Object:    (mg_levels_1_)     4 MPI processes
       type: chebyshev
         Chebyshev: eigenvalue estimates:  min = 0.0636225, max = 1.33607
       maximum iterations=2
       tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
       left preconditioning
       using nonzero initial guess
       using NONE norm type for convergence test
     PC Object:    (mg_levels_1_)     4 MPI processes
       type: jacobi
       linear system matrix = precond matrix:
       Matrix Object:       4 MPI processes
         type: mpiaij
         rows=23918, cols=23918
         total: nonzeros=818732, allocated nonzeros=818732
         total number of mallocs used during MatSetValues calls =0
           not using I-node (on process 0) routines
   Up solver (post-smoother) same as down solver (pre-smoother)
   Down solver (pre-smoother) on level 2 -------------------------------
     KSP Object:    (mg_levels_2_)     4 MPI processes
       type: chebyshev
         Chebyshev: eigenvalue estimates:  min = 0.0971369, max = 2.03987
       maximum iterations=2
       tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
       left preconditioning
       using nonzero initial guess
       using NONE norm type for convergence test
     PC Object:    (mg_levels_2_)     4 MPI processes
       type: jacobi
       linear system matrix = precond matrix:
       Matrix Object:       4 MPI processes
         type: mpiaij
         rows=262144, cols=262144
         total: nonzeros=1835008, allocated nonzeros=1835008
         total number of mallocs used during MatSetValues calls =0
   Up solver (post-smoother) same as down solver (pre-smoother)
   linear system matrix = precond matrix:
   Matrix Object:   4 MPI processes
     type: mpiaij
     rows=262144, cols=262144
     total: nonzeros=1835008, allocated nonzeros=1835008
     total number of mallocs used during MatSetValues calls =0
#PETSc Option Table entries:
-ksp_view
-options_left
-pc_gamg_agg_nsmooths 1
-pc_type gamg
#End of PETSc Option Table entries
There are no unused options.


Thank you,
Michele





<test_poisson_solver.tar.gz><2decomp_fft-1.5.847-modified.tar.gz>




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