[petsc-users] fieldsplit: Unhandled case, must have at least two fields, not 1!

[Jed Brown]

Mark Adams <mfadams at lbl.gov> writes:
> My point was that this user got this message and so I suggesting a possible
> problem: giving fieldsplit parameters to a single field matrix/solver.

Okay, I interpreted your original statement as being that this error
message has something to do with using monolithic matrix formats (such
as AIJ, versus Nest), which it does not, and that you thought the error
message was problematic behavior.

Your very complicated test case (hundreds of processes, with multiple
solves, some intending to use fieldsplit, Schur, MatNest, tinkering with
the options database, huge differences between the two options files)
can be reduced to src/ksp/ksp/examples/tutorials/ex2.c.

$ ./ex2 -pc_type fieldsplit
[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Petsc has generated inconsistent data!
[0]PETSC ERROR: Unhandled case, must have at least two fields, not 1!
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Development GIT revision: ad348534bf2da17dbc29a6a7895b244965ac0e39  GIT Date: 2013-11-13 12:43:46 -0700
[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: ./ex2 on a mpich named batura by jed Mon Dec  2 09:55:54 2013
[0]PETSC ERROR: Libraries linked from /home/jed/petsc/mpich/lib
[0]PETSC ERROR: Configure run at Wed Nov 13 13:33:49 2013
[0]PETSC ERROR: Configure options --download-blacs --download-chaco --download-ctetgen --download-elemental --download-generator --download-hypre --download-metis --download-ml --download-mumps --download-parmetis --download-scalapack --download-spai --download-spooles --download-sundials --download-superlu --download-superlu_dist --download-triangle --with-blas-lapack=/usr --with-c2html --with-cholmod-dir=/usr --with-cxx-dialect=C++11 --with-exodusii-dir=/usr --with-hdf5-dir=/opt/mpich --with-lgrind --with-mpi-dir=/home/jed/usr/ccache/mpich/ --with-netcdf-dir=/usr --with-openmp --with-pcbddc --with-pthread --with-shared-libraries --with-single-library=0 --with-sowing --with-threadcomm --with-umfpack-dir=/usr --with-x -PETSC_ARCH=mpich COPTFLAGS="-Og -g" CXXOPTFLAGS="-Og -g" FOPTFLAGS="-Og -g"
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: PCFieldSplitSetDefaults() line 441 in src/ksp/pc/impls/fieldsplit/fieldsplit.c
[0]PETSC ERROR: PCSetUp_FieldSplit() line 459 in src/ksp/pc/impls/fieldsplit/fieldsplit.c
[0]PETSC ERROR: PCSetUp() line 888 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSetUp() line 278 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: KSPSolve() line 399 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: main() line 198 in /home/jed/petsc/src/ksp/ksp/examples/tutorials/ex2.c
application called MPI_Abort(MPI_COMM_WORLD, 77) - process 0
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