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

[Gautam Bisht]

Shri: Thanks for pointing out that I need IDA instead of CVODE from
sundials, which isn't currently supported by PETSc. Are there any near term
plans for supporting IDA via PETSc?

Barry: I now realize that PSEUDO is applicable for steady-state problems.
For the time being I will stick with BEULER and ROSW methods and look into
PCFIELDSPLIT.

-Gautam.

On Tue, Nov 4, 2014 at 8:19 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   Note: PSEUDO is a continuation method for solving a nonlinear system, it
> doesn’t make sense to use it to replace other methods.
>
>   That time step of 1 seems very large for SUNDIALs to be using
>
>   Barry
>
> > On Nov 4, 2014, at 9:40 AM, Abhyankar, Shrirang G. <abhyshr at mcs.anl.gov>
> wrote:
> >
> > PETSc only supports the ODE solver (CVODE) from Sundials.
> >
> > Shri
> >
> > From: Gautam Bisht <gbisht at lbl.gov>
> > Date: Mon, 3 Nov 2014 22:56:58 -0800
> > To: <petsc-users at mcs.anl.gov>
> > Subject: [petsc-users] sundials results do not agree with
> beuler/rosw/pseudo
> >
> > 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.
> >
>
>
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