[petsc-users] fieldsplit recursive

[Anton Popov]

Dear petsc team,

I'm trying to use fieldsplit preconditioner for the velocity block in 
the Stokes system which is also preconditioned by
fieldsplit (kind of recursive).

Running example 42 from src/ksp/ksp/examples/tutorials with petsc-3.2, 
as follows:

mpiexec -np 4 ./ex42 \
-stokes_ksp_type gcr \
-stokes_ksp_rtol 1.0e-6 \
-stokes_pc_type fieldsplit \
-stokes_pc_fieldsplit_type SCHUR \
-stokes_pc_fieldsplit_schur_factorization_type UPPER \
-stokes_fieldsplit_u_ksp_type fgmres \
-stokes_fieldsplit_u_ksp_rtol 1e-3 \
-stokes_fieldsplit_u_pc_type fieldsplit \
-stokes_fieldsplit_u_fieldsplit_ksp_type preonly \
-stokes_fieldsplit_u_fieldsplit_pc_type ml \
-stokes_fieldsplit_u_pc_fieldsplit_block_size 3 \
-stokes_fieldsplit_u_pc_fieldsplit_type ADDITIVE \
-stokes_fieldsplit_p_ksp_type preonly \
-stokes_fieldsplit_p_pc_type jacobi \
-stokes_ksp_monitor_blocks \
-mx 16 \
-model 3

gives nicely looking output.

But! Repeating the same exercise with petsc-3.3, like this (actually, 
there is only one difference: factorization -> fact):

mpiexec -np 4 ./ex42 \
-stokes_ksp_type gcr \
-stokes_ksp_rtol 1.0e-6 \
-stokes_pc_type fieldsplit \
-stokes_pc_fieldsplit_type SCHUR \
-stokes-pc_fieldsplit_schur_fact_type UPPER \
-stokes_fieldsplit_u_ksp_type fgmres \
-stokes_fieldsplit_u_ksp_rtol 1e-3 \
-stokes_fieldsplit_u_pc_type fieldsplit \
-stokes_fieldsplit_u_fieldsplit_ksp_type preonly \
-stokes_fieldsplit_u_fieldsplit_pc_type ml \
-stokes_fieldsplit_u_pc_fieldsplit_block_size 3 \
-stokes_fieldsplit_u_pc_fieldsplit_type ADDITIVE \
-stokes_fieldsplit_p_ksp_type preonly \
-stokes_fieldsplit_p_pc_type jacobi \
-stokes_ksp_monitor_blocks \
-mx 16 \
-model 3

curses me hardly by claiming:

[0]PETSC ERROR: --------------------- Error Message 
------------------------------------
[0]PETSC ERROR: Object is in wrong state!
[0]PETSC ERROR: Blocksize of x vector 1 does not match fieldsplit 
blocksize 3!
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.3.0, Patch 0, Tue Jun  5 
14:20:42 CDT 2012
[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: ./ex42 on a int32-deb named mac11-005.geo.uni-mainz.de 
by anton Thu Jun 28 17:06:53 2012
[0]PETSC ERROR: Libraries linked from 
/Users/anton/LIB/petsc-3.3-p0/int32-debug/lib
[0]PETSC ERROR: Configure run at Tue Jun 12 15:32:21 2012
[0]PETSC ERROR: Configure options 
PETSC_DIR=/Users/anton/LIB/petsc-3.3-p0 PETSC_ARCH=int32-debug 
--download-f-blas-lapack=1 --with-debugging=1 --COPTFLAGS="-g -O0" 
--FOPTFLAGS="-g -O0" --CXXOPTFLAGS="-g -O0" --with-c++-support=1 
--with-fortran=1 --with-fortran-kernels=1 --with-large-file-io=1 
--with-mpi-compilers=1 --with-cc=mpicc --with-cxx=mpicxx 
--with-fc=mpif90 --download-ml=1 --download-hypre=1 --download-blacs=1 
--download-scalapack=1 --download-metis=1 --download-parmetis=1 
--download-mumps=1 --download-superlu_dist=1
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: PCApply_FieldSplit() line 726 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/pc/impls/fieldsplit/fieldsplit.c
[0]PETSC ERROR: PCApply() line 384 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPFGMRESCycle() line 169 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/ksp/impls/gmres/fgmres/fgmres.c
[0]PETSC ERROR: KSPSolve_FGMRES() line 294 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/ksp/impls/gmres/fgmres/fgmres.c
[0]PETSC ERROR: KSPSolve() line 446 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCApply_FieldSplit_Schur() line 693 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/pc/impls/fieldsplit/fieldsplit.c
[0]PETSC ERROR: PCApply() line 384 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSolve_GCR_cycle() line 47 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/ksp/impls/gcr/gcr.c
[0]PETSC ERROR: KSPSolve_GCR() line 117 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/ksp/impls/gcr/gcr.c
[0]PETSC ERROR: KSPSolve() line 446 in 
/Users/anton/LIB/petsc-3.3-p0/src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: solve_stokes_3d_coupled() line 2045 in 
src/ksp/ksp/examples/tutorials/ex42.c
[0]PETSC ERROR: main() line 2106 in src/ksp/ksp/examples/tutorials/ex42.c
application called MPI_Abort(MPI_COMM_WORLD, 1) - process 0

Similar error appeared in our code after upgrading to petsc-3.3, and 
we're using similar functionality and options as I posted above.

Please explain this issue. An advice how to get rid of the error is also 
appreciated.

Thanks a lot

Anton