[petsc-users] ODE solving

[Matthew Knepley]

On Thu, Oct 21, 2010 at 5:02 PM, Xuan Yu <xxy113 at psu.edu> wrote:

>
> On Oct 21, 2010, at 5:56 PM, Matthew Knepley wrote:
>
> On Thu, Oct 21, 2010 at 4:46 PM, Xuan Yu <xxy113 at psu.edu> wrote:
>
>> Hi
>>
>>
>> I am using Petsc solve ODE nonlinear problem.
>>
>> I was told to use direct method: umfpackage because of the jacobian matrix
>> is 1860 by 1860.
>>
>> But the time consumption is still too big:
>>
>> TSSetType(ts,TSBEULER)
>>
>> time ./pihm -log_summary -ksp_type preonly -pc_type lu
>> -pc_factor_mat_solver_package umfpack
>>
>> I got the result:
>>
>>
>> When I use TSSetType(ts,TSSUNDIALS), it is fast:
>>
>>
>>
>> How can I find the reason why BEULER is so slow?
>>
>
> You SNES is not converging. You solve 163 systems, but do 4300 function
> evaluations.
>
>
> Could you please tell me more solution options or possible mistakes in my
> code?
>

Jed, is right. You are using coloring with a lot of colors. Sundials is
doing much better
than backwards-Euler, why not just use it?

   Matt


>    Matt
>
>
>> Thanks
>>
>> Xuan
>>
>>
>>
>>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
>
>


-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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