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

[Barry Smith]

  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.
>