[petsc-users] sundials results do not agree with beuler/rosw/pseudo

[Gautam Bisht]

Hi,

I'm solving subsurface flow equation in which the governing ODE is
reformulated as a system of DAE. I'm using PETSc TS+DMComposite to solve
the system with a LU preconditioner. I get comparable results for BEULER,
ROSW and PSEUDO ts_type. But results with SUNDIALS for even a single TS
step are significantly underestimated when compared to those obtained for
the other ts_types. I would appreciate if folks would suggest ideas on how
can I go about figuring out what is going wrong with SUNDIALS.

I'm using following PETSc options:

>/opt/local/bin/mpiexec -n 1 $EXEROOT/cesm.exe \
-ts_monitor \
-ts_view \
-snes_monitor \
-pc_type lu \
-ts_type sundials -ts_sundials_monitor_steps \
-ts_dt 1.0 -ts_final_time 1.0

0 TS dt 1 time 0
1 TS dt 1 time 1
TS Object: 1 MPI processes
  type: sundials
  maximum steps=100000
  maximum time=1
  total number of nonlinear solver iterations=0
  total number of nonlinear solve failures=0
  total number of linear solver iterations=0
  total number of rejected steps=0
  Sundials integrater does not use SNES!
  Sundials integrater type BDF: backward differentiation formula
  Sundials abs tol 1e-06 rel tol 1e-06
  Sundials linear solver tolerance factor 0.05
  Sundials max dimension of Krylov subspace 5
  Sundials using unmodified (classical) Gram-Schmidt for orthogonalization
in GMRES
  Sundials suggested factor for tolerance scaling 1
  Sundials cumulative number of internal steps 1
  Sundials no. of calls to rhs function 2
  Sundials no. of calls to linear solver setup function 1
  Sundials no. of error test failures 0
  Sundials no. of nonlinear solver iterations 1
  Sundials no. of nonlinear convergence failure 0
  Sundials no. of linear iterations 0
  Sundials no. of linear convergence failures 0
  PC Object:   1 MPI processes
    type: lu
    PC has not been set up so information may be incomplete
      LU: out-of-place factorization
      tolerance for zero pivot 2.22045e-14
      matrix ordering: nd
    linear system matrix = precond matrix:
    Mat Object:     1 MPI processes
      type: seqaij
      rows=200, cols=200
      total: nonzeros=598, allocated nonzeros=3200
      total number of mallocs used during MatSetValues calls =200
        not using I-node routines
  Sundials no. of preconditioner evaluations 1
  Sundials no. of preconditioner solves 0
  Sundials no. of Jacobian-vector product evaluations 0
  Sundials no. of rhs calls for finite diff. Jacobian-vector evals 0

Thanks,
-Gautam.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20141103/10a68e8b/attachment.html>