[petsc-users] question about PCMG

[Matthew Knepley]

On Fri, Sep 24, 2010 at 4:12 PM, Randall Mackie <rlmackie862 at gmail.com>wrote:

> I am interested in exploring whether or not the PCMG would be beneficial
> for my problem which I currently
> solve using a KSP of bcgs and an ILU PC on a DA.
>
> So, as a first step, I just wanted to see what happens if I switched my PC
> from ILU to PCMG using the
> Galerkin option.
>

PCMG is not really a preconditioner. It is the Platonic Ideal for a family
of preconditioners. Without knowledge
of the grid hierarchy, we cannot automatically determine interpolation and
restriction operators (and really we
need to know about the discretization here as well). That is why DMMG is in
PETSc. If we know you are on
a DA, we can do a reasonable job of computing these for you.

  Thanks,

     Matt


> So my command line options are:
>
> mpiexec -np 1 /home/rmackie/d3fwd/V3_2_PETSc_DA_PCMG/d3fwd \
>          -ksp_monitor_true_residual \
>          -ksp_type bcgs \
>          -pc_type mg \
>          -pc_mg_levels 1 \
>          -pc_mg_cycles v \
>          -pc_mg_galerkin \
>          -help \
> << EOF
>
>
> However, I keep getting this error message:
>
> Preconditioner (PC) Options
> -------------------------------------------------
>   -pc_type <ilu>: Preconditioner (one of) none jacobi pbjacobi bjacobi sor
> lu shell mg
>       eisenstat ilu icc cholesky asm ksp composite redundant nn mat
> fieldsplit galerkin exotic openmp asa cp bfbt lsc redistribute (PCSetType)
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation,
> probably memory access out of range
> [0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
> [0]PETSC ERROR: or see
> http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#Signal[0]PETSCERROR: or try
> http://valgrind.org on GNU/linux and Apple Mac OS X to find memory
> corruption errors
> [0]PETSC ERROR: likely location of problem given in stack below
> [0]PETSC ERROR: ---------------------  Stack Frames
> ------------------------------------
>   Multigrid options
> [0]PETSC ERROR: Note: The EXACT line numbers in the stack are not
> available,
> [0]PETSC ERROR:       INSTEAD the line number of the start of the function
> [0]PETSC ERROR:       is given.
> [0]PETSC ERROR: [0] PCSetFromOptions_MG line 318 src/ksp/pc/impls/mg/mg.c
> [0]PETSC ERROR: [0] PCSetFromOptions line 166 src/ksp/pc/interface/pcset.c
> [0]PETSC ERROR: [0] KSPSetFromOptions line 320 src/ksp/ksp/interface/itcl.c
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Signal received!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Petsc Release Version 3.1.0, Patch 4, Fri Jul 30 14:42:02
> CDT 2010
> [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: /home/rmackie/d3fwd/V3_2_PETSc_DA_PCMG/d3fwd on a linux-int
> named he999.prod.houston.nam.slb.com by rmackie Fri Sep 24 13:06:12 2010
> [0]PETSC ERROR: Libraries linked from
> /home/rmackie/SPARSE/PETsc/petsc-3.1-p4/linux-intel-debug/lib
> [0]PETSC ERROR: Configure run at Fri Sep 24 13:02:26 2010
> [0]PETSC ERROR: Configure options --with-fortran --with-fortran-kernels=1
> --with-blas-lapack-dir=/opt/intel/cmkl/10.2.2.025/lib/em64t-with-scalar-type=complex --with-debugging=1 --with-cc=mpiicc
> --with-cxx=mpiicpc --with-fc=mpiifort
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: User provided function() line 0 in unknown directory
> unknown file
> application called MPI_Abort(MPI_COMM_WORLD, 59) - process 0
>
>
> I am running the latest version of Petsc. Any help on getting past this
> error message would be appreciated.
>
> Randy M.
>
>


-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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